5 Hot days are defined as the number of days each summer that daily maximum temperature (Tx) exceeds 31 o C (close to the 95 th percentile).

First and foremost, I want to thank my family who has been my foundation throughout my entire educational career. To two loved and respected educatorsmy grandfatherswho instilled our drive. My dad, all your support and encouragement from the very start has been unparalleled and you are my greatest role model. Mum, there is no one like you in this world, and there never will be. I am thankful for you every day. Your unconditional love is a gift to me and I aspire to have the strength that you have every day, especially in the face of personal struggles. Thank you for believing in me. My dearest sisters, Garene and Talar, your emotional support helped me through long hours of writing, rewriting and rewriting. You were my rocks. To my husband Harout, thank you for your unconditional support, for your patience and encouragement, especially at times when I was struggling most. And let's not forget my two treasures and angels, Lila and Alec who, although would continuously ask me when my "assignments" would end, would also encourage me to finish quickly while sitting not so patiently on my lap.

To Dominique Tohme, my brother-in-law, and Marc Geara, a dear friend, thank you for your help in my attempt to master the French language.

Certainly Yousef Diab, I thank you for your endless support, continuous motivation and encouragement. Your exemplary guidance through your constructive feedback and yet positive attitude was unsurpassed. Hassãn Bitar, you challenged me to reach my maximum capacity of delivery and productivity, and for this I am truly grateful.

To Paula Samaha also, for your encouragement, I thank you.

Valéry Masson, your unmatched support throughout the process of my research was most sincerely appreciated. Aude Lemonsu, considering your extremely busy schedule, and not to mention your personal agenda, you still dedicated a substantial amount of time to help me perfect my research and for that I am truly grateful.

To Ali Msallem and Wissam Katerji I thank you for your unparalleled support in helping me to master the ArcGIS software. To Jobran Hammoud, my close friend and colleague you were without doubt the greatest support throughout the full four years of my PhD venture and for that I thank you most sincerely. My dearest friend and colleague Rodolf Ghoussoub, you personally and painstakingly worked with me and helped me progress with my research work well into the wee hours of the morning. Thank you! Vahakn Kabakian, my friend and colleague, your support throughout this process in providing any necessary information was invaluable. Sami Ibrahim, my friend and colleague, you provided me with endless amounts of crucial data. Abood Hajjar and Martin Hendel, my enthusiastic colleagues, I thank you for your continuous support, even amid your busy schedules. Morgane Colombert, I thank you for your dedicated time and guidance especially during my trips to Paris. Pierre El Khoury, your valuable contribution was and will always be truly appreciated. To a friend and colleague Dr. Christine Mady who introduced me to this program from the start and of course I could not forget Dr. Jala Makhzoumi, a dear colleague who encouraged me most sincerely to start this program, given my not so easy personal circumstances.

And finally, I thank the following institutions without which this project would and the Lebanese Center for Energy Conservation (LCEC). I am hopeful that our work together will better the quality of life for the residents of our country, and set an example to neighbouring countries.

Abstract

Replacement of natural surfaces with artificial surfaces, anthropogenic heat emissions and urban geometry can lead to one of the more widely documented phenomena of climate change known as the urban heat island (UHI). In Beirut, there is no evidence that the UHI has been investigated or even considered in relevant policies or construction standards.

In this research, the UHI is investigated across Beirut to find the most suitable mitigation solutions within urban planning and design disciplines. The methodology adopted included using the Town Energy Balance model of Météo France [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] which parameterizes the surface-atmospheric energy exchanges. Simulations determined that raising the solar reflectance of roof materials had the highest impact on alleviation of the UHI followed by increasing garden fractions.

Improvements could be made in the Urban Planning Law #69 (dated 1983), the Building Code #646 (dated 2004) and the existing institutional framework to ensure protection of the urban microclimate. Transfer of urban climatic knowledge amongst all relevant stakeholders could also be beneficial in this regard. Indeed, TEB could be an important decision-making tool and a means to promote evidence-based planning and design practices in Beirut.

Limitations included limited data availability, which were accordingly extrapolated using aerial imagery. TEB also requires simplified architectural data requirements and does not have the option to include street orientations in its simulations.

Future research could include investigation of the impacts of cooling by increasing evaporation, and cooling by implementation of water-film surfaces, as well as the investigation of the actual possibility of intervention and implementation of proposed mitigating actions for Beirut, taking into consideration economic and social conditions. Key words: Urban Heat Island, Beirut, Town Energy Balance, Urban Planning, Building Code

Résumé

Le remplacement des surfaces naturelles par des surfaces artificielles, les émissions de chaleur anthropique et la géométrie urbaine peut résulter au phénomène plus ou moins documenté du changement climatique, aussi connu sous le nom de l'Ilot de Chaleur Urbain (ICU). il n'y aurait pas de preuves que ce phénomène a été le sujet d'enquêtes approfondies ou même encore pris en considération dans l'élaboration des politiques nationales relatives ou des standards de construction.

Dans cette étude, le ICU sera le sujet d'enquête à travers Beyrouth afin d'identifier les solutions atténuantes au sein même des disciplines de planification urbaine et de la conception. La méthodologie adoptée inclue l'utilisation du model Town Energy Balance de Météo France [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] qui fournit des paramètres sur l'échange d'énergie entre les surfaces et l'atmosphère. Les simulations ont déterminé que l'augmentation de l'aptitude de réflexion solaire des matériaux des toits est le facteur le plus important sur la réduction de l'ICU dans la ville de Beyrouth, suivit par l'augmentation des espaces verts.

Des améliorations pourraient être introduites à la loi sur la planification urbaine 69 de 1983, le code de construction 646 de 2004 et le cadre institutionnel existant pour assurer la protection du microclimat urbain. Le transfert de connaissance sur le climat urbain entre les différents acteurs pourrait aussi être bénéfique à ce sujet. Au fait, TEB pourrait être un outil de prise de décision important et un moyen pour promouvoir une planification fondée sur les preuves et des pratiques de conception à Beyrouth.

Les limites dont a souffert cette étude ont été les informations disponibles limitées, qui ont été tout de même extrapolées à travers l'utilisation de l'imagerie aérienne. Le EVV requit aussi des exigences d'information architecturale simplifiées et ne fournit pas l'option d'inclure le sens des rues dans la simulation.

Les recherches à l'avenir pourraient inclure des enquêtes sur l'impact du refroidissement à travers l'augmentation de l'évaporation et le refroidissement à travers l'installation de surfaces de films d'eau, ainsi que la considération de la possibilité pratique d'intervention et la mise en place des mesures d'atténuation suggérées pour Beyrouth, en prenant en considération les conditions socio-économiques.

Mots clés : L'îlot de chaleur urbain, Beyrouth, Town Energy Balance, planification urbaine, loi sur la construction. (pav, cova, bare, nat, roof, vega, ven, wat) and 3 layers of soil. (b) Energy budget of paved surfaces. Source : Mestayer, et al., 2004, pp. Table 1: Five weather types based on variations of wind speed cloud cover adapted from [START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] In this introductory chapter of this thesis, background information on the country of Lebanon and its capital city of Beirut is given. This includes, existing and projected urban populations, urbanization and impacts on the surrounding environment and urban microclimate or more specifically on the urban heat island (UHI) phenomenon, which is the context of this research. As such, the significant impacts of the UHI related to human health, deterioration of the quality of life and heat-related mortality is deliberated which justify the need to conduct detailed research and analysis for the densely populated city of Beirut. The choice of scale at which the data collection and numerical analysis of this research is carried out is also discussed. Finally the research objectives and the thesis structure are all outlined in this chapter.

Table of Contents

List of Figures

List of Tables

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Background Information on Lebanon

Lebanon is the second smallest country in the Middle East after Bahrain, covering an area of 10,452 km 2 with an estimated local population of about 4, 223,553 (World Bank, 2013). The urban density1 is one of the highest in the world with an estimated ratio of about 21,000 inhabitants / km 2 (Population and Development Strategies Programme Lebanon, 2014; MOE/LEDO/ ECODIT, 2001). Latest available figures show that 87 % of actual population lives in urban to suburban 2 areas of which 64 % resides in large urban agglomerations namely in the cities of Beirut, Tripoli, Sidon, Tyr and Baalbek (United Nations Centre for Human Settlements [UN-HABITAT], 2009). This is by far the highest urban to rural population in the region ahead of Jordan (78.5 %) and Syria (54.6 %).

According to UN-HABITAT (2011), the Lebanese population is expected yet to grow to reach 4,587,000 capita by year 2020, of which 89 % will be an urban population.

Therefore, built environment or built-up areas3 are also expected to grow accordingly over the next 3 decades at a rate of 10 km 2 /year (CDR-NPMPLT/DAR-IAURIF, 2004).

Urbanization Effects on UHI and implications for Beirut city

Urban populations are increasing due to rural exodus, which is a growing trend worldwide and which is generally found to be the result of a combination of factors including greater job opportunities, wider choices in education, improved infrastructure, and higher expectations in overall quality of life, and for the case of Beirut, due to the combined effect of an influx of refugees. Urban areas consequently become major consumers of energy and materials generating vast amounts of harmful waste such as carbon dioxide (CO 2 ), from the burning of fossil fuels for heating and cooling purposes, industrial processes, and transportation of people and goods. Although there is much contention on this issue, they contribute to a certain extent to greenhouse gas (GHG) forced global climate change [START_REF] Emmanuel | Urban heat island and its impact on climate change resilience in a shrinking city: The case of Glasgow, UK[END_REF][START_REF] Grimmond | Urbanization and global environmental change: local effects of urban warming[END_REF].

Urban areas also contribute to urban microclimate effects at the city scale.

Therefore, increasing urban populations are also responsible for the gradual modification of surfaces at city scales where natural vegetation is replaced with buildings and roads [START_REF] Akbari | Potentials of urban heat island mitigation. Prepared for: International Conference on Passive and Low Energy Cooling for the Built Environment[END_REF]. As such, the urban microclimate is affected. The term Urban Heat Island (UHI) describes this phenomenon which is related to higher urban temperatures in the city centers as compared to the surrounding rural or suburban areas (Figure 1). The UHI phenomenon is mainly related to the high density of buildings and urban structures that absorb solar radiation, the use of highly absorbing materials, the lack of green spaces, the characteristics of the urban canyons, and the production of anthropogenic heat [START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF]. In fact, research studies conducted in the Mediterranean region other than Beirut, like in the city of Athens for example, have

shown the strong positive correlation that exists between the aforementioned parameters and the UHI [START_REF] Giannopoulou | On the characteristics of the summer urban heat island in Athens, Greece[END_REF][START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF][START_REF] Santamouris | Using cool paving materials to improve microclimate of urban areas -Design realization and results of the flisvos project[END_REF]. Urban densification therefore increases the proportion of impervious artificial4 surfaces and changes the urban fabric morphology [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF] resulting in higher urban temperatures. While predicting climate change and its impacts at a global scale is still highly uncertain, the effects of urbanization on the climate at the city scale have long been recognized and documented [START_REF] Landsberg | The Urban Climate[END_REF][START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. The question of what the repercussions of urban heating are on city dwellers therefore arises. Indeed it has been found that urban heating may cause many problems for urban populations including deteriorating living environments and associated qualities, increasing energy consumption, growing health concerns, and even rises in mortality rates (Rizwan, Dennis, & Chun-Ho, 2009) as in the case of the summer 2003 heat wave, which resulted in an estimated 70,000 additional deaths in Europe. In France alone, which was hit the hardest, approximately 14,000 heat-related deaths occurred during the 2003 summer heat wave according to the French National Institute of Health [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF][START_REF] Chagnon | Impacts and responses to the 1995 heat wave: a call to action[END_REF] French Institute for Public

Health Surveillance [INVS], 2015; [START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF][START_REF] Meehl | More intense, more frequent, and longer lasting heat waves in the 21 st century[END_REF][START_REF] Poumadère | The 2003 heat wave in France: dangerous climate change here and now[END_REF]. Settlements are continually expanding to accommodate the influx of migrants from rural areas not to mention the natural increase of urban populations. This makes the study of urban climates doubly important; first to ensure a pleasant and healthy environment for urban dwellers, and second to see that the effects of urbanization do not have harmful repercussions on larger scale climates [START_REF] Oke | Boundary Layer Climates. 1st Edition[END_REF]. For the case of Beirut city, which as previously mentioned is experiencing rural exodus, and associated developments and constructions, not to mention major traffic congestions, dramatic impacts on the UHI are increasing which is why it is imperative to conduct a detailed investigation and analysis of this phenomenon in Beirut and find mitigating solutions in urban planning policies and practices.

Scale of Study for Beirut City

The complex morphology of urban areas results in a range of effects on the surface-atmosphere energy exchange balance. In order to understand the physical mechanisms responsible for the urban modifications to the local climate it is necessary to first comprehend the spatial scale upon which these physical processes act. According to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF], there are four classifications of scales in which atmospheric phenomena can occur; these include micro-scale (10 -2 to 10 3 m), local scale (10 2 to 5 x 10 4 m), meso-scale (10 4 to 2 x 10 5 m) and macro-scale (10 5 to 10 8 m ) classifications. This research focuses on the effects of urbanization in Beirut at the city scale or meso-scale level, while microscale essentially refers to street level, local scale to neighborhood level and macro-scale to larger regional levels.

It is worth noting that a key aspect of urban meteorology studies concerns the description and classification of the surface on the relevant spatial scale which is why it is important to first identify the scale at which the research will be conducted. Therefore, the meso-scale level of study is selected because the aim of this research is to identify urban parameters that have the most significant impact on UHI at the city-scale of Beirut in the view to propose mitigation measures from an urban planning perspective for the city.

Research Objectives

This research therefore aims to investigate the UHI phenomenon within the Beirut In this chapter of the thesis, a detailed account of the history and definition of the urban heat island is provided as well as the different types of heat islands that exist, such as the urban canopy layer, the urban boundary layer and the surface heat islands, all based on the available literature on the topic. In addition, this chapter discusses the underlying causes that lead to the formation and exacerbation of the heat island, namely natural factors such as geographic locations, proximity to major water bodies, climatic conditions and so on, and anthropogenic factors such as industrial and traffic-associated heat emissions, as well as urban geometry of cities, solar reflectivity of urban materials and presence or absence of vegetation.

History and Definition

In 1818 phenomenon that was later coined as the "Urban Heat Island (UHI)".

Similar observations were then made in Paris in the second half of the 19th century, in Vienna in the early 20th century, and in the U.S. in the first half of the 20th century [START_REF] Gartland | Heat Islands: Understanding and Mitigating Heat in Urban Areas[END_REF]. Thereafter, several investigations have been made uncovering the causes that contribute to the UHI effect, putting forth various methods to modeling the UHI, and suggesting effective measures to mitigate and alleviate the negative impacts of UHI on cities and their dwellers.

The term "heat island" therefore describes urbanized areas that are hotter than nearby non-urbanized areas due to the fact that urban areas have typically darker surfaces and less vegetation than semi-urban and non-urban surroundings. This difference in daily temperatures between urban and non-urban areas affects not only the microclimate but also the energy use and habitability of cities. At the building scale, dark roofs heat up more, thus increasing the summertime cooling demands of buildings. For example, a study conducted in the city of Athens, with an urban heat island intensity of 10 o C, showed that the cooling load, or cooling energy demand, of urban buildings may be doubled thus reflecting the strong impact of the UHI on energy demands in urbanized areas [START_REF] Santamouris | On the impact of urban climate on the energy consumption of buildings[END_REF]. Similar effects can be expected in Beirut due to the resemblances in urban characteristics between these two Mediterranean cities. Moreover, dark surfaces and lack of vegetation collectively warm the air over urban areas leading to the creation of urban heat sinks. It has been reported, that on a clear summer afternoon, the air temperature in a typical city is as much as 2.5 o C higher than in the surrounding rural areas [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF].This urban heating or UHI can therefore also result in mortality like in the case of the 2003 summer heat wave in Paris which caused over 10,000 heat-related deaths as recorded by the French National Institute of Health thus reflecting the strong impact of the UHI on human health and quality of living in urbanized areas (INVS, 2015). In Beirut, the number of hot days 5 has increased during the second half of the last century, at a rate of about two days per decade. In fact the largest number of hot days has been recorded from the late 1980s onwards, during which time urbanization developments and urban population records in Beirut increased significantly making the living thermal conditions extremely uncomfortable and unhealthy for the city dwellers. Hot summer days can accordingly have negative effects on human comfort levels and can contribute to significant heat stress. The number of hot summer days has increased significantly in Beirut in this past decade (Hatzaki, Giannakopoulos, Hadjinicolaou, & Kastopoulou;CIRCE project, 2010), which lowers thermal comfort levels dramatically consequently affecting human health and overall quality of life (this is described in more detail in Part III of this thesisclimatic conditions).

Types of heat islands.

Looking closely at this phenomenon, [START_REF] Oke | The energetic basis of the urban heat island[END_REF] distinguished 3 types of heat islands; these are: the urban canopy layer (UCL), the urban boundary layer (UBL), and 40 the surface heat island (SHI). It's important to distinguish between these different heat islands as their underlying mechanisms are also different. The first two layers refer to a warming of the urban atmosphere and are referred to as "atmospheric urban heat islands" whereas the last refers to the relative warmth of urban surfaces (see Figure 3). The UCL is the layer of air closest to the surface in cities, extending upwards to approximately the mean building height. It is in fact within this layer, the urban canyon layer, in which numerical analysis for this research is carried out by using the Town Energy Balance (TEB) urban surface exchange model developed by [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] which aims to realistically represent the energy balance of the 3-dimensional urban canyon representing roofs, walls and roads [START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF] (see Chapter 3 for more details on existing modeling tools of the urban heat island).

Above the urban canopy layer lies the UBL, which varies in thicknesses from 1 kilometer or more during the day to hundreds of meters or less at night. It is a domeshaped heat sink of warmer air that extends downwind of the city which may sometimes take a plume shape depending on the wind gust. Atmospheric heat islands are typically weak during the late morning and throughout the day but become more pronounced after sunset due to the slow release of heat from urban mineralized surfaces. Also, atmospheric heat islands vary much less in intensity than SHIs. On an annual mean basis, air temperatures in cities might be 1 to 3 o C warmer than their rural surroundings. On the other hand, SHIs are typically present throughout the day and night but tend to be strongest during the day. On average, the difference in daytime temperatures between urban and rural areas is about 10 to 15 o C while the difference in surface temperatures during the nighttime is typically smaller, between 5 to 10 o C showing therefore a greater intensity than atmospheric heat islands (USEPA, 2014).

It is also worth noting that heat islands may vary in spatial form or shape, in temporal characteristics, and in some of the underlying physical processes that contribute to their development. Air temperatures at the UCL and UBL are measured directly using thermometers; whereas, the SHI is measured either indirectly using remote sensing techniques and technologies or directly through handheld or aircraft mounted thermal scanners [START_REF] Voogt | Urban heat islands: hotter cities[END_REF].

Therefore, out of the three types of urban heat islands identified, this research focuses on the urban canyon layer (UCL). More specifically, investigations in this research within the context of Beirut are concentrated on the effects of the various complex interactions of the existing urban conditions on the urban heat island air temperatures, as opposed to surface temperatures or boundary layer air temperatures, in the urban canyon layer. A canyon is defined as a street which is flanked on both sides by buildings and therefore investigations in an urban canyon layer extends upwards to the average building height in a street. This specific layer was selected since the purpose of this research is to ultimately find mitigation solutions to ensure the thermal comfort of the urban dwellers who are more directly affected by air temperatures within the canyon layer in which they frequent as opposed to the boundary layer. While surface temperatures may also have an impact on surrounding air temperatures, measurements for urban surfaces require thermal remote sensing data which is somewhat limited for Beirut city as explained in more detail in Chapter 4 of this thesis.

Causes of the Heat Island

There is no single cause of the heat island phenomena. Instead, many factors combine to increase urban and suburban temperatures including 1) meteorological or natural factors and 2) urban or anthropogenic parameters examples of which are described in more detail as follows:

1) Meteorological parameters such as temperature, cloud cover and wind have a significant impact on the UHI. The natural location of a city also plays a role since its physical characteristics that include topography, mountain ranges and hills, rivers and/or other water bodies can determine the extent to which UHI can be affected.

2) As for anthropogenic factors, these include urban parameters such as city size, influenced by urban populations and densities, density of built-up areas including land coverage, distance between buildings and average height of buildings, urban geometry that includes street orientations, aspect or height (H) to width (W) ratio (H/W) of buildings, and sky view factor (SVF), which is the visible area of the sky from a given surface. Other urban parameters that exacerbate the UHI include man-made surfaces including buildings and pavements that are generally composed of dark materials that readily absorb and store the sun's heat. Most building materials are also impermeable thus further exacerbating the warming trend in cities. Other man-made reasons for the heat island formation include urban heat generations as well as high levels of urban air pollution. These natural and man-made causes of the heat island, which are relevant for the Beirut case, are described in more detail in the following sections.

Natural factors.

Meteorological factors such as winds and cloud cover also have an impact on the development of UHI. For instance, during periods of calm winds and clear skies, UHI may be intensified by the amount of solar energy retained by urban surfaces which is not easily convected away from the city, whereas the opposite effect occurs during periods of strong winds and increased cloud cover (Che-Ani, [START_REF] Shahmohamadi | Mitigating the urban island effect: some points with altering existing city planning[END_REF]. [START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] defined five weather types based on variations of wind speeds and cloud cover (see Table 1) and found that the UHI is more intense under conditions of atmospheric stability than under conditions of instability. Cloud cover and wind speed can also exacerbate the UHI by intensifying pollution and smog episodes in cities since particles in the air absorb and emit heat to a city's surfaces.

The time of day can also affect the UHI intensity. [START_REF] Oke | The energetic basis of the urban heat island[END_REF] and [START_REF] Voogt | Urban heat islands: hotter cities[END_REF] demonstrated that the heat island intensity increases from the sunset hours till the predawn and typically reaches its maximum values when the temperature is at a daily minimum [START_REF] Karl | Urbanization: Its detection and effect in the United States climate record[END_REF]. [START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] also studied the intensity of the UHI during a three year period between 1996 and 1998 in the city of Salamanca in Spain comparing the temperatures in an urban area and those in a nearby rural area and found that the UHI is more intense during the night-time hours. A similar study carried out in Athens which studies the hourly variability of the UHI effect also shows that the hottest temperatures are recorded in the afternoon hours [START_REF] Kourtidis | A study of the hourly variability of the urban heat island effect in the Greater Athens Area during summer[END_REF]. It is expected that Beirut city would have similar variability of the UHI effect during the day.

This is attributed to the fact that the city of Beirut has urban characteristics similar to those of Athens; they are both coastal situated along the Mediterranean Sea, they are both characterized by a dense built environment with mainly artificial dark urban surfaces, few green or natural spaces, major road networks, a skyline that is gradually changing with the construction of newer and taller buildings6 , and both are densely populated (Beirut has a population density of about 21,000 persons/km 2 while Athens has a population density of about 23,000 persons/km 2 ). Indeed this research aims to investigate the UHI effect in the city of Beirut in the view to identify the urban parameters that have the most significant effect on the UHI diurnal variability and to consequently find mitigating solutions from an urban planning and design perspective (see Part IV of this research).

Therefore the available literature shows that the natural factors that characterize a city play an important role on impacting the UHI. For the case of Beirut, which is a coastal city and which is characterized by a relatively flat topography with two hill-tops at 90m elevations above sea-level (A.S.L.), and a mild winter season with typically low average wind speeds throughout the year, the UHI effect can be exacerbated especially when these natural factors are combined with the existing artificial (as opposed to natural) urban fabric and the characteristic geometry of the city (see subsequent sections).

The natural factors characterizing the city of Beirut, namely the defining weather characteristics like minimum and maximum temperatures and wind speed and so on, are described in more detail in Part III of this thesis. Furthermore, [START_REF] Landsberg | The Urban Climate[END_REF] posits that the heat island is present in every town and city and is the most obvious climatic manifestation of urbanization (as cited in Santamouris, 2013, p. 48). Beirut city also falls under this category especially when considering the considerable rise in city residents during the last fifty years and the respective high fraction of impermeable and mineralized urban surfaces (see Part III case study for Beirut). To this effect, the impact of urbanization on long-term temperature records has been observed for cities with populations less than 10,000 even [START_REF] Karl | Urbanization: Its detection and effect in the United States climate record[END_REF]. Urbanization therefore results in changes in land uses and practices thus affecting the intensity and scale of the UHI formation. For example, industrial areas, with their anthropogenic heat emissions, can have significant exacerbating effects on the UHI while residential areas with large open spaces would potentially have much lower impacts on the UHI.

In fact, [START_REF] Rizwan | A review on the generation, determination and mitigation of Urban Heat Island[END_REF] highlighted the significant role of anthropogenic heat on UHI, while [START_REF] Emmanuel | Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA[END_REF] highlighted anthropogenic heat or heat waste from combustion and metabolism as being one of the major contributors to urban microclimate modifications. In another similar study, [START_REF] Giannopoulou | On the characteristics of the summer urban heat island in Athens, Greece[END_REF] showed that increased urbanization, industrialization and increased anthropogenic heat all play a significant role in exacerbating high urban temperature trends and accordingly urban heat islands. In this aforementioned study, the characteristics of the UHI phenomenon were analyzed during the summer season by using 25 fixed temperature stations which were spread out across the major Athens area. The city was then divided into five geographic zones where higher air temperatures were found in the western industrial part of the city and the center, where anthropogenic heat emissions are highest, while lower values were found in the less urbanized areas in the northern and eastern parts. Another study conducted in Athens [START_REF] Katsoulis | Indications of the urban heat island in Athens, Greece[END_REF], showed similar results to those of [START_REF] Giannopoulou | On the characteristics of the summer urban heat island in Athens, Greece[END_REF], and indicated a close correlation between growth of the city and the UHI effect.

Beirut is city in the Mediterranean region, with similar urban characteristics to those of Athens, namely the very dense built-up areas, the high population concentrations within the city, and the high traffic congestion, which can all also contribute to an intense urban heat island effect when compared to the more rural, and less populated and congested surrounding areas.

Urbanized and dense city centers characterized by tall buildings and high traffic volumes will also add to the intensity of the UHI as seen for example in the works of [START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] in the city of Salamanca, who found maximum temperature records in areas characterized by higher percentage of built-up area while the opposite was found in areas with a much higher percentage of green areas. These higher urban temperature trends are attributed to increasing urban populations, urbanization trends and corresponding generation of anthropogenic heat.

Therefore urbanization and anthropogenic heat sources have been found to have significant impacts on the UHI effect according to the available literature. The city of Beirut, which is a dense city with many road networks, significant traffic congestion, and haphazardly located industrial areas which generate uncontrolled and high levels of air polluting emissions (MOE/UNDP/ECODIT, 2011), is without doubt a major source of anthropogenic heat emissions. However this research focuses primarily on the artificial urban surfaces and their respective impacts on the UHI in Beirut as opposed to anthropogenic heat sources since the aim of this research is primarily to identify the urban planning and design schemes that can be modified or corrected in future sustainable planning solutions for the city. Having said this, the effects of anthropogenic heat on the UHI in Beirut can be a potential topic of research to be considered in future works for the city.

Albedo and urban surface materials.

Another significant anthropogenic factor that has a major impact on the UHI phenomenon is the albedo property of urban surface materials. Simply put, the "albedo" -from Latin "albus" meaning whiteness -is the ratio of the amount of light or energy that is reflected back into the atmosphere by any particular surface. A low albedo means a surface reflects a small amount of the incoming radiation and absorbs the rest, for example for trees the albedo (α) is between 0.15 and 0.18. On the other hand, a high albedo means a surface absorbs a small amount of the incoming radiation and reflects the rest, for example a white paint albedo (α) may range between 0.5 and 0.95 (see Table 2). Therefore, depending on the type of urban material and its associated albedo property, the UHI phenomenon can be affected significantly.

The albedo value of mineralized surfaces in a typical city is typically low. This is because cities are usually composed of tall and medium-sized buildings which have dark concrete surfaces. Access roads and transportation networks in these cities also tend to be comprised of similar materials. These dark hard impermeable surfaces, including stone, concrete and asphalt that typically replace the vegetative surfaces (also resulting in changes in land use) are usually characterized as "warm" materials, have low "albedo" or reflective properties with high heat retaining properties, and typically result in higher urban temperatures as compared to their surrounding rural areas.

Thus urban surfaces with particular geometrical effects, multiple reflections, or with darker colours, intensify the UHI. In turn it is possible that "higher urban air temperatures increase city-scale cooling loads as well as the frequency of smog episodes" [START_REF] Taha | High-Albedo materials for reducing building cooling energy use[END_REF]. Therefore, by taking into consideration the albedo properties of urban surface materials in urban design and planning measures including roofing or paving, there can be better control over urban microclimates and energy consumption, resulting in an overall improved quality of life [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF]Rosenfeld, Akbari, Bretz, Fishman, Kurn, Sailor, and Taha, 1998;Synnefa, Saliari, and Santamouris, 2013;[START_REF] Taha | High-Albedo materials for reducing building cooling energy use[END_REF][START_REF] Taha | Urban climates and heat islands: albedo, evapotranspiration, and anthropogenic heat[END_REF]. As such, in order to implement sustainable urban designs that have optimal impacts on the microclimate and UHI, it is necessary to calculate the albedo values of typical urban materials. The available literature gives light to certain studies carried out in this regard that propose new computer web based applications for example as well as systems to calculate the albedo properties of urban surface materials [START_REF] Chimklai | A computer system to support albedo calculation in urban areas[END_REF][START_REF] Tsangrassoulis | Numerical estimation of street canyon albedo consisting of vertical coated glazed facades[END_REF].

Other studies investigate the impact of weathering and cleansing on the albedo values of existing urban materials (such as roofing and paving materials) and consequently on the climatic conditions of urbanized area. For instance, Berdahl, Akbari, [START_REF] Berdahl | Weathering of roofing materialsan overview[END_REF] and [START_REF] Levinson | Effects of soiling and cleaning on the reflectance and solar heat gain of a light-colored roofing membrane[END_REF] assessed the albedo effects and thermal properties of roofing materials, in weathered, clean and soiled conditions. They found that roofing materials in an unweathered and clean state were cooler than the same materials in soiled and weathered conditions. Furthermore, [START_REF] Doulos | Passive cooling of outdoor urban spaces. The role of materials[END_REF] and [START_REF] Asaeda | Heat storage of pavement and its effect on the lower atmosphere[END_REF] assessed the albedo values and associated thermal properties of paving materials of different colours, textures, and sizes and confirmed that light coloured surfaces are cooler than dark coloured surface. Whereas, [START_REF] Asaeda | Heat storage of pavement and its effect on the lower atmosphere[END_REF] found that heat storage for asphalt was significantly higher than that for concrete or bare soil. In Beirut, asphalt is the main material used in road surfaces. Thus, as per [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF], considering the very low albedo property of this material, the limited urban vegetated surfaces and the existing dense urban fabric, the impacts on UHI can be felt ever more clearly, which is why it is important to conduct in-depth investigations that can indicate and determine these impacts clearly in the view to find good mitigative solutions.

In addition, many studies have been carried out to measure the temperature of urban surfaces to determine their effect on the UHI. [START_REF] Doulos | Passive cooling of outdoor urban spaces. The role of materials[END_REF] used an infrared camera to measure the surface temperature of urban paving materials as well as a precise contact thermometer in order to take into account minor errors associated with the infrared thermography procedures. [START_REF] Hendel | Improving a pavementwatering method on the basis of pavement surface temperature measurements[END_REF] also used infrared camera measurements of pavement surface temperatures in their study on the potential use of pavement-watering methods to mitigate the urban heat island phenomenon in the city of Paris. [START_REF] Asaeda | Heat storage of pavement and its effect on the lower atmosphere[END_REF] on the other hand showed the temperature distribution in pavements using experimental procedures that involved installing 1mm diameter copper tubes along the central axis of pavement samples (including asphalt and concrete slabs, and bare soil) through which thermocouples were inserted. [START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF] assessed in detail the thermal performance and benefits of materials for buildings and urban structures with high solar reflectance and infrared emittance, "cool materials", such as cool roofing materials, cool-paving materials, phase change materials (PCM), and thermo-chromic materials and found that materials with high reflectivity and high emissivity contribute highly to UHI mitigation.

In a similar study, Synnefa, Santamouris and Livada (2005) investigated 14 types of reflective coatings which are commonly used in the urban environment's external surfaces, like building walls and roofs, sidewalks, pavements, and parking lots, and with the use of surface temperature sensors, and infrared thermography procedures, they were able to demonstrate that the use of reflective coatings with high solar reflectance properties, can significantly reduce surface temperatures.

Therefore the available literature shows that techniques used to measure temperature distribution of urban surface materials are diverse and help to determine albedo properties of construction materials used for urban surfaces including paving, roofing and facades. While this technique is not applied for this research, since the available literature on albedo properties for specific materials is abundant and generally unanimous, it can be considered as a potential future approach to more accurately determine the solar reflectivity or albedo of the urban materials in the city of Beirut.

In addition, the available literature points to the fact the use of low reflective cool materials (for example for facades, rooftops and roads) is considered the norm nowadays for a sustainable architecture, design and planning of cities in hot climatic zones and this can also be considered for the Beirut context. Indeed, Beirut is a city which is characterized mainly by low albedo urban surfaces for rooftops and road surfaces (see Part III -Beirut Case Study for more details on the land cover land uses and albedo values of dominating urban surfaces within the Beirut context). Therefore the albedo or solar reflectivity of an urban material is a very important factor that needs to be considered when devising sustainable solutions for mitigation of the UHI impact in a city (see Chapter 4 on mitigation measures). [START_REF] Lindberg | Urban geometry and temperature variations[END_REF][START_REF] Ando | Effects of urban geometry on urban heat islands in Tokyo[END_REF]. It refers to the shape, dimension and spacing of buildings within a city, which together add to the amount of radiation received, reflected and emitted by the urban infrastructure. In urbanized areas, spaces and structures are often obstructed, either fully or partially, by building blocks that quickly become large thermal masses triggering the build-up of UHI (EPA, 2014). [START_REF] Shahmohamadi | Mitigating the urban island effect: some points with altering existing city planning[END_REF] found that development of UHI is sometimes partially due to unplanned urban geometries. This section describes the importance of the effects of building heights, sky view factor, height to width ratio and street orientations on the UHI impact. Another important aspect of urban geometry which is frequently studied is the sky view factor (SVF) described as the ratio of the amount of the sky 'seen' from a given point on a surface to that potentially available (i.e. the proportion of the sky hemisphere subtended by a horizontal surface). Therefore an urban canyon that is characterized by tall closely spaced buildings would have a low SVF as opposed to an open space parking lot or field with few obstructions which would accordingly have a high SVF. As such, during the night-time, due to dense developed areas characterized by low SVF, urban areas cannot easily release radiation into the cooler open sky and therefore this trapped heat contributes to the urban heat island. Oke (1981) used the SVF to characterize the urban geometry of a city by using the following formula:

Height and

ΔT max = 15.27 -13.88*SVF ( o C) (Equation 1)

This formula assumes that the urban heat island effect is due mainly to the reduced heat loss in narrow streets compared to more open environments. In a study on urban design factors that have the greatest influence on heat island intensity in high-rise high-density environment of Hong Kong, 12 variables were used 7 , including the SVF, for 17 coastal area residential developments. Figure 4 shows images of these 17 coastal developments where the measurements were carried out showing the close relation between SVF and UHI. In this study therefore, statistical method analysis was carried out to identify the most critical variables that can be used to mitigate UHI in high-rise highdensity environments. Among other variables like albedo, altitude and vegetation, it was found that the SVF is a critical variable in mitigating both daytime and nocturnal UHI (Giridharan, Lau, Ganesan, and Givoni, 2007). For the case of Beirut, the average height of buildings is about 15-18m (or 6-storeys high) although this trend is currently being altered due to limited land space availability within the city with a resulting rise in the average height of buildings which could potentially lower the SVF and thus trap more heat in the canyons and accordingly exacerbate the UHI. Indeed old buildings are being demolished and replaced by taller and more modern buildings, such as in Ashrafiyeh and

Ras Beirut areas 8 which can potentially have significant impacts on the UHI of the city.

Therefore, the SVF is not assumed to play a significant impact on the UHI in Beirut at the present time although given the limited land availability and increased demand for housing this may change in the near future with the resulting construction of taller 7 Other variables included solar radiation intensity, wind velocity, average height (H) to floor area (A) ratio (HA), surface albedo (SA), altitude, and proximity to sea, vegetation below and above 1m in height, total non-residential to total floor area ratio, location quotient (is an analytical statistic and is a way of quantifying how concentrated a particular industry, cluster, occupation, or demography group is in a region as compared to the nation), emission index-day, and emission index night.

8 Refer to Part III on "Beirut Case Study" of this thesis which identifies the administrative areas of Beirut and the respective geographical locations of these areas.

buildings throughout the city. It is worth noting however that this factor is not considered as a scenario in the numerical analysis chapter of this research since the modification of the height of buildings has already been selected as one of the scenarios taken into consideration to make the necessary assessments in this regard (see Chapter 7). 2007, pp. 3673 In another study in the Swedish city of Malmӧ, [START_REF] Bӓrring | Canyon geometry, street temperatures and urban heat island in Malmӧ, Sweden[END_REF] concluded that air temperature was not strongly correlated to street canyon geometry as surface temperature was. In Japan however, a relatively strong relationship was found between air temperature and SVF in cities such as Fuchu and Higashimurayama [START_REF] Yamashita | On relationships between heat island and sky view factor in the cities of Tama river basin, Japan[END_REF]. [START_REF] Eliasson | Spatial air temperature variations and urban land use: a statistical approach[END_REF] have demonstrated that both land use parameters and the SVC are important for spatial variations of air temperature within an urban environment. Therefore there are appear to be different views held on whether SVF is related to air temperature but this can be attributed to the range of analytical methods that are used in these aforementioned studies [START_REF] Svensson | Sky view factor analysisimplications for urban air temperature differences[END_REF].

Height to Width Ratio and Street

Orientations. This section discusses some research works conducted on the significance of the impacts of height to width ratio and street orientations on the UHI effects. For example, [START_REF] Ali-Toudert | Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate[END_REF] carried out investigations on the contribution of street design toward the development of a comfortable microclimate for pedestrians during the hot and dry summertime of Ghardaia in Algeria. The main factors investigated in the study comprised: aspect ratio or height (H) to width (W) ratio (H/W), street orientation, overhanging facades, and the use of galleries and rows of trees. As per Oke (1981), the H/W ratio can be used to find the correlation between maximum urban heat island intensity and urban geometry by using the following formula:

ΔT max = 7.54 + 3.97 ln (H/W) ( o C) (Equation 2)

In the aforementioned study therefore, by using a three dimensional model and the physiologically equivalent temperature (PET) to assess thermal comfort level, Ali-Toudert and Mayer were able to determine that street orientation and height-width ratio (H/W) of streets have the most significant impact on the microclimate in urban canyons.

In the case of street orientations in Beirut which lies in the Northern Hemisphere, eastwest orientations of streets will be more significantly affected by the incoming solar rays thus lowering thermal comfort levels as opposed to north-south orientations which provide shade in the morning and in the afternoon on at least one side of the street thus improving thermal comfort levels. Therefore, N-S street orientation leads to less heat stress within the street both in its duration and its intensity but it is important to note that the time of day also plays an important role in this respect. While the effects of street orientations in Beirut is not considered in the numerical analysis for this research due to the selection of the TEB modeling scheme which considers only one direction for all street orientations in the urban canyons, it is important to consider this factor in future research works within the context of devising more sustainable urban planning solutions for the city of Beirut.

As for height to width ratio of streets, in an urban street design that is characterized by wide streets this can result in a stressful thermal environment thus requiring shading strategies. In the case for Beirut, streets are not generally wide (approximately4-6m for local roads and 5-8m for secondary roads), while primary and international roads are generally moderately wider (approximately 8-10m for primary roads and 10-14m for international roads). As for the height of buildings, these are typically not high (average height of approximately 15m) although this trend is fast changing what with the increased demand for more housing, associated with the corresponding rise in urban populations, resulting in taller building constructions (see Chapter 5 for more details on heights of buildings). Therefore, the aspect ratio or H/W ratio is not typically very high for Beirut ranging between 0.5 and 0.8 and therefore effects on UHI are not expected to be significant at present time although there is an increasing probability for this to increase in the near future in Beirut.

Other studies on the effects of urban geometry on the UHI include the works of Fahmy and Sharples (2008) who carried out a research on the thermal behavior of three different types of traditional and modern street canyons with varying densities, orientations, and clusters, in the hot dry semi-arid city of Cairo (see Table 3). They deemed such an investigation essential in establishing an urban planning tool to develop passive cooling policies, which would help reduce thermal stress on internal building conditions, provide ease of movement for people and reduce UHI effects. Only buildings form and green surfaces were simulated so that the effect of different urban pattern forms on the temporal heating of an urban canyon were assessed. Results showed that street orientation and urban geometry, namely street and building compactness, are the most significant parameters for alleviating outdoor thermal comfort levels since as previously mentioned, not choosing optimal street orientations, typically N-S, can retain and trap the incoming solar radiation resulting in a higher heat stress in urban canyons. As for the compactness of each urban pattern case, in terms of SVF, aspect ratios and urban pattern design details, it was found that a medium compact fabric that can produce medium SVF and medium aspect ratios can experience enough wind and solar access to allow for passive cooling and comfortable thermal conditions.

The influence of urban vegetation, building density and height to width ratio on the urban microclimate of the hot and humid city of Taichung in Taiwan were also investigated by [START_REF] Sun | A thermal environment investigation of the urban street canyon in a hot and humid city, Taichung City, Taiwan[END_REF] using air temperature data collected in two streets, which represented differences in street geometry. Vegetation density and building density were also included in the investigation. Results showed a close relationship between street geometry and air temperature at street level. The most comfortable thermal levels were found to occur in the street areas with low building density, low height to width ratio and high vegetation density.

Other urban geometric parameters.

Several other studies have also been conducted to examine the types of urban fabric, urban street designs, and building forms that provide comfortable or optimal thermal levels for city dwellers. For example, [START_REF] Ratti | Building form and environmental performance: archetypes, analysis and an arid climate[END_REF] examined six different building archetypes including courtyards and pavilions with variations on building height, site coverage and total floor space, and discovered that courtyards performed best in terms of built potential and day lighting criteria in arid climates. Within the context of Beirut, housing is typically in the form of apartment buildings (and not single villa type homes) which have an average height of 15m. Due to the limited land availability there are typically no courtyards associated with the apartment buildings but rather limited asphalted parking areas around the perimeter of the buildings and/or sidewalks. To assess the potential impact of courtyards on the UHI phenomenon would therefore not be a realistic scenario for the case of Beirut. In addition, Ratti's research attempts to determine the most suitable building archetype from the perspective of individual buildings while this PhD research attempts to understand the impact of UHI for the whole city scale of Beirut since the objective of this research is to propose mitigating solutions from an urban planning perspective and therefore a larger scale. In their study, [START_REF] Ratti | Building form and environmental performance: archetypes, analysis and an arid climate[END_REF] also stressed on the importance of specifying the climatic zone in which an environmental research on urban form is being considered or undertaken as this may play a key role in identifying most suitable building architectural form for a particular city from an UHI perspective.

The city of Beirut is a coastal city located along the Mediterranean Sea and has in fact been classified as having a coastal climate. Indeed a road map for thermal standards of buildings has already been developed for Beirut in collaboration with the Ministry of Energy and Water (MOEW) but this is still in the process of being approved (see Chapter 5).

Street geometry can also affect the dispersal of anthropogenic pollutants, which in turn can affect urban microclimates. [START_REF] Gromke | Dispersion of traffic exhausts in urban street canyons with tree plantingsexperimental and numerical investigations[END_REF] studied the dispersion of traffic exhaust pollutants in urban street canyons with and without tree plantations.

Although his model proved insufficient for distinguishing between varying canopy densities, the presence of single row of trees hindered airflow in certain areas, leading to increased pollution levels compared to open areas with no trees. Although the impact of trees on increasing pollution levels may seem counterintuitive, another study by [START_REF] Gromke | Interaction of traffic pollutant dispersion with trees in urban street canyons[END_REF] shows the distinction between single-row avenue plantings and larger tree groves emphasizing the latter's significant impact on heat, wind and pollution which act both as a pollution filter and a heat sink [START_REF] Gromke | Interaction of traffic pollutant dispersion with trees in urban street canyons[END_REF]).

There appears to be poor interdisciplinary work carried out between urban designers, architects and urban climatologists [START_REF] Alcoforado | Application of climatic guidelines to urban planning: the example of Lisbon (Portugal)[END_REF][START_REF] Ali-Toudert | Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate[END_REF][START_REF] Grimmond | The international urban energy balance models comparison project: first results from phase I[END_REF][START_REF] Ng | Towards planning and practical understanding of the need for meteorological and climatic information in the design of high density cities: A case based study of Hong Kong[END_REF]. As such, urban temperatures are affected, especially in the summer time, thus impacting the comfort, quality, and health of urban dwellers. In order to improve outdoor thermal comfort levels, especially in hot arid zones (or semi-arid zones as in the case for Beirut), it becomes essential to understand the intricate relationship that exists between climatic conditions and urban form (Fahmy and Sharples, 2008).

In Beirut, information on the potential connection that exists between urban geometry of the city and the urban microclimate is lacking or limited. This is firstly because investigations in this regard have not previously been conducted and in addition because there is insufficient transfer of urban climatic knowledge to urban designers, and planners or policy makers in Beirut. It is not enough to investigate the significant relationship that potentially exists between factors of urban geometry that contribute the most to urban microclimate impacts in Beirut. It is also necessary to improve the communication channels between the concerned disciplines and provide the necessary "evidence" or results to urban planners and decision-makers in the view to find the best mitigation solutions from an urban planning, urban design and even building design perspective (see Chapter 9 for recommendations and solutions in this regard for the Beirut case). [START_REF] Akbari | Peak power and cooling energy savings of shade trees[END_REF] illustrated the relevance of the cooling impact of shading by trees in urban areas in their works on the assessment of peak power and cooling energy savings of shade trees; their results showed substantial cooling energy savings in two houses after shading them with 16 trees. Moreover, Huang, Akbari, and [START_REF] Huang | The wind-shielding and shading effects of trees on residential heating and cooling requirements[END_REF] showed that air temperature in urban areas is reduced by up to 2oC on average both by the direct shading of dark surfaces with dense canopies and by evapotranspiration. In another similar study, [START_REF] Loughner | Roles of urban tree canopy and buildings in urban heat island effects: parameterization and preliminary results[END_REF], showed how the presence of urban trees lowered surface and near-surface air temperatures because of shading and evapotranspiration whereby the addition of trees in the simulations caused maximum daytime and minimum nighttime urban canyon air temperatures to decrease by 4.1 and 2.5K respectively. The removal of trees and vegetation therefore has dire consequences on the ecosystem, the local climate, as well as overall human comfort levels and therefore their role in alleviation of the urban heat island phenomenon is crucial.

In general, investigations carried out on the topic of urban heat islands indicate in one way or another the important role that urban trees, vegetation, and green roofs play, to alleviate uncomfortably high urban thermal conditions of especially hot arid or semiarid dense urban cities [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF][START_REF] Akbari | Potentials of urban heat island mitigation. Prepared for: International Conference on Passive and Low Energy Cooling for the Built Environment[END_REF][START_REF] Shahmohamadi | Mitigating the urban island effect: some points with altering existing city planning[END_REF][START_REF] Oliveira | The cooling effect of green spaces as a contribution to the mitigation of urban heat: A case study in Lisbon[END_REF][START_REF] Rosenfeld | Cool communities: strategies for heat island mitigation and smog reduction[END_REF]. In the study of the most optimal urban street designs on thermal microclimate for example, Ali [START_REF] Ali-Toudert | Numerical study on the effects of aspect ratio and orientation of an urban street canyon on outdoor thermal comfort in hot and dry climate[END_REF] highlighted the importance of having rows of shade trees in urban canyons due to the important role they play in enhancing thermal comfort levels of urban streets.

The leaf area index (LAI) of urban trees, which is the ratio of total upper leaf surface of vegetation divided by the surface area of the land on which the vegetation grows (leaf area / ground surface) is another important parameter that is considered within the context of urban vegetation and their respective impacts on the urban heat island phenomenon [START_REF] Fahmy | LAI based trees selection for mid-latitude urban developments: A microclimatic study in Cairo, Egypt[END_REF]. By definition, LAI can be represented as follows: 3)

LAI = A L /A p (m 2 /m 2 ) (Equation
where A L is the upper leaves area, and A p is the tree ground planting area.

The larger the LAI of an urban tree the larger the shading and cooling provided in an urban canyon. Ideally therefore, urban trees must have a large LAI for maximum shading, latent heat exchange (or evapotranspiration) and pollutant deposition and in addition they must be durable, and must be able to thrive in an urban environment. Trees in fact play a very important role in pollution removal by uptake of gaseous air pollution via leaf stomata (opening or apertures on outer leaf skin layer). Trees are also capable of intercepting airborne particles by either absorbing them into the tree or retaining on the plant surface. Having said this, it is worth noting that some of the intercepted particles are typically released back into the atmosphere, washed off by rain or dropped onto the ground by leaf or twig fall thus not being completely or permanently removed by the urban vegetation. Finally, when choosing the most ideal types of urban trees or vegetation for mitigation of the urban heat island, it is necessary to consider their biogenic volatile organic carbon or VOC emitting properties. Urban trees must not be emitters of VOCs, since this plays a significant role in the formation of one of the most damaging pollutantsground-level ozone (O 3 )which is a major component of smog.

While planting urban trees is an important urban heat island mitigative strategy, a recent study at Yale University showed that high albedo properties of urban surfaces influenced a larger area of the city than the vegetative methods [START_REF] Mackey | Remotely sensing the cooling effects of city scale efforts to reduce urban heat island[END_REF]. Indeed in this study, recent vegetated and reflective surfaces in LANDSAT images of Chicago, a city which has deployed a variety of heat island mitigation measures over the last 15 years, were analyzed. Results accordingly showed that the new reflective surfaces that were implemented in Chicago in 1995 produced a clear impact on the citywide albedo, raising it by 0.016, while citywide NDVI9 increase was found to be at around 0.007.

Moreover, it is worth noting that it is simply not enough to plant any type of urban trees for summertime urban cooling because special consideration should be given to their various properties like LAI, evapotranspiration, VOC emissions, and durability.

As previously mentioned, the LAI of trees plays a significant role in urban microclimatic effects as seen in the works of [START_REF] Fahmy | LAI based trees selection for mid-latitude urban developments: A microclimatic study in Cairo, Egypt[END_REF] where urban trees were selected for urban developments in Cairo depending on their respective LAI based thermal performances. In addition, the evapotranspiration rate of trees should be considered which vary with different tree types. The VOC of trees is also important as it can have significant detrimental effects on air quality via smog formation in cities resulting in human health and respiratory problems. Finally the durability of trees is an important factor when selecting urban trees for urban cooling where certain species of trees cannot adapt to the temperate to semi-arid climatic conditions of the city of Beirut.

By acquiring the input of relevant experts, ensuring an organized institutional framework, and implementing proper sustainable urban planning strategies, it is possible to achieve optimal thermal conditions by planting urban trees in dense cities as seen in the positive modeling results for the cities of Sacramento, Houston and Salt Lake City for example (EPA, 2014) savings in 1997savings in (EPA, 2014)).

Therefore according to the available literature, vegetation planting in urban areas can have significant cooling effects and is therefore an important mitigation strategy for urban heat island in dense cities, but the extent to which this is in fact impacted depends on several factors including LAI, VOC, evapotranspiration, and durability of the trees.

For the case of Beirut, it is important that the existing urban trees and overall vegetation are examined first to determine the extent of their cooling impact on the UHI effect.

Therefore, considering the importance of this scenario that involves increasing urban vegetation fraction to combat UHI in cities, this scenario is also considered for the Beirut case in this research. (see Chapter 7 of this thesis for more details).

Chapter 3: Climate Change, Impacts and Characteristics of Urban Heat Islands and the Energy Balance Equation

In this chapter, the potential relationship that may or may not exist between climate change and urban heat islands is discussed based on the available literature on the topic. Moreover, the various negative effects of urban heat islands is discussed that include mainly impacts to quality of life of city dwellers, modification to thermal comfort levels and even heat-related mortality. This chapter also discusses the various underlying characteristics of the urban heat island that are important to help understand why urban heat islands form in cities. Finally the energy balance equation which explains the transfer of energy to and from the Earth's surfaces giving an understanding as to the fundamental mechanisms by which urban heat island phenomenon functions is discussed in this chapter.

Climate Change and Urban Heat Islands

Within the context of urban heat islands, it is also essential to discuss the widely deliberated topic of climate change. While this research does not attempt to analyze the relationship that may or may not exist between urban warming and global climate change, it does conduct a literature review on the topic to discover expert views, arguments and researches that assess and analyze the relationship between these two phenomena. Indeed the distinction between the two was outlined briefly in the introductory chapter of this thesis, but this section provides further elaboration on the definition of global climatic changes.

As such, upon referring to the Fourth Assessment Report on Climate Change (IPCC, 2007), one of the more widely known reports that documents such information, projections of future changes in climate show that in the next two decades there will be a global warming of about 0.2°C per decade. Even if the concentrations of all greenhouse gases (GHG) 10 and aerosols levels had been kept constant at year 2000, a further warming of about 0.1°C per decade would be expected (IPCC, 2012). Indeed GHSs from human activities are the most significant drivers of observed climate change since the mid-20 th century (EPA, 2014).

The link between these two phenomena is found to be discussed in numerous articles and publications. [START_REF] Dodman | Blaming cities for climate change? An analysis of urban greenhouse gas emissions inventories[END_REF] shows that in most cases per capita emissions from cities are lower than the average for the countries in which they are located (Dodman, 2009, p.6). Moreover, [START_REF] Grimmond | Urbanization and global environmental change: local effects of urban warming[END_REF] claims that the direct contribution of urban warming to global climates is not considerable, arguing that cities and urban areas cover only a small fraction of the earth's surface and that their moisture and thermal effects extend only a few kilometers downwind and that the gases from urban areas are the dominant anthropogenic emissions. She concludes that warmer conditions in many 10 Gases that trap heat in the atmosphere are called greenhouse gases (GHGs). Examples of such gases include carbon dioxide (CO 2 ) which enters the atmosphere through the burning of fossil fuels (coal, natural gas and oil). Methane (CH 4 ) is another GHG which is emitted during the production and transport of coal, natural gas and oil, livestock, and other agricultural practices. Nitrous oxide (N 2 0), another GHG, is emitted during agricultural and industrial activities as well as during combustion of fossil fuels and solid waste.

cities result in greater energy consumption by inhabitants to offset the heat which in turn exacerbate the UHI effect and makes the urban populations more vulnerable to heat waves and other extreme conditions (p.87). Upon application of this argument for the case of Beirut, which is a small city that covers only about 20 km 2 , it can be concluded that urban warming may also have negligible effects on global climate change although impacts on the city-scale are expected to be significant considering the high population density and congestion of the city.

Similarly, Emmanuel and Kruger (2012) argue that since urban areas cover only about 2.8% of the Earth's land area it is unlikely that cities have a direct bearing on global climate change (p.138). However, they do emphasize that cities contribute indirectly to global warming on account of their unquenchable appetite for energy and natural resources and associated waste and pollution. Moreover, when urban population grows the expansion of land covered by cities equally grow on the expense of nonurbanized areas to a point where the direct influence of cities on regional and perhaps global climate becomes more significant [START_REF] Grimmond | Urbanization and global environmental change: local effects of urban warming[END_REF].

On the other hand, some experts in the field have shown that the effects of UHI may be exacerbated in the future due to climate change. , 2011). In this document the sensitivity of human settlements and infrastructure to climate change has been assessed and recommendations have accordingly been given for implementation of adaptation measures. Indeed the report identified a great risk with respect to buildings and structures especially in urban areas by emphasizing that the increase in hot summer days may very well lead to intensification of existing phenomena such as the urban heat island. Some important adaptation measures were accordingly recommended including the adoption of a better design of building envelopes through the use of suitable design techniques and building materials with the aim to reduce cooling demand and render constructions capable of withstanding more extreme climatic conditions (www.moe.gov.lb) although details are not provided as to the means by which these objectives can be achieved. Therefore some important preliminary steps have been taken in this regard although actual implementation is still in the preliminary stages as seen around the city such as a few new constructions in the Ashrafiyeh area which have building envelopes with visibly lighter coloured facades and therefore have less impacts on the surrounding urban microclimate.

Having said this, new building constructions are typically being designed which are much higher than the average building height in Beirut (in general over 10 storeys high or approximately 30m or above), which in itself can be have potentially significant effects on the UHI by minimizing the SVF and trapping more heat in the urban canyons but this is discussed in more detail in Chapter 5 of this thesis.

3.2 Impacts and Characteristics of the Urban Heat Island.

Impacts of the Urban Heat Island.

Human discomfort is one of the main impacts of the UHI phenomenon, leading at times to disease and even mortality. Higher temperatures result in higher energy consumption levels with greater emissions from power plants and consequently increased levels of ozone (O3) resulting in smog formation, and also higher emissions of carbon dioxide (CO2) which both raise urban temperature trends. These higher thermal levels have an adverse effect on human health especially in dense urban areas including general discomfort, heat cramps and exhaustion, respiratory difficulties, non-fatal heat strokes and heat-related mortality (EPA, 2014;Met Office, 2012;[START_REF] Rainham | The role of air pollution in the relationship between a heats stress index and human mortality in Toronto[END_REF]). Moreover, given the global warming forecasts, both frequency and intensity of heat wave episodes will increase and these will accordingly be exacerbated by the UHI effect as witnessed in the excess mortality of 15,000 people in Paris and a death toll in excess of 50,000 people in Europe during the heat wave of summer 2003 (Figure 5 and Figure 6) [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF][START_REF] Chagnon | Impacts and responses to the 1995 heat wave: a call to action[END_REF][START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF].

Therefore, the urban heat island can have significant impacts on human thermal comfort levels, on the quality of life, and can even lead to heat-related mortality. For the case of Beirut, a study was conducted which aimed to show the relationship between heat mortality and increased air temperatures showing a positive correlation between the two factors (El-Zein, Tewtel-Salem & Nehme 2004). However, another study on temperature rises in the Greater Beirut Area (GBA) 11 and their implications on heat-related premature mortality [START_REF] El-Fadel | Climate change and temperature rise in the Greater Beirut Area: implications on heat-related premature mortality[END_REF] found that during the first half of the twentyfirst century, the expected life losses due to high temperatures in hot days are offset by expected life gains due to improved temperatures in cold days, but by the year 2095, the annual average all-cause premature mortality is expected to increase by 3-15%.

Therefore, having said this, there remains a very strong positive relation between rising temperatures and mortality, as emphasized in the existing literature, which is why it is important to investigate the urban parameters that play the most significant role in aggravating the UHI to find immediate mitigating solutions for the case of Beirut especially from an urban planning perspective which can be modified and accordingly improved thus lowering effects on human health and even heat-related mortality as has been successful carried out in many similar dense cities (see Chapter 4 mitigation measures). the urban heat island effect is exacerbated;

 Heat island effect intensifies with increasing development of cities and urban areas;

 In addition to the UHI effect on temperatures in the "urban canopy layer"

(below the tops of buildings and trees), the heat island also affects air temperatures above the trees and buildings of urban areas in what is known as the "urban boundary layer" by a process known as thermal inversion. This is when a warm layer of air covers a layer of cooler air and keeps the cool air from moving.

Table 4 also gives a list of UHI generalizations adapted from the comprehensive review of urban climatic research [START_REF] Arnfield | Two decades of urban climate research: A review of turbulence, exchanges of energy and water, and the urban heat island[END_REF] and correlates each of these characteristics to the Beirut case.

Therefore, these underlying characteristics of the urban heat island help in understanding the mechanisms of this phenomenon and within the context of this thesis, they are especially important upon analyzing the simulations results and devising suitable mitigation strategies for the Beirut case as discussed in more detail in later chapters (see Part IV of this thesis).

The Energy Balance

The UHI phenomenon therefore occurs due to a combination of natural as well as man-made factors, which alter or impact the energy and water cycles of the Earth-Atmosphere systems by which energy and mass are transferred, converted and stored. As such, the earth's energy balance and accordingly its physical climate are modified.

According to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF], the relationship between energy flow and the climate can be explained by the First Law of Thermodynamic where energy can be neither created nor destroyed but only converted from one form to another (Energy Input = Energy Output).

In fact, the physical processes of heat energy transfer occur through radiation, convection, and conduction and play a key role in the earth's energy balance and accordingly its climate and these are discussed in more detail in the sections below.

Radiation characteristics.

All bodies possessing energy or whose temperatures are above absolute zero emit radiation. The total energy emitted by each body can be calculated according to Stefan-Boltzmann's Law [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] that states that the total energy radiated (j) per unit surface area of a black body across all wavelengths per unit time is directly proportional to the fourth power of the black body's thermodynamic temperature as shown in the below equation: j = σT 4 0 where σ is Stefan-Boltzmann's constant (Equation 4)

If the body is not a full radiator, the value of the surface emissivity (ε) will be included j = εσT 4 0 (Equation 5)

The process by which radiation absorption takes place at the earth's surface as well as its reflection back into the atmosphere is fully explained by [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. First, incoming solar beam encounters clouds and other atmospheric constituents like water vapor, salt crystals, dust particles and various gases as it travels through the atmosphere;

Since these constituents have their own set of radiative properties with respect to the short-wave radiation, part of this beam is reflected, part is absorbed and the rest is transmitted to the Earth's surface. In fact, almost 47% of the solar energy input is absorbed at the Earth's surface. This considerable amount of energy is converted from radiation into thermal energy which warms the surface. The portion of the incoming solar radiation that is reflected and scattered gives diffuse short-wave radiation (D), while the portion of the incoming solar radiation that arrives at the Earth's surface, without being absorbed or diffused, is called the direct-beam short-wave radiation (S). The total shortwave radiation received at the earth surface (K↓) is the sum of the diffuse and directbeam short-wave radiation (K↓ = D + S).

At all levels the atmosphere emits long-wave radiation consistent with its temperature (T a ) and emissivity (ε a ). The processes of absorption and re-emission take place on a continuous basis through the atmosphere but quantitatively, they are most important in the lowest layers where the concentrations of water vapour and carbon dioxide are greatest [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. The net portion that emerges from the top of the atmosphere is lost to space; and that which arrives at the Earth's surface is sometimes referred to as "counter-radiation (L↓)" because it counteracts the outgoing long-wave radiation from the surface (L↑).

Convection and conduction.

Another physical process of heat energy transfer occurs through convection which is the energy that is transferred from a solid surface to a fluid and in this case from the earth's surface to the air above it. Convection increases with higher wind speeds, when air becomes more turbulent over rougher surfaces and when there is a significant variation in temperature between the surface and the air [START_REF] Gartland | Heat Islands: Understanding and Mitigating Heat in Urban Areas[END_REF]. If the gain or loss of energy to a body is sensed as a rise or fall in its temperature then this is referred to as sensible heat or "heat energy that is able to be sensed (with a thermometer)". On the other hand, to enable a substance to change from liquid at a given temperature to vapour at the same temperature requires the addition of heat. This heat that is not sensed as a temperature change is called latent heat or the "heat released or absorbed per unit mass by a system in changing phase" [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF].

Convection transports heat to and from the atmosphere in both its sensible and latent forms. When surfaces are warmer than the surrounding air, sensible heat is transferred to the cooler air while the reverse transport occurs when the air is warmer than the surface.

As for latent heat transport, this is tied up with that of water vapour.

Thermal conductivity is another physical process of heat energy transfer and is defined as the energy that is transferred within a substance by the collision of rapidly moving particles. This usually occurs in solids and less so in liquids and gases. It is negligible in atmospheric applications but it is important to the transport of heat beneath the surface. The conduction of heat is dependent on the thermal properties of the substrate in question [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. Therefore, materials with high thermal conductivity are more able to direct heat into their depths. As more heat is stored, the temperature of the material rises [START_REF] Gartland | Heat Islands: Understanding and Mitigating Heat in Urban Areas[END_REF].

Convection and conduction are therefore important physical processes of heat energy transfer and should be considered when analyzing the UHI simulation results for the case of Beirut.

Modification by urban areas.

When an existing landscape is replaced by a building or number or buildings in an urbanization process, modification of the radiative, thermal, moisture and aerodynamic properties of the surrounding environment occurs and the natural solar and hydrologic balances are affected. This is because with the process of urbanization urban construction materials increase, trapping and storing more heat and waterproofing the surface. In addition, the block-like urban geometry causes radiation trapping and air stagnation while man-made activities release excess heat and water in the form of 'waste' which further affects the energy balance. Therefore buildings have a significant impact on the urban microclimate and also on air pollution dispersal but wind and turbulence also play a role on the dispersion of air pollutants. For example, in urban canyons characterized by low buildings, the height to width ratio of streets plays an important role in the exchange between street level, where pollutants are emitted by cars, and above roof-level, so if the streets are narrow, air exchange is restricted (Figure 7a).

On the other hand, urban canyons characterized by wider streets allow for the flushing of these street level pollutants into the air (Figure 7b). Sometimes, where an air-polluting source is placed in the suction zone above the roof of a tall building, the flow of air removal becomes restricted (Figure 7c) but this can be alleviated by constructing a taller stack so that effluent is carried downwind in what is known as the displacement zone. Air pollution dispersal is also stagnated when an-air polluting source is placed near the surface in the eddy of a cavity zone (Figure 7d). Lee eddies are semi-enclosed circulation systems and therefore poor locations for a pollutant source. There is no simple remedy for this latter case except to eliminate the polluting source. There are two sources of energy entering the Earth's surface: 1) man-made or anthropogenic sources including buildings, machinery and people, or 2) net radiation which is defined as the amount of the incoming solar energy that is absorbed, not reflected or emitted away. At any moment in time, anthropogenic heat and net radiation must be convected away by the wind, dissipated by the evaporation of moisture or evapotranspiration from vegetation, or stored in the surface itself [START_REF] Gartland | Heat Islands: Understanding and Mitigating Heat in Urban Areas[END_REF][START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. The energy balance equation is written as follows: 6)

Q* + Q F = Q H + Q E +ΔQ S + ΔQ A (W.m -2 ) (Equation
Where:

-Q* is the net all wave radiation which encompasses four separate radiation processes taking place at the Earth's surface: Net radiation = Incoming solar -Reflected solar + Atmospheric radiation -Surface radiation.

-Q F is anthropogenic heat and represents "man-made' heat generated by buildings, machinery or people Moreover, the energy balance of a building-air volume is given by a relation similar to that for a single building, as written in Equation 6. The term ΔQ S refers to heat storage changes in the ground, the buildings and the air contained within the volume, and Q F refers to heat sources in the city associated with combustion, and which are directly This chapter of the literature review covers the different types of techniques typically adopted to measure the urban heat island phenomenon in dense cities worldwide and discusses the choice of selection for the most suitable technique for the purpose of this research for the Beirut case. In addition, the available literature on the various different modeling schemes available for simulation of the urban heat island is also discussed at length as well as some brief discussions on the choice of selection for the most suitable modeling scheme for this research for Beirut. However more details on the selections made for measurement and modeling techniques for UHI in Beirut including elimination processes can be found in Chapter 6 (Research Methodology) of this research as this chapter covers primarily the literature review content of UHI measurement types and modeling schemes.

-Q H is sensible heat -Q E is latent heat - ΔQ S is

Measuring the Urban Heat Island

The available literature shows that there have been many advances in measuring UHI intensity. Methods used to quantify the effects of urbanization on urban microclimate include: 1) fixed or mobile weather stations, handheld or mounted thermal scanners; 2) aerial orthophotography; and 3) remote sensing thermal images and techniques and these are explained in more detail in the subsequent sections.

Weather stations.

To date, air temperatures records from meteorological stations is the most conventional way used to detect the occurrence and profile of the UHI over cities across the globe. [START_REF] Colacino | Evidence of the urban heat island in Rome by climatological analyses[END_REF][START_REF] Eliasson | Urban nocturnal temperatures, street geometry and land use[END_REF][START_REF] Giannopoulou | On the characteristics of the summer urban heat island in Athens, Greece[END_REF][START_REF] Katsoulis | Indications of the urban heat island in Athens, Greece[END_REF][START_REF] Vez | A study of the urban heat island of Granada[END_REF]. Data are typically acquired from existing weather stations or from micro-weather stations setup purposefully at specific locations with different land use and land cover such as: coastline, dense inner city, commercial or office area, residential area, etc. To that end, day and night time minimum and maximum temperature records are monitored and compared for specific times of the day over a determined period (day, month or season). Records are then compared to historical temperature records and trends to identify unusual climatic pattern and any associated impact on the UHI.

For example, [START_REF] Giannopoulou | On the characteristics of the summer urban heat island in Athens, Greece[END_REF] monitored temperature data from 25 fixed meteorological stations during the summer season of year 2009 in the major Athens area in order to study the characteristics of the UHI phenomenon. The greater area of Athens was divided into 5 geographical parts each being characterized by its own specific urban morphology and land uses. Results showed that each of these 5 areas had different temperature conditions; the higher air temperatures were found in the industrial western part of the city and also the central dense urbanized area, while the lower temperature values were presented at the northern and eastern parts characterized by their higher percentage of green areas and the absence of industrial zone and identified UHI intensity close to 5 o C. In general, it was found that this method of using fixed weather stations to study the UHI in Athens was successful in that it helped to draw important conclusions as follows:

1. the development of high summer air temperatures is mainly as a result of the presence of high mountains (over 1000m a.s.l.) surrounding the Athens area; and 2. the urban heat island during the night period was observed mainly in the industrial western part of the city.

Another example where weather stations were used to study the UHI can be seen in the works of [START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] for the city of Salamanca in Spain. In these works, the experts: 1) investigated the temporal evolution of UHI intensity for the period 1996 to 1998; and 2) compared temperature records between an urban area and a nearby rural area. To this purpose, the spatial distribution of the UHI was analyzed by using the transect selection method for two measuring transects in the city. For the measurement of temperature along these two selected measuring transects, a digital thermometer with a resolution of 0.1 o C was used. In general the results indicated that the Tormes River in relation to the city of Salamanca played a significant role in determining the city's thermal characteristics. In addition, results showed that the UHI was more intense under conditions of atmospheric stability as compared to conditions of atmospheric instability.

In the city of Granada in Spain, [START_REF] Vez | A study of the urban heat island of Granada[END_REF] studied the effects of the UHI by investigating weather station records. Here however, it is worth noting that reference was made to the historical temperature evolution of the last century for only one meteorological station, namely Cartuja station, and analysis was carried out by application of statistical methods. However, comparisons between both rural and urban temperature records were also carried out but over a much smaller time-scale, probably due to lack of data for previous years. For the rural temperature records a military airdrome site uninfluenced by urbanization was selected. Using the time series of temperature differences, daily maximum and minimum temperature records were obtained for annual and seasonal periods with results showing maximum differences occurring only during the winter months. It is important to note that the results also showed that population growth was very closely related to the trends in temperature records.

On the island of Taiwan, air temperature data were also collected for the purpose of analyzing the thermal environment in two urban street canyons in the hot and humid city of Taichung (Sun, Kato, Sung, Lin, Wang, and Ou, 2009). Again, this method of study helped to find important correlations between the urban fabric, including building density, street height to width ration and vegetation, and the urban heat island phenomenon.

Therefore, as can be seen in the available literature, the application of this method of analysis for urban atmospheric temperatures is quite common in cities worldwide

although it has proven to be time-consuming, is weather-dependent, can be quite costly depending on the choice of instruments, and requires good coordination amongst all involved parties to reduce the margin of error to the extent possible.

For the case of Beirut, there are several weathering stations that exist which are associated either with academic institutions, like for example the station at the American University of Beirut (AUB) 12 or governmental agencies, like stations that are operated by the Lebanese Institute for Agricultural Research (LARI) 13 and that are spread out across 12 The American University of Beirut (AUB) is a private, secular, and independent university in Beirut, founded in 1862. A weather station was installed for the university soon after it was established up until 1975, what marked the start of the Civil War in Lebanon. A new station was set up after the end of the Civil War although the old station still remains and is referred to the "AUB Old Observatory". As such, AUB currently participates in independent environmental related projects that require basic weather data measurements e.g., Beirut Air Quality project in collaboration with Beirut Municipality, AUB and the University of Saint Joseph (USJ), another private French academic institute. These institutions typically provide data only to their students or upon official request from governmental authorities and are associated with fees. 13 LARI is a governmental organization under the Minister of Agricultural supervision. The institute conducts applied and basic scientific research for the development and advancement of the agricultural sector in Lebanon and has accordingly been measuring weather data since 2009 at stations spread out across the country.

the country including Beirut, or like the station at Rafik Hariri International Airport 14 .

However, there is no available information, documentation or publication to indicate that these aforementioned sources have conducted any works on the UHI phenomenon in Beirut. Having said this, reference is made to these aforementioned stations within the context of this research for Beirut, to collect historical climatic records and to accordingly conduct numerical analysis of historical weather patterns, namely maximum and minimum temperature trends (see Chapter 6 of this thesis for more details).

High resolution aerial ortho-photos. High-resolution aerial ortho-

photography is also a commonly used method in the study of the urban heat island phenomenon. As the term suggests, aerial photographs are images that are taken of the ground from an elevated position that are of high quality, sharp and finely detailed and among other purposes are very useful for studying the effects of the urban heat island.

In their study of the urban heat island phenomenon, Akbari, Shea-Rose and Taha (2003) used high-resolution aerial colour photography to characterize the area fraction of various surface types and vegetation fraction in the city of Sacramento. They stressed the importance of carrying out this characterization when estimating the impact of various urban surfaces (roofs and pavements) on the UHI. As such, they examined five land use types including: 1) downtown and city center; 2) industrial; 3) offices; 4) commercial;

and, 5) residential. Their results showed the urban surface area fractions of these five different land use areas, which could essentially be very useful when comparing UHI effects in these areas of Sacramento city.

In another similar study, [START_REF] Akbari | Urban surfaces and heat island mitigation potentials[END_REF] investigated urban surface type distributions and urban-fabric makeup using aerial colour orthophotography for four 14 Weather records began in the year 1932 at the Rafik Hariri International Airport metropolitan areas in the US, including Chicago, IL, Houston, TX, Sacramento, CA, and Salt Lake City, UT. The major land use types examined included: commercial, residential, industrial, educational and transportation. Each aerial orthophoto was visually inspected using ERDAS/Imagine software (ERDAS, [Earth Resources Data Analysis System, 1997) to identify qualitatively all surface-types and land-covers that can be seen at the resolution of the data. In this study, Akbari and Rose found that it is possible to characterize the fabric of a region of interest accurately and cost-effectively using aerial orthophotography further stating that between, 10 to 50 km 2 of aerial photography would suffice for reasonably good characterization of the fabric. As a result of these investigations, Akbari and Rose were able to conclude that there is large potential for additional urban vegetation as well as increasing albedo for these four metropolitan areas.

In their works on the modeling of the urban environmental quality in Hong Kong, [START_REF] Nichol | Modeling urban environmental quality in a tropical city[END_REF] apply satellite-based sensing systems to depict parameters of environmental quality over large areas. In their methodology, they use colour orthophotography to give specific and clearer details of the area under study. By applying this method, they are able to accurately identify the various characteristics of the area being studied determining that it is a small park within a densely built area of Mongkok district in Hong Kong.

Aerial orthophotos therefore play an important role in the investigation and indepth study of urban heat islands and environmental quality. However, according to the existing literature, aerial orthophotos are used primarily to determine the fraction of

Thermal remote sensing.

With the advent of high-resolution earthmonitoring satellites, these last two decades or so have witnessed a significant increase in the application of thermal remote sensing to study urban effects on meteorology, climate, and urban heat islands, as opposed to the more traditional in-situ measurements that are carried out in isolated locations. Thermal remote sensing is a method used to study urban surface temperatures by observing surface temperature which varies in response to the surface energy balance [START_REF] Voogt | Thermal remote sensing of urban climates[END_REF]. It is that branch of remote sensing that deals with the acquisition, processing and interpretation of data acquired primarily in the thermal infrared (TIR) region of the electromagnetic (EM) spectrum where the radiations 'emitted' from the surface of the target are measured as opposed to optical remote sensing where radiations 'reflected'' by the target under consideration are measured [START_REF] Gupta | Remote Sensing Geology[END_REF]. Satellite images have therefore made it possible to study the effects of the UHI both remotely and on continental or global scales [START_REF] Streutker | A remote sensing study of the urban heat island of Houston, Texas[END_REF] and are typically used to study land surface temperatures [START_REF] Parlow | Remotely sensed heat fluxes of urban areas[END_REF][START_REF] Qin | Progress in the remote sensing of land surface temperature and ground emissivity using NOAA-AVHRR data[END_REF].

There do, however, appear to be some limitations in the application of thermal remote sensing images to study urban heat islands. For example, thermal remote sensing is not able to capture the thermal properties of tall vertical surfaces and facades such as trees and buildings [START_REF] Streutker | A remote sensing study of the urban heat island of Houston, Texas[END_REF][START_REF] Voogt | Thermal remote sensing of urban climates[END_REF]. Therefore it is limited in its ability to identify the features that dominate the landscapes of urban areas [START_REF] Akbari | Urban surfaces and heat island mitigation potentials[END_REF].

According to [START_REF] Voogt | Thermal remote sensing of urban climates[END_REF], while some progress has been made in the application of thermal remote sensing of urban areas, it has in fact been "slow to advance beyond qualitative description of thermal patterns and simple correlations". Akbari and Shea-Rose ( 2008) also find that "while advances in techniques in the fusion of GIS data and remote sensing among others are promising, they have yet to characterize disaggregated urban features in a manner that is practical and accurate enough for applied city planning". [START_REF] Voogt | Thermal remote sensing of urban climates[END_REF] suggest applying the advances made in the remote sensing measurements of vegetative surfaces to urban areas, while [START_REF] Akbari | Analyzing the land cover of an urban environment using high-resolution orthophotos[END_REF] find that when comparing the various available data resources (including thermal remote sensing images), high resolution colour digital orthophotos offer the best means for obtaining accurate estimates of urban fabric to accordingly study the urban heat island phenomenon.

In his study of the urban heat island in the city of Houston Texas, [START_REF] Streutker | A remote sensing study of the urban heat island of Houston, Texas[END_REF] also identifies some limitations of remotely sensed data used in making temperature determinations: "remotely sensed derived temperatures are surfaces temperatures of the emitting materials, and not air temperatures, as in situ measurements often are". As such, this can cause surface temperatures to exhibit a much greater spatial variation than the concurrent air temperatures [START_REF] Streutker | A remote sensing study of the urban heat island of Houston, Texas[END_REF]. This shortcoming is further emphasized by [START_REF] Arnfield | Two decades of urban climate research: A review of turbulence, exchanges of energy and water, and the urban heat island[END_REF] who explains that remotely sensed UHIs are usually stronger and exhibit greatest spatial variability by day, the opposite to air temperature UHIs. As further explained by [START_REF] Roth | Satellite-derived urban heat islands from three coastal cities and the utilization of such data in urban climatology[END_REF], the reason for this is because remote sensing tends to oversample roofs, treetops, and roads and open horizontal areas while it neglects areas below tree crowns. Having said this, the application of thermal remote sensing to study

UHIs is fast spreading with continual suggestions and applications for improvements. For example, in their study of the assessment of the urban heat island effect for 37 dense cities across the U.S.A. and their respective nearby rural regions, [START_REF] Gallo | The use of NOAA AVHRR data for assessment of the urban heat island effect[END_REF] used data from the NOAA (National Oceanic Atmospheric Administration) Advanced Very High Resolution Radiometer (AVHRR)

and derived a vegetation index and radiative surface temperature for these urban-rural areas. By comparing urban-rural differences in computed versus observed situations in minimum air temperatures, Gallo et al. were able to determine that the difference in the surface properties between the two environments is the main reason for the resulting differences in urban and rural minimum temperatures [START_REF] Gallo | The use of NOAA AVHRR data for assessment of the urban heat island effect[END_REF]. The use of the remotely sensed data was therefore very suitable for these large areas under study as opposed to the application of in-situ measurements.

From 1998 to 1999, [START_REF] Streutker | A remote sensing study of the urban heat island of Houston, Texas[END_REF] studied the urban heat island effects of the highly populous city of Houston, which covers a large geographic area. His study was based on temperature maps from AVHRR data. In the application of this approach to study UHI, and after carrying out the radiometric correction, cloud and water rejection, rural subtraction, and UHI characterization as necessary for the interpolation of the required temperature data, Streutker concluded that the application of this type methodology showed that satellite radiance data can be used to characterize both the magnitude and spatial extent of an urban heat island with suggestions to carry out future studies for more prolonged periods of time as well as .over several urban areas in a given region.

Recently, in Beijing, Yang, Gong, Zhou, Huang, and Wang (2010) evaluated the suitability of using thermal infrared (TIR) data from satellite imagery for detecting UHIs.

This was validated against a previous study carried out in Beijing. The study essentially demonstrated that the application of thermal remote sensing is successful in studying surface UHIs. Others have applied thermal remote sensing in combination with another methodology (hybrid methodology) to study UHIs, such as Geographic Information System (GIS), as done for the Kawasaki, Japan case [START_REF] Iino | Development of a method to predict the heat island potential using remote sensing and GIS data[END_REF]. Here it was found that it was possible to construct urban thermal images accordingly giving a clear idea as to where energy problems potentially occur and how this information could be employed in proper urban development planning.

In general, the application of thermal remote sensing methods to study UHI (in combination, or not, with GIS or other similar tools) appears to be quite popular, according to the authors mentioned, who generally compare the results of their studies to other case studies representing temperature records of cities. Having said this there still seems to be room for improvement for application of this type methodology for measurement of UHI. This choice for UHI measurement was not selected for the purpose of this research however mainly since the available thermal remote sensing images are limited for Beirut city or are not very clear for easy extrapolation of surface thermal data (see Chapter 6 for more details on choice of selection for measurement technique of UHI).

Summary.

Based on the literature review on the different measurement types for UHI measurements in cities it is found that all approaches equally have advantages as well as limitations as outlined in Table 5. This table below helps in the selection process of this research for the most feasible approach for the Beirut case although as a preliminary assessment it is found that all these measurements types may not be suitable. Rather, the collection of weather data from existing weather stations in Beirut may potentially be the most feasible approach thus avoiding all the limitations associated with the outlined measurement types. Beijing, China, 37 dense cities across the U.S.A [START_REF] Gallo | The use of NOAA AVHRR data for assessment of the urban heat island effect[END_REF] Houston, Texas

Modeling the Urban Heat Island

Modeling of urban heat islands is useful to both help understand how the UHI works and to estimate how effective application of different mitigation measures types can be. As such, after reviewing the existing literature on the topic, it is important to select the most suitable modeling scheme for the Beirut case in order to conduct simulations across the city that could potentially provide feasible solutions for mitigation of the UHI from an urban planning and design perspective.

Numerous models have been developed which vary widely with regard to both their physical basis and spatial/temporal resolution [START_REF] Emmanuel | Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA[END_REF]. The available literature on this topic shows many comparative studies that assess and evaluate urban land surface schemes that have been developed to model the distinct features of the urban surface and the associated energy exchange processes. While most of the applied models show relatively successful simulation results, each is specific to the scale it which it can be used. Therefore, in this section of the literature review, out of the numerous models developed worldwide to study the effects of UHI [START_REF] Grimmond | The international urban energy balance models comparison project: first results from phase I[END_REF][START_REF] Grimmond | Initial results from Phase 2 of the international urban energy balance model comparison[END_REF], the modeling schemes most commonly mentioned in the available literature are discussed based on the scale at which they are used i.e., whether micro-scale, local-scale, meso-scale or macroscale. As such, for micro-scale and localscale modeling schemes, the NARPS-LUMP, SM2-U, ENVI-met and SOLENE models are discussed and compared. For meso-scale models, the Town Energy Balance (TEB) model and the Finite Volume Model (FVM) are discussed and compared. As previously mentioned at the beginning of this chapter, while the choice of selection of the most suitable modeling scheme of UHI in Beirut is briefly discussed here, more details for the elimination and respective selection process can be found in Part IV of this thesis.

Micro-scale and local scale modeling schemes.

In this section, details on four modeling schemes that are used typically for UHI simulations at the micro-scale or local scale i.e., building level or neighborhood level, are discussed, which include NARP-LUMPS, SM2-U, ENVI-met, and SOLENE.

NARP-LUMPS. The NARP-LUMPS model (Net All-Wave Radiation

Parameterization / Local-scale Urban Meteorological Pre-processing Scheme) which was developed by [START_REF] Grimmond | Turbulent heat fluxes in urban areas: Observations and a local-scale urban meteorological parameterization scheme (LUMPS)[END_REF], is an empirical model that is used typically for small-scale studies. It is used to assess the energy balance of a city but it simplifies the energy balance equation without incorporating the anthropogenic heat flux produced by combustion processes, metabolism and waste heat (QF) and by ignoring the advective heat flow (QA) and thus considers the following formula: 7)

Q* = Q H + Q E +ΔQ S (W.m -2 ) (Equation
Where:

-Q* is the net all wave radiation According to [START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF], NARP-LUMPS is adequate if the observational field data are sufficient and well understood. The main asset of this model is its simplicity since it needs very few inputs and its computation is very efficient although its main weakness is that it is only valid in the range of conditions observed in the field [START_REF] Hidalgo | Advances in urban climate modeling[END_REF]. Indeed in their paper introducing this empirical model, [START_REF] Grimmond | Turbulent heat fluxes in urban areas: Observations and a local-scale urban meteorological parameterization scheme (LUMPS)[END_REF] acknowledge that their model is very simplistic and would potentially need additional input requirements with special consideration of the effects of wind and anthropogenic heat. In addition, they emphasize 100 that LUMPS is unlikely to perform well in areas of greater spatial variability of land cover and/or morphology such as at the urban-rural edge, near coasts or in complex terrain.

-Q H is sensible heat -Q E is latent heat - ΔQ S is
Therefore, the available literature shows that NARP-LUMPS is a simple empirical model that is used mainly for micro-scale studies of the UHI. This model is therefore not feasible for the purpose of this research which aims to study the UHI effect at the mesoscale level, for the entire city of Beirut, in the view to find solutions from an urban planning perspective.

SM2-U.

The SM2-U (Soil Model for Sub-Mesoscale Urban) model, developed by the Ecole Centrale de Nantes, calculates heat flux at the canopy-atmosphere interface across a district. It can be coupled with SUBMESO, which is a non-hydrostatic model also developed by the Ecole Centrale de Nantes.SUBMESO simulates atmospheric flows with a resolution up to a few meters to several kilometers [START_REF] Mestayer | Satellites pinpoint drivers of urban heat islands in the northeast[END_REF].

SM2-U is a single canopy layer models built on a physical basis from the Integration with Soil Biosphere and Atmosphere (ISBA) rural soil model (Noilan and Orderly, 1989) by including urban surfaces to evaluate the heat and humidity fluxes at the urban canopyatmosphere interface and provides the lower boundary condition of the computational domain in simulations of the urban boundary layer [START_REF] Mestayer | Satellites pinpoint drivers of urban heat islands in the northeast[END_REF]. SM2-U has the advantage of being a unique model covering both rural and urban soils. Furthermore, the physical processes inside the urban canopy, such as heat exchanges, heat storage, radiative trapping, water interception or surface water runoff, are integrated in a simply way. In the SM2-U model therefore, the surface dynamic influence is represented through roughness lengths and displacement heights.

The horizontal exchanges inside the urban canopy are not considered except radiation reflections and water runoff from saturated surfaces the wind advection between urban surfaces is also not considered.

According to [START_REF] Mestayer | Satellites pinpoint drivers of urban heat islands in the northeast[END_REF], SM2-U considers eight types of surfaces including: bare soil without vegetation; bare soil located between sparse vegetation elements; vegetation over bare soil; vegetation over paved surfaces (e.g., trees on the road side), paved surfaces located between the sparse vegetation elements, paved surfaces located under the vegetation, building roofs, and water surfaces, respectively denoted as bare, nat, vegn, vega, pav, cova, roof and wat as illustrated in Figure 10. Mestayer, et al., 2004, pp.3 In each computational cell, each surface type is characterized by its area density fi, the index I corresponding to one of the 8 surface types. Three soil layers are considered: a surface layer for the natural surfaces, allowing evaluation of the evaporation fluxes from the bare soils; a root zone layer representing the influences area of the vegetation roots; and a deep soil layer used as a water reservoir which provides water to above soil layer by diffusion in dry periods [START_REF] Mestayer | Satellites pinpoint drivers of urban heat islands in the northeast[END_REF]. In each cell, the model determines 1) for each type surface its surface temperature, specific humidity and energy fluxes, 2) the deep soil temperature, 3) the mean potential surface temperature and the mean energy flux, and 4) the water content of each soil layer and the water amount intercepted by roofs, vegetation and paved surfaces. SM2-U does not evaluate the energy budget of building walls to avoid introducing a questionable parameterization of the wind velocity inside the canopy [START_REF] Mestayer | Satellites pinpoint drivers of urban heat islands in the northeast[END_REF]. [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF] describes the SM2-U model as a "simple" model which can be used to illustrate the influence of alternative mitigation techniques on the urban microclimate. In his paper, [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF] uses the SM2-U modeling scheme to assess the impact of two alternative rainwater management mitigation techniques and is accordingly able to provide feasible recommendations based on the simulation results of SM2-U. Hence he considers this to be a reliable simulation tool although he does recommend the need for the model to consider additional urban morphology parameters and material properties for improvement of this particular modeling scheme. Therefore, according to the available literature, SM2-U is a fairly simple model and has been proven to be useful in devising feasible recommendations for mitigation tools. However, since SM2-U model is used typically for neighborhood scale studies, it is not found to be feasible for the purpose of this research which aims to study the effect of UHI at the cityscale.

ENVI-met. ENVI-met (Environmental Meteorology) was developed

within the Research Group of Climatology (RGC), Department of Geography at the University of Buchum in Germany by Michael Bruse [START_REF] Bruse | The influences of local environmental design on microclimate[END_REF]. ENVI-met is a threedimensional micro-climate model designed to simulate the surface-plant-air interactions in urban environments with a typical resolution of 0.5 to 10m in space and 10 seconds in time. Therefore, ENVI-met is applied typically for micro-scale projects at the building scale or neighborhood levels for example and is not used for large-scale studies (www.envi-met.com). [START_REF] Huttner | Numerical modeling of the urban climatea preview on ENVI-met 4.0[END_REF]. Figure 11 shows the basic data structure of ENVI-met. Figure 12 shows a typical output of ENVI-met for a linear park in Phoenix, Arizona, where the darker colours (dark blue in this case) typically reflect cooler surfaces [START_REF] Ozkeresteci | Use and evaluation of the ENVI-met model for environmental design and planning: an experiment on linear parks[END_REF]. In this aforementioned study, these linear parks were investigated in ENVI-met first to evaluate the practical applications of the model and second, to assist Phoenix metropolitan area planners in advancing their open space and park planning strategies. Numerous studies for analysis of UHI have been conducted using ENVI-met. Ali-Toudert and Mayer ( 2006) applied ENVI-met to study the effects of aspect ratio and solar radiation toward the development of a comfortable microclimate at street level for pedestrians in the town of Ghardaia in Algeria [START_REF] Bruse | ENVI-met 3.0: updated model overview[END_REF]. Their argument for using this specific modeling scheme was that it requires few input data parameters to calculate all important meteorological factors; it has the ability to reproduce major processes in the atmosphere that affect the microclimate, and it has high spatial and temporal resolution enabling a fine understanding of the microclimate at street level. According to [START_REF] Emmanuel | Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA[END_REF] however, this modeling scheme does have some major shortcomings since buildings which are modeled as blocks have no thermal mass and have constant indoor temperatures and the albedo for walls and roofs are the same for all buildings. Having said this, ENVI-met modeling scheme was used also in the works of [START_REF] Emmanuel | Urban heat islands in humid and arid climates: role of urban form and thermal properties in Colombo, Sri Lanka and Phoenix, USA[END_REF] where the effects of UHI mitigation options were analyzed within the heavily built up street canyons of the city of Pettah in Colombo and the central business district of Phoenix.

ENVI-met is

Yu and Hien ( 2006) also used the ENVI-met model to explore the patterns of energy consumption of a typical commercial building near to a nature park in Singapore and different thermal conditions of an area with and without a neighborhood park. Yu and Hien accordingly found that the ENVI-met simulations supported the data generated from field measurements which indicated that the park has significant cooling effects on the surroundings both during the day and night. Also, the simulations results on ENVImet illustrated the truth that the loss of greenery may cause bad thermal conditions not only in the original park area but also in the surroundings especially when greenery is replaced by buildings and hard surfaces.

Therefore according to the available literature it is found that the use of ENVImet model is widespread in UHI associated works where results appear to be acceptable in all cases but the only drawback within the context of this research is that it is used typically for micro-scale or local-scale studies and is therefore not feasible for the purpose of this research which aims to find mitigation solutions for UHI at the city of scale of Beirut as opposed to neighborhoods or individual buildings. According to [START_REF] Groleau | Simulation of the radiative behaviour of an urban quarter of Marseille with the Solene model[END_REF], SOLENE is based on a 3D modeling scheme and takes into account the interactions between urban form and its environmental dimensions including the climate by correlating geometric data of urban form (such as layout, density, street orientations, type of building…) with the physical properties of the built environment (roughness length, sky view factor, solar radiation).

Solene

The application of SOLENE is varied and can be used for example to assess the temperature of surface walls and outdoor comfort levels, air temperatures 1.5m above ground and surface temperatures. Two factors not taken into account by SOLENE include anthropogenic heat and the latent heat flux [START_REF] Ringenbach | Bilan radiative et flux de chaleur en climatologie urbaine: mesures, modélisation et validation sur Strasbourg[END_REF]. Figure 13 shows the outputs of SOLENE with simulations for surfaces temperatures and solar flux calculated at building surfaces, trees and on the ground. This therefore assists in drawing urban designs and building designs that have low or nominal impacts on the microclimate with respect and is therefore a useful modeling tool for micro-scale projects. In a study conducted by [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF], the UHI phenomenon and its effects on energy demand at the building scale were assessed. SOLENE modeling scheme was selected whereby the model's capabilities, in a coupled approach, were investigated. In this study therefore, SOLENE was used to investigate the impact of trees and natural soil against the impact of the mineral environment on buildings' energy demand in the city of Lyon in France. It was accordingly found that the coupling procedures for SOLENE had a weak but non-negligible impact on the energy consumption assessment of buildings. This is an important factor when designing buildings as energy demand and associated gas emissions from air conditioning use and heating use can potentially contribute significantly to the heat island effect. Therefore, SOLENE has been used in mainly the architectural domain to design buildings with least impact on the microclimate but it is used for micro-scale or local scale studies and is therefore not feasible for the purpose of this research for Beirut.

Therefore, all four micro-scale and local-scale modeling schemes discussed above are deemed unsuitable for the purpose of this research which aims to analyze UHI effects at the city-scale of Beirut in order to propose recommendations and mitigation strategies from an urban planning point of view. Having said this more details regarding the selection of most suitable modeling scheme for the Beirut case can be found in Chapter 6 of this thesis.

Mescoscale modeling schemes.

In this section of the literature review, two models which are typically used to conduct simulations at the mescoscale or city-scale are discussed namely the Town Energy Balance (TEB) and the Finite Volume Module (FVM). The mechanisms by which these two modeling schemes function are therefore discussed and compared in the view to determine the most suitable modeling scheme for UHI simulations for the Beirut case.

Town Energy Balance (TEB).

Due to the extensive literature on the Town Energy Balance (TEB), this section is divided into the following sections: 1) the first section gives an introduction to TEB and the various hypothesis the modeling scheme is built upon; 2) the second section discusses the mechanism by which this scheme fundamentally functions; 3) the third section gives an outline of the vegetation (veg) scheme which was recently integrated into TEB and discusses the associated advantages of this new approach, and; 4) the fourth and last section discusses the new Building Energy Model (BEM) which was also recently integrated into the TEB scheme and gives an account of the various advantages associated with this new option for this model.

Introduction to TEB

The Town Energy Balance (TEB) model was developed by [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] at Centre National De Recherches Météorologiques (CNRM) at Météo-France in Toulouse,

France and is used to parameterize town-atmosphere dynamic and thermodynamic interactions. It is included in the SURFEX land-surface modeling system (www.cnrm.meteo.fr/surfex), which means "surface externalisée" and is a code that represents the energy exchange processes that occur between the atmosphere and the urban surfaces. SURFEX is "externalized" which means that the code can be used inside TEB is built following the canyon approach and is applicable for mesoscale atmospheric models (a grid mesh larger than a few hundred meters). It simulates the turbulent fluxes into the atmosphere at the surface of a mesoscale atmospheric model by treating the urban area as a series of urban canyons whereby each grid mesh is considered to be comprised of a single road bordered by facing buildings. It should be noted that TEB requires spatial averaging of town characteristics as well as its effect on the atmosphere. As such, individual shapes of each building are not taken into account, and in this way it is based on the canyon geometry approach. Therefore TEB incorporates canyon geometry with three typical surfacesroof, road, and wallin order to reproduce the effects produced by buildings and is a single-layer urban canopy model where there is direct interaction between one atmospheric layer above the uppermost roof layer.

TEB is "forced" with atmospheric data and radiation recorded above roof level and incorporates detailed representation of the urban surface (canyon geometry) to simulate energy balances for each of the three surfaces including roofs, roads and walls.

"Force" is the terminology used in SURFEX to describe the climatic conditions that are prominent in the city, including for example temperature, and wind, and that are accordingly used to carry out the simulations. TEB therefore considers the following hypotheses for city representation:

 The buildings have the same height and width (in the model mesh), with the roof level at the surface of the atmospheric model;

 Buildings are located along identical roads, the length of which is considered far greater than their width; the space contained between two facing buildings is defined as a canyon;

 Any road orientation is possible and all exist with the same probability. This hypothesis allows the computation of averaged forcing for road and wall surfaces.

These hypotheses therefore allow for the development of a relatively simple scheme but which still allow for most of the physical effects associated with the urban energy balance to be reproduced. The advantage of such a simple scheme for the Beirut case for example is that since the available data on urban form is limited, the dominating urban characteristics (including urban form and material composition) for roads, rooftops and wall surfaces can be considered in the numerical analysis process. This also includes dominating building height and street orientations. However, this can cause a small margin of error in the analysis since if there are for example a total of 20 buildings within a grid mesh for Beirut and 7 out of these 20 buildings are taller than the rest, their respective impact on UHI will not be precisely considered in the simulations. In this case the trend in urban form is taken into consideration in TEB as opposed to individual building specifications.

TEB Mechanism

Fundamental to the mechanism by which TEB functions therefore is the concept of the urban surface energy balance (see Figure 15) as defined by Oke (1987) (see Equation 6 in Chapter 3), which is applied in TEB to an entire urban area. The TEB scheme therefore computes the surface energy budget for each of the roofs, roads and walls surfaces treating each grid mesh as an urban canyon comprised of a street, walls and roofs [START_REF] Lemonsu | Simulation of a summer urban breeze over Paris[END_REF][START_REF] Lemonsu | Modeling of the surface energy balance of the core of an old Mediterranean city: Marseille[END_REF][START_REF] Masson | Evaluation of the Town Energy Balance (TEB) scheme with direct measurements from dry districts in two cities[END_REF]. In Figure 15 it is seen that the roofs, roads and walls are represented in terms of four layers as presented by subscripts R, r, and w for roofs, roads and walls respectively and by this TEB takes into account the process of heat conduction into these artificial materials.

Regarding surface temperatures, the model does not use one urban surface temperature but rather three surface temperatures representative of roofs, roads and walls (T R , T r , T w ) hence it uses a complex surface consisting of multiple explicit energy budgets. In this figure it is also seen that the model is forced with a temperature (T a ), humidity (q a ), and wind speed (U a ) measured in the inertial sub-layer. The rooftop level is the surface of the atmospheric model so the TEB computed sensible heat flux (Q H ) for the urban canopy is assigned at the base of the first atmospheric grid box. The aerodynamic resistances are also represented by the thick lines in Figure 15 and include the aerodynamic road resistance (R r ), aerodynamic roof resistance (R R ), and aerodynamic wall resistance (R w ).

Therefore based on the surface energy balance of [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] the surface energy budget of each of the roof, road and wall surfaces in a grid mesh representing an urban canyon are computed.

Thus TEB takes into account the processes that influence mainly the urbanatmosphere energy exchanges in which the urban or town part is defined by roads, roofs and wall surfaces. It carries out fast numerical simulations for large urban areas and does not require reproduction of each building with the exact specifications of either geometry or orientations. The city is divided into grid meshes of identical dimensions each defined by three geometric parameters including dominating width and height of the buildings and width of the streets that are kept constant within each grid box of the model with identical street orientations. The approach is relatively simple but still allows most of the physical effects associated with urban energy balance to be reproduced, including longwave and shortwave radiative trapping, the momentum flux, the turbulent sensible and latent heat fluxes, and heat storage uptake and release. Anthropogenic heat fluxes due to traffic and industry are also considered in TEB but it is worth noting that anthropogenic heat flux is not prescribed in the analyses since the objective of this research is make recommendations for the urban planning of the city and not anthropogenic heat emissions.

TEB-Veg

The TEB model was recently improved to include vegetation directly inside the canyon. According to Lemonsu, Masson, Shashua-Bar, Erell, and Perlmutter (2012), this new version of TEB with integrated vegetation, including ground-based vegetation inside the canyons such as private gardens and backyards as well as trees inside the streets and green roofs and walls, performs better than if vegetation is treated outside the canyon.

This is mainly because it allows for shadowing of grass by buildings; it provides a better representation of urban canopy form and gives a more accurate simulation of the canyon air microclimate. Before vegetation was integrated directly into TEB and in the presence of vegetation in the canyons, SURFEX was run with TEB and ISBA models. This latter design however was found to present some problems since vegetation was considered an open area not subject to the shadow effect of buildings and to radiation trapping within the canyon. In addition, the canyons were assumed to be narrower than they were in reality as the vegetation was placed outside the canyon hence unrealistic geometric parameters were prescribed for TEB (for more detailed discussions refer to [START_REF] Lemonsu | Inclusion of vegetation in the Town Energy Balance model for modeling urban green areas[END_REF]. Figure 16 The contribution of gardens takes place through the long-wave emission received by roads and walls (for other calculations refer to [START_REF] Lemonsu | Inclusion of vegetation in the Town Energy Balance model for modeling urban green areas[END_REF]. Figure 17 represents the new modeling approach that leads to a new architecture of the code.

Within the context of Beirut, the consideration of urban vegetation and their respective impact on UHI is necessary because this would potentially be an important mitigation strategy for the city, especially when considering that Beirut is predominantly covered by artificial surfaces as opposed to natural surfaces (see Chapter 5 for land cover land uses in Beirut). The existing urban vegetation of Beirut city and their impact on UHI could also be analyzed and compared to areas without any vegetative surfaces within the context of this research. This new integrated version of TEB_Veg is therefore deemed very useful for the purpose of this research. Building Energy Model.

The energy consumption of heating, ventilation and air-conditioning (HVAC)

systems in buildings has become an important factor in the design and analysis of urban areas [START_REF] Bueno | Development and evaluation of a building energy model integrated in the TEB scheme[END_REF]. As such, a new building energy model (BEM) was recently integrated into the TEB scheme. Given the increased use of air conditioning systems as a consequence of global-scale and urbanscale climate warming, the integration of the BEM scheme into TEB is considered to be very beneficial as it can help determine and identify those urban geometric and radiative characteristics that result in highest energy demands. Thus, BEM-TEB makes it possible to represent the energy effects of buildings and building systems on the urban climate to estimate the building energy consumption at the city scale with a resolution of a neighborhood (~100m). This approach for TEB was based on an improvement of previous models developed to integrate new building energy models in urban canopy models which are essentially able to capture the mean heat transfer processes that occur inside buildings thus calculating building energy demand, HVAC energy consumption and waste heat emissions [START_REF] Kikegawa | Development of a numerical simulation system toward comprehensive assessments of urban warming countermeasures including their impacts upon the urban buildings' energy-demands[END_REF]Salamanca et al., 2010, cited in Bueno et al., 2012). According to [START_REF] Bueno | Development and evaluation of a building energy model integrated in the TEB scheme[END_REF], previous models considered idealized HVAC systems not taking into account passive building systems.

The new BEM-TEB model that has been developed overcomes the limitations of these previous models. As such, BEM uses a heat balance method to calculate indoor thermal conditions and building energy demand and accounts for solar radiation through windows, heat conduction through the building enclosure, internal heat gains, infiltration and ventilation. An energy balance is thus applied to each indoor surface including wall, window, floor, roof and internal mass, accounting for conduction, convection and radiation heat components.

The same geometric principles applied in TEB are also used by BEM and these include firstly a homogenous urban morphology, where the building enclosure is defined by an average-oriented façade and a flat roof; and second a glazing ratio where BEM assumes that all building facades have the same fraction of glazed surface with respect to their total surface.

In addition, buildings in BEM are assumed to be in a single thermal zone where all buildings in a particular urban area have the same indoor air temperature and humidity thus calculating the overall energy consumption of a building or neighborhood as opposed to a building zone. BEM also assumes an internal thermal mass which represents the thermal inertia of the construction materials inside a building such as the separation between building levels. Finally, BEM assumes that the surface of the building in contact with the ground is well-insulated (see Figure 18 which represents the main physical processes included in BEM-TEB).

Within the context of UHI analysis in Beirut therefore, the TEB-BEM is potentially very useful for assessment of the diurnal energy demand of buildings in the city since heat emissions from HVAC systems can indirectly impact the UHI. This option for BEM could also be useful for example for simulation of future scenarios for a specific mitigation strategy, like urban greening, being considered for Beirut city. It is therefore a good indicator of whether the selected mitigation scenario has a cooling effect on the city or not.

Conclusions

TEB has been validated in several measurement campaigns [START_REF] Lemonsu | Simulation of a summer urban breeze over Paris[END_REF][START_REF] Lemonsu | Modeling of the surface energy balance of the core of an old Mediterranean city: Marseille[END_REF][START_REF] Masson | Evaluation of the Town Energy Balance (TEB) scheme with direct measurements from dry districts in two cities[END_REF]

Finite Volume

Model. [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF] developed an atmospheric modeling scheme that moved away from the traditional approach typically adopted in mesoscale models (which consist of modifying the roughness length at the surface and the thermal properties of the ground) since they failed to reproduce the vertical structure of the turbulent momentum fluxes and the urban heat island effects.

According to [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF] these failures are due mainly to the fact that the shadowing and radiation effects of buildings are neglected. Another reason is attributed to the fact that the only sink of momentum is at the ground and is not distributed up to the higher buildings. Martilli accordingly developed a new model that corrected these failures capable of representing the impact of urban buildings on airflow at the mesoscale (see [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF] for a complete description of the model). The model is referred to as the Finite Volume Model (FVM) and represents the city as at least one urban class that is characterized by the following parameters [START_REF] Roulet | Validation and application of an urban turbulence parameterization scheme for mesoscale atmospheric models[END_REF]:

 Shape of the street canyon, expressed in terms of the distance between building rows, and shape of the buildings, expressed in terms of roof width and wall height (see Figure 19)

122 nu Ju=iu
 Building height distribution, expressed in terms of the probability γ of having buildings with a certain height Ɀ and a density Γ of buildings higher than given values of Ɀ (see Figure 19); γ and Γ are linked by the following equation:

Γ( Ɀiu ) = Ʃ γ ( Ɀju)
(Equation 8)

Where nu is the highest level in the urban grid.

 Street orientation (several orientations per class are possible)

 Properties of the materials (thermal diffusivity, heat capacity, albedo, and emissivity for the three urban element types, i.e., street, wall, and roof. The module therefore calculates turbulent fluxes and meteorological scalars for any given street direction while allowing for the specified building height distribution, and then averages over all defined street directions. This urban parameterization scheme is implemented as a sub-grid of the mesoscale grid in the FVM mesoscale model. The horizontal resolution is identical with the resolution of the mesoscale grid, while the vertical resolution must be finer than the mesoscale resolution and is usually selected to 123 be of the order of 2 to 5 meters (the sub-grid extends vertically only up to the highest building). After their calculation in the urban grid, the fluxes and meteorological variables must then be vertically interpolated in the mesoscale grid [START_REF] Roulet | Validation and application of an urban turbulence parameterization scheme for mesoscale atmospheric models[END_REF].

According to the available literature the TEB and FVM appear to be similar in their modeling approach although the TEB model is described as a single layer urban canopy model as opposed to the FVM which is described as a multi-layer urban canopy model. In a paper by [START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF] which compares the various different modeling schemes that have been developed for study of urban energy surface-atmosphere exchange processes, he recommends using single-layer urban canopy models for the surface energy balance (SEB), such as the Town Energy Balance (TEB) scheme of [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF], where there is direct interaction with one atmospheric layer above the uppermost roof layer but recommends using multi-layer models, such as the FVM developed by [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF], for more specific analysis objectives such as the impact and feedback between canyon air and air-condition (see Figure 20). [START_REF] Hidalgo | Advances in urban climate modeling[END_REF] explain the workings of the FVM modeling scheme as the "buildings of different height" approach since all building heights must be identified within a grid cell (see Figure 19).

Therefore, due to the higher complexity involved in the FVM scheme, which requires more detailed urban data values (like for the case of determination of each building height within a grid cell), the TEB scheme is perceived to be the more feasible of the two mesoscale models discussed thus far for the Beirut case especially when considering the limited data available for buildings as well as general associated data on urban form in Beirut (see Chapter 6 of this thesis for more details). (2001) and is in fact an urban canopy model similar to that developed by [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] and is also used for meso-scale studies. In their paper, [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF] introduce this simple single-layer urban canopy model for use in atmospheric models and compare it to two sets of observations concentrating mainly on air temperatures and net longwave radiation in Vancouver, British Colombia. While both [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF] and [START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF] mention the similarities of their two models, the differences are also explicitly defined. [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF]

Summary.

As can be seen from the above literature review on the existing urban surface exchange models therefore, most of these modeling schemes are based in one form or another on the surface energy -atmosphere balance equation, with some variations as to the specific urban parameters that are considered in the models simulations such as anthropogenic heat, street orientations, building heights, wind velocity, and so on. Another main difference lies in their scale of use, where some are used at the building or neighborhood scales while others are used for city scale or even global scale climatic simulations.

Based on this literature review therefore, the most suitable choice for the UHI modeling scheme for Beirut was found to be the TEB model since it is the most adequate model for analyzing UHI in large scale studies. In addition, TEB does not require data for individual buildings which is advantageous within the context of this research since data of this sort is limited in Beirut (see Chapter 6). Table 6 is a summary of the various urban surface exchange modeling schemes described above.

Mitigation Strategies to Combat Urban Heat Island

The available literature on measures and schemes to mitigate or minimize the impacts of UHI is exhaustive as plenty of work and research has been carried out in this regard in densely populated cities worldwide. While this aspect of the literature review does not attempt to cover all the existing literature on this topic, it does provide a classification of these measures into three main categories commonly implemented and practiced and gives examples of successful results and researches conducted based on these respective categories of mitigation measures. These categories include 1) implementation of urban vegetation; 2) implementation of cool surfaces; and 3) implementation of both urban vegetation and cool surfaces. ambient cooling. Shade trees intercept sunlight before it is able to warm a building and urban forests cool the air by evapotranspiration [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF]. Wind speed is also decreased under the tree canopy of shade trees which are also able to shield buildings from cold winter breezes. The energy demand for air-conditioning use is also reduced by urban shade trees, air temperatures are lowered and the overall urban air quality is improved by reducing smog. On the other hand, trees planted along streets and in parks where they do not offer direct shade to air conditioning buildings exert an ambient cooling effect sufficient to have a substantial impact on smog formation [START_REF] Gartland | Heat Islands: Understanding and Mitigating Heat in Urban Areas[END_REF].

Green roofs have also been shown to have significant mitigating effects on urban heat islands. In a study on the effect of rooftop gardens on energy consumption of a building in Singapore, [START_REF] Wong | The effects of rooftop garden on energy consumption of a commercial building in Singapore[END_REF] were able to show the major difference in surface temperatures of surfaces with and without vegetation (Figure 22). This is therefore an important mitigation scenario for the UHI in Beirut. (see also Chapter 2 literature review of this thesis for more details on urban vegetation and their role in cooling surrounding urban environments).Table 7 gives examples of successful implementation of this mitigation measure.

132 Figure 22. Temperatures of surfaces with and without vegetation. Source: Wong, et al., 2003, pp. 358 4.3.2 Implementing cool surfaces. Implementing cool surfaces (including rooftops and pavements); implementation of "cool roofs" or roofing surfaces with high solar reflectivity (like white coated roofs), has resulted in very low differences between the surface and ambient air temperatures, only up to about 10oC. On the other hand, for dark roofs which are highly absorptive and which have low albedo properties, the difference between the surface and ambient air temperatures may be as high as 50oC. At the building scale, a dark roof is heated by the incoming solar radiation which directly raises the summertime cooling demand of the building beneath it. However, cool surfaces are capable of reducing the summertime cooling energy use of the buildings (Akbari, et al., 2001;[START_REF] Akbari | Potentials of urban heat island mitigation. Prepared for: International Conference on Passive and Low Energy Cooling for the Built Environment[END_REF]. Cool pavements also have the advantage of lowering urban heat islands because more of the incoming light is reflected back into space resulting in cooler surfaces and ambient temperatures. In contrast, dark pavements (typically asphalted) increase heating of the city by sunlight because a dark surface absorbs a lot of the incoming solar radiation thus getting warmer. The pavements then heat the ambient air temperature and help create the urban heat island. Figure 23 shows the temperature differences 1.5m above the ground between dark asphalted pavings and cooler granite pavings. This UHI mitigating scenario is therefore considered to be an advantageous one for Beirut (see also Chapter 2 literature review part of this thesis for more details on albedo and solar reflectively of urban materials). Table 7 gives examples of successful implementation of this mitigation measure. 7).

Pavement watering.

Pavement-watering has been studied since the 1990s and is currently considered to be a promising tool for urban heat island reduction and climate change adaptation. Indeed a recent study in the city of Paris showed that application of this specific technique reduced street surface temperatures by several degrees further to analyses carried out using infrared camera measurements which therefore had positive effects on pedestrian comfort [START_REF] Hendel | Improving a pavementwatering method on the basis of pavement surface temperature measurements[END_REF]. In Japan, this method for cooling of urban spaces has been studied since the 1990s and has also shown overall positive effects [START_REF] Kinouchi | Cooling effect of watering on paved road and retention in porous pavement[END_REF]. Having said this it is worth noting that future water resource availability must be considered and accordingly optimized should this strategy be selected as a suitable UHI mitigation measure [START_REF] Hendel | Improving a pavementwatering method on the basis of pavement surface temperature measurements[END_REF]. The cooling effect is attributed to the transpiration process of water which helps to release the trapped heat in asphalted pavements (especially during periods of intense incoming solar radiation) which is the type of material typically used for pavements in Beirut for example. For the case of Beirut, given the widespread awareness for more sustainable use of water resources as a result of the water deficit across the country (MOE/LEDO/ECODIT, 2001; CDR. NPMPLT /DAR-IAURIF, 2004) 17 , this scenario is not suitable for the Beirut context 18 . 4.3.5 Summary. Hence, these aforementioned mitigation strategies not only improve the thermal comfort levels of urban dwellers, but also reduce energy demand levels thus also minimizing air polluting emissions or anthropogenic heat and therefore also indirectly lower impacts on the UHI effect of a city. For the case of Beirut, implementation of these mitigation strategies may have significant impacts in reducing urban canyon temperatures and cooling energy loads of buildings. As such, except for the 17 The average annual volume of water input in Lebanon via rainfall and snowfall amounts to ~9,300Mm 3 and the losses which occur via evapo-transpiration, surface flow in streams, and groundwater (with losses outside the national boundaries into the sea and to neighboring countries, and un-exploitable groundwater and sea-springs) leaves ~ 1,830Mm3 or only 20% of the incoming water volume (CDR. NPMPLT /DAR-IAURIF, 2004) 18 It could be argued that the planting of urban vegetation scenario previously discussed also essentially requires water intake which would therefore not be a sustainable strategy for Beirut. However the existing urban tree types in Beirut (namely ficus nitida and pinus pinea), which would also be proposed in future planting strategies for the city should this be found to be a suitable mitigation scenario for the city (see Chapter 7), do not require high water intakes per day (see Chapter 6 for details on existing vegetation). 135 pavement watering scenario, this research considers the aforementioned mitigation measures in scenarios devised specifically for the purpose of this research to find measures most suitable for alleviation of UHI of Beirut city from an urban planning and design perspective (see Chapter 7 of this thesis).

Table 7 gives examples of case studies worldwide that involve implementation of one or more of the aforementioned UHI mitigation measures and with successful results. -This paper anlayzes the thermal performance of a small green space (0.24 ha) and its influence on the surrounding environment of a densely urbanized area in Lisbon. It was found that the garden was cooler than the surrounding areas, either in the sun or in the shade. These differences were higher in hotter days. Besides the local weather conditions, the low wind speed, the sun exposure and the urban geometry are the potential factors that explain these differences. It was concluded that green spaces in urban areas can therefore create a cooling effect which is more pronounced in cities with UHI and during hot and dry days in cities with a Mediterranean climate. Singapore -This study carried out simulations to determine the effects of rooftop garden on the annual energy consumption and cooling load of a fivestory hypothetical commercial building in Singapore. In these simulations, three different types of roof (exposed roof, typical flat roof, roof with rooftop garden) were simulated and the effects of the rooftop garden with different types of vegetation and the variation in thickness of soil were also considered. The study accordingly showed that the installation of rooftop garden in a five-storey commercial building could result in a saving of 1-15% in the annual consumption and 17-79% in the space cooling load. The optimum type of rooftop garden was found to bte rooftop garden with shrubs (300mm thick soil and shrubs) could achieve a saving of 15% in the annual energy consumption and 79% in the space cooling load. In addition, the optimum type of soil was found to be the rooftop with clay soil (dry). This type of rooftop could achieve a saving of 3% in the annual energy consumption and 64% in the space cooling load.

Athens, Greece

-A modeling study was undertaken to assess the urban heat island effect over Athens, a densely populated city, by trying to analyze the impacts of large-scale increase in the albedo of building rooftops on ambient temperatures. The study showed that adopting large-scale high albedo measures by using building materials with high solar reflectance can significant reduce ambient temperatures. In addition, city-scale application of cool materials will results in a reduction in energy consumption by reducing both direct radiative heating of buildings and ambient temperature and will improve thermal comfort levels in outdoor spaces.

Syneffa, Dandou, Santamouris, and Tombrou, 2008 Not specific to any one city or case study -This paper quantifies the effect of increasing the albedo of urban areas on global warming. Although it focuses on global warming and not specifically the urban heat island, the concept remains valid also for mitigation of urban heating. The paper emphasizes that in many urban areas, pavements and roofs constitute over 60% of urban surfaces. As such, increasing the albedo of urban surfaces (including roofs and pavements) can reduce the summertime urban temperature and improve urban quality. The paper concludes that using cool roofs and cool pavements in urban areas, on an average, can increase the albedo of urban areas by 0.1. -This paper conducts a study for the city of Sacramento and shows that it is possible to raise the overall albedo of urban surfaces, namely roofs, accordingly producing significant energy savings and at the same time increasing comfort within the city. First the study shows that there is indeed potential to increase the overall albedo of roofing within the city by identifying that 20% of the 96 square miles area is dark roofing and 10% is dark pavement. Some programs that would support solar-reflect urban improvement are also identified in this paper such as labeling of paints and roofing materials according to their temperature in full sun; marketing programs and information materials to aid consumers in the selection of solar-reflective materials; low-coast loans for solarreflective surfacing and so on. The paper concludes that the albedo of Sacramento city can be increased by 18% overall. Salt Lake City, Utah -An urban heat island pilot project was conducted for the Salt Lake City of Utah by the Lawrence Berkeley National Laboratory (LBNL) and U.S. Environmental Protection Agency (EPA). Thermal aerial photos were first taken to identify the main "hot spot" areas (or areas which generally correspond with urban developments). Surface cover data also helped scientists to indicate that Salt Lake City's heat island can reach 4 o C at night and about 2 o C during the afternoon. The area extent of Salt Lake City's heat island was also found to be greater in the afternoon compared to earlier in the day. LBNL concluded that Salt Lake City could increase their additional tree cover by approximately 13%. In addition, LBNL found that with 49% of the city's surfaces being impermeable (roofs and pavement), there is a large potential for solar reflectance modification starting with the impermeable surfaces. Similar pilot projects were conducted for the cities of Chicago, Baton Rouge, Houston and Sacramento.

U.S. EPA Urban Heat Island Pilot Project: Profile of Salt Lake City. http://www.epa.gov/

Pavement-watering

Paris, France

-Street temperatures were investigated on Rue du Louvre in Paris, France during the summer of 2013. Watered and control weather stations were erected although only data from the watered site were studied. Surface temperature measurements were made using an infrared thermal camera which was placed on the roof terrace of Rue du Louvre, approximately 20m above street level. The pavement was watered over a total of 10 days during the summer. Pavement watering was found to reduce morning temperatures between 2-4 o C and between 6-13 o C for afternoon surface temperatures. Surface wetting is indeed found to decrease pavement albedo thus lowering reflected shortwave radiation which can otherwise negatively affect pedestrian comfort. However this approach is expected to increase air humidity caused by watering which may negatively affect pedestrian comfort. In all it was found that watering pavements helps reduce formation of UHI in Paris. [START_REF] Hendel | Improving a pavementwatering method on the basis of pavement surface temperature measurements[END_REF] Japan -In this study, the effect of watering on the road and the retention in porous pavement is investigated. Watering on the pavement is considered to produce significant urban cooling. Watering on the surfaces of pavements was conducted using watering pipes buried in the center of roadways. The field observation was accordingly conducted on August 13 from 9AM to 3PM for two sites, one within the area to be watered (site A) and the other about 30m away from this site (site B).

Watering was conducted from 10AM to 2PM. Observations showed that the average temperature measured at Site B was higher than that at Site A during the time of the watering. For the experiment performed to see the effect of water retention in porous pavements it was found that during the period of watering which was supplied to the pavement once a day from 13 until 15 August, the maximum temperature decreased by 14-18 o C. When there was no water supply after 15 August, the surface temperature rose again to around 55 o C due to the reduced suction water in the porous pavement therefore highlighting the significant effect of watering on alleviation of surface porous pavement temperatures.

Kincouchi and Kanda, 1998

Part III of this thesis is comprised of one chapter and gives a detailed description of the case study area including its physical characteristics, climatic conditions, and urban populations. In addition, it gives an historic overview of urbanization and urban planning processes in Beirut, since these processes helped shape the urban morphology of Beirut as we know it today thus giving a clearer understanding of how the city has been planned

and where planners, architects and engineers have channeled their main focus of attention for the development and growth of the city or lack thereof. The land cover and land uses are also outlined here, along with the city's zoning scheme which has been adopted. The relevant legal framework is also discussed as well as the key players in the urban planning sector in Beirut. Finally, the dominating urban surfaces in Beirut and their respective solar properties are determined in this chapter.

The aim of this chapter is to identify the urban parameters of the city, based on the aforementioned assessment of the city's urban characteristics, which contribute to the urban heat island effect thus raising the thermal discomfort levels of urban dwellers and accordingly lowering the overall quality of life. This chapter therefore justifies why there is a need to carry out measurements and modeling of the UHI in Beirut in the view to emphasize the importance of this phenomenon in Beirut and to accordingly propose mitigation strategies from an urban planning perspective.

Chapter 5: Beirut Case Study

Introduction

While the history of urbanization of the city of Beirut shows a marked expansion of the city from the 1800s to present day, there is no evidence showing that the environment, urban climate or the UHI for that matter were ever considered by architects, engineers or even urban planners while European cities like London and Stuttgart for example analyzed the climatic conditions of the study from as far back as 1818 and 1938

respectively in order to better understand the relationship between urban development and climate and to take action accordingly. This disregard for the UHI in Beirut/Lebanon could be attributed to the fact that major advances were made in the study of this phenomenon only recently and more specifically within the last three decades when the first publication of the International Journal of Climatology took place soon after its establishment in 1981 [START_REF] Arnfield | Two decades of urban climate research: A review of turbulence, exchanges of energy and water, and the urban heat island[END_REF]. The civil war could be regarded as another reason for this delay or disregard for such a significant urban climatic phenomenon where other more pressing issues like survival and safety were top on the list of priorities for the citizens of Beirut.

Urbanization, when not planned, controlled or managed in a sustainable manner, can contribute to shaping an urban morphology which can have exacerbating effects on the UHI phenomenon. This in turn can have serious implications on thermal comfort levels and human health leading even to mortality [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF][START_REF] Chagnon | Impacts and responses to the 1995 heat wave: a call to action[END_REF][START_REF] Shahmohamadi | Mitigating the urban island effect: some points with altering existing city planning[END_REF][START_REF] Dhainaut | Unprecedented heatrelated deaths during the 2003 heat wave in Paris: consequences on emergency departments[END_REF][START_REF] Hartz | Climate and heat-related emergencies in Chicago, Illinois (2003-2006)[END_REF][START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF][START_REF] Oliveira | The cooling effect of green spaces as a contribution to the mitigation of urban heat: A case study in Lisbon[END_REF][START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF]Colombert, Diab, Salagnac, and Morand, 2011).

The following sections therefore give an account of the history of urban planning of Beirut, as well as the physical, climatic and urban factors that characterize the city and that accordingly contribute to the exacerbation of the urban heat island phenomenon of Beirut. increased modification of natural surfaces, and more pressure on energy demands, on road infrastructure and accordingly increased anthropogenic heat emissions and so on.

Physical and Climatic

Although this thesis does not investigate the direct impact of urban populations on the UHI, it does carry out analysis indirectly via the effects of the urban form and material compositions of the artificial city as a result of the rising urban populations in Beirut.

Beirut, an artificial city

After having discussed the various underlying physical and climatic factors and demography of Beirut city, this section gives an account of the history of urbanization, urban planning and urban zoning processes that have shaped the urban form of Beirut as it exists today, and the legal and institutional framework of the urban planning sector in

Beirut, which all contribute to the effects of the UHI of this city.

This section also assesses the main land cover and land uses of the city, its urban morphology, the dominating urban surfaces of the city and their respective albedo or solar reflectivity properties. What makes these factors important within the context of the UHI study for the city is first the characterization of the main land uses and therefore the assessment of the extent of artificial versus natural surfaces and second the identification of the material composition of the respective urban surfaces within specific land covers and land uses along with their respective radiative and thermal values. For example, in areas primarily defined as artificial surfaces the majority of these urban surfaces like rooftops and pavements are impermeable with predominantly low solar reflectivity or albedo properties (since these surfaces are primarily asphalted in Beirut) that can significantly aggravate the UHI. In contrast, land uses that are characterized or defined as parks or vegetated surfaces have the reverse effect with important cooling impacts on the UHI as a result of the evapotranspiration processes of trees and plants. Moreover, the urban morphology of a city contributes significantly to exacerbation of the UHI where for example building heights, street width, height/width ratios, street orientations, all factors of urban geometry, contribute to UHI effects as discussed in Chapter 2. This section is therefore divided into the following six parts: 1) an historic account of the urban planning and urbanization events which helped shape the urban morphology of the city of Beirut;

2) zoning extent and specifications of Beirut; 3) the legal and institutional urban planning framework; 4) assessment of land use-land covers characterizing the city of Beirut, 5) the urban morphology of Beirut, and; 5) the albedo or solar reflectivity of the dominating urban surfaces including buildings and roads. The main aim of this chapter is to identify the main urban factors that can potentially have the most significant effects on UHI.

History of Urbanization, Urban Planning and Environmental

Considerations in Beirut. There are numerous important references on the historical evolution of Beirut city with emphasis on the impact of governing mandates and sectarian diversities on the respective urbanization and molding of the morphology of Beirut as well as the more specific details on the urban, suburban, peri-urban and rural areas in and around Beirut [START_REF] Davie | Beyrouth 1825-1975: un siècle et demi d'urbanisme[END_REF]Khalaf & Said, 1998;[START_REF] Rowe | Projecting Beirut: Episodes in the Construction and Reconstruction of a Modern City[END_REF][START_REF] Saliba | Beirut 1920-1940: Domestic architecture between tradition and modernity[END_REF]Yassin, 2012). Within the context of the aim of this research to identify the urban geometric parameters that have the most significant contribution to the effects of UHI, it is important to understand the history of urbanization of the city that has resulted in the development of an urban morphology that characterizes the city as it exists today. One central and recent reference (Yassin, 2012) which aims to illustrate the evolution of Beirut, explains the marked expansion of the city from the 1800s to present day with development that took place in almost all directions (see Figure 29). According to Yassin (2012), within the context of urban planning and development, the city of Beirut passed through five main stages of development as follows: 1) the Ottoman Empire(1840s-1920); 2) the French Mandate ; 3) the Independent Era ; 4) the civil war period , and; 5) the post-war period (1992-present). Table 8 gives a detailed outline of the history of the key urbanization and urban planning practices that took place within these five development stages and identifies whether any respective environmental considerations were given as such, specifically to the urban microclimate.

In summary, based on Table 8 and the available literature on the topic it can be concluded that in fact urban planning took place haphazardly in Beirut with very little consideration being given to the environment or urban microclimate. Urban planning of Beirut was therefore offset by the various different development stages mentioned previously which are linked primarily to the political situation of the country (mandating powers, wars, and so on). For example, in 1948, Lebanon witnessed a large influx of Palestinian refugees into the country as a result of the political instability in their territories which resulted in the establishment of numerous camps across the country including Beirut (see section 1.5.1.1 for more details on these Palestinian camps). In addition, as a result of the widespread unaffordable housing situation, informal settlements also started to materialize but mainly outside of the city's boundaries starting in the 1960s (see section 1.5.1.2 for more details on informal settlements in the city).

Moreover, after the Lebanese civil war period, the private company "Solidere" became highly involved in the reconstruction and reshaping of the city center (see section 1.5.1.3

for more details on Solidere's associated works for the city center). These aforementioned events that include the mandating powers and regional or civil wars, the establishment of Palestinian refugee camps, and the associated important works of Solidere all helped shape the urban form of the city as it exists today.

Therefore these urbanization events that took place are very important when considering the main events which molded the urban form of Beirut city and which resulted in the choice or selection of the dominating urban surface materials of the city that potentially have a significant impact on UHI and which is the main context of this research.

.

Refugee camps.

In Beirut, there exist two Palestinian Refugee Camps known as "Shatila", and "Mar Elias" (see Figures 30 and31). Established in the 1950s as temporary settlements for a large refugee population, these camps eventually turned into permanent elements of the urban context of the city of Beirut and formed a base from which urbanization spread to surrounding areas whenever the possibilities of expansion were available [START_REF] Fawaz | Informal urban development/the Lebanese experience/brief overview[END_REF]. Thus, according to Fawaz, some of these camps have increased their area since they were first established becoming part and parcel of the urbanization of the city and affecting the overall transformation of Beirut. Indeed the housings within these camps do not follow modern standards of building and urban regulations. Table 9 provides brief information on these camps including the year in which they were established and their respective populations (Fawaz and Peillen, 2002;[START_REF] Fawaz | Informal urban development/the Lebanese experience/brief overview[END_REF][START_REF] Martin | From spaces of exception to 'campscapes': Palestinian refugee camps and informal settlements in Beirut[END_REF][START_REF] Martin | From spaces of exception to 'campscapes': Palestinian refugee camps and informal settlements in Beirut[END_REF]. While this thesis does not investigate specifically the extent to which the buildings or structures within these camps impact the UHI, it can potentially be an interesting and important topic to consider for future researches within the context of UHI for Beirut city. Having said this, these camps are integrated within the overall analysis of the UHI for Beirut city.

Solidere.

Another important event worth mentioning here, which is contributing to the shaping of the urban form of Beirut is associated with the developmental and urban planning activities of the private company "Solidere".

Following the civil war period, Solidere became actively involved in master and urban planning projects primarily for the Beirut Central District (BCD) area which covers approximately 1.9 km 2 (Figure 32) of Beirut administrative area. Their activities include the establishment of guidelines and detailed plans defining the rules and regulations of construction and urban development and these also include defining land uses and land covers (http://www.solidere.com/corporate/services/master-urban-planning). Figure 32 represents the Master Plan for BCD where most of these projects have been implemented, such as the marina area currently referred to as "Zaytouna Bay" (no. 9 on the map) and the traditional old souks area known as "Beirut Souks" (no. 5 on the map), with a few others still in progress. Within the context of the UHI, the urban development activities of Solidere may or may not be contributing to the exacerbation of the UHI of the city of Beirut especially as Solidere is involved in land uses and land covers within the 1.9 km 2 of land owned by Solidere. In fact, Solidere undertook a major project which involved the reclamation of vast areas of land in "Biel" which can have significant impacts on the UHI due to obstruction of wind patterns for example as a result of the newly constructed buildings on this reclaimed piece of land (labeled as "Reclaimed Zone" in Figure 32). On the other hand, Solidere is planning public parks and squares within the city (labeled no.

7 in Figure 32) which can have major cooling effects of the urban vegetation on the city's UHI. While this thesis does not aim to specifically investigate the impacts of Solidere's construction and planning works on the UHI effect, it can be considered as an interesting and important topic for future research work for the city of Beirut. While the reclaimed zone is not considered in this thesis due to unattainable data, the rest of Solidere's land is integrated along with the overall UHI analysis of the city.

Beirut's urban zoning.

In the year 2000, decreed master plans covered 1,091 km 2 (10.4%) of Lebanon, while un-decreed master plans covered an additional 614 km 2 (5.8%)these master plans await their corresponding decree. Therefore, until 2004, the total area of Lebanon covered by master plans (approved/decreed and approved/non-decreed) was about 1,705 km 2 . The remaining area (83.8%) is unplanned and only partially surveyed. Therefore this implies that from a land use point of view, the most complex areas (i.e., coastal zone, urban poles and their suburbs), including the Beirut case study area, are already zoned (MOE/UNDP/ECODIT, 2011).

The urban planning and zoning for the city of Beirut was originally developed by Michel Ecochard in 1963 (see Table 8) to which some minor modifications, not pertaining to the zoning specifications per se, were made in the year 2007. This urban plan divides the city into 10 zones (see Figure 33), each with its own specifications for surface area of building plots, lots subdivisions and so on.

Out of the various zoning specifications, the specification of relevance for the purpose of this research is the building height, where higher buildings reduce the sky view factor thus significantly impacting the UHI of a city. For zones I and II, reference is made to Decree 5714 (under Solidere ownership) where the maximum permissible heights for buildings under these zones are listed. For zone 3 a calculation is provided for the building height (H=2.5[R1+L+R2] 20 ), while zones 4, 5, 6 and 7 have no specified building heights in which case reference is made to the Building Code#646 (see subsequent section for more details on Building Code #646) which provides the methodology for calculation of building height, typically around twice the width of the street and pavements on which the building is to be constructed, similar to the calculation 20 In this calculation for building height, "R" refers to the pavement width and "L" refers to the road width provided for zone 3 above. Therefore if the road is 6m wide for example, the building can go up to maximum 12m height.

Zone 8, which falls primarily in Moussaytbeh cadastral area, is divided into 6 additional sub-zones and has the most detailed zoning specifications and the reason for this could potentially be because the most recent urbanization in the history of Beirut took place in this part of the city (see Figure 29) and therefore it was possible to integrate more zoning criteria within these undeveloped areas at the time of Ecochard (see Appendix II for a full list of the zoning specifications for Beirut). Indeed, specifications for building heights are listed for some but not all zones including zone 8, where for example the maximum building height is 17m for subzones 8.A.I and 8.A.I.4 while there are no height specifications for the other 4 subzones.

As for zone 10, which falls under Ras Beirut cadastral area, and which is subdivided into six subzones, only subzones I, II, and IV have specified heights for buildings where in subzone I, maximum permissible floor number is 7 and subzones II and IV have maximum permissible building height of 9m. Finally, for Zone 9, Zone 10.

III and Zone 10.V these are listed as "servitude non-aedificandi totale" which implies that they are non-constructible zones reserved mainly for public utility such as pathways, areas in the sea port or airport, or any right-of-way passage.

In the case of the aforementioned high rises which are fast becoming more prominent features in the skyline of the city, these require special permits from the Council of Minsters (COM) which accordingly issues a decree in order for the developer to proceed with the construction works for buildings who's heights surpass the maximum permissible limit.

168 Within this zoning scheme for Beirut therefore, the main specification of relevance within the context of UHI analysis is the building height because as discussed in the literature review chapter of this thesis, buildings that are relatively high and spaced close to each other can have a more significant impact on trapping incoming solar radiation thus preventing the emitted heat from escaping back into the atmosphere and accordingly aggravating the heat island. Indeed this scenario is considered in the numerical analysis chapter of this thesis (Chapter 7) in order to illustrate the potentially significant effects of these high rises on the UHI of the city in the view to propose sustainable design and planning recommendations accordingly (see Chapter 7). construction otherwise no construction is permissible. Non-construction zones can also be determined.

-Article 9: zones that have not been planned can be placed under study for a period of up to two years further to a decision made by the Ministry of Public Works and Transport, and after consultation with the HCUP and the relevant municipality.

During these two years however no construction is to be permitted. Forested areas are not allowed to be destroyed and the natural landscape of the area should not be changed.

-Article 17: no monetary compensations will be provided for changes to any restrictions on building coefficients, including setbacks, number of floors, building height, and colour, which plays an important role in protecting public health and safety or the natural environment.

-Article 19: relevant authorities may expropriate private land for the benefit of the public good by compensating the respective landowner(s) with a nearby land of equal value.

-Article 20: relevant authorities may carry out re-parceling of previously zoned areas in order to facilitate urban planning.

-Article 23: government or relevant municipality may ask the landowners of residential areas nearby forested areas or natural open spaces to swap their land with another piece of land.

-Article 24: municipalities or union of municipalities can agree with landowners of forest or natural sites to open these areas as public areas or parks and municipalities can accordingly change admission fees for maintenance or upkeep.

As can be seen, the Urban Planning Law #69 of 1983 took important foresight with regards to urban planning measures to help protect the environment although there is still room for improvement within the context of implementation of urban planning practices to minimize impacts on UHI or urban microclimate but these are discussed in more detail in later sections (see Chapter 9).

Building Code #646

Moreover and more recently, another relevant law was issued in the building and construction sector, namely the Construction Law 646 (dated 2004) also known as the Building Code (see Appendix IV for a copy of extracts from the Building Code #646 of Lebanon in Arabic). The first construction laws of Lebanon stem from Beirut during the late 1800s. At the time, the municipality of Beirut developed building regulations that were subsequently adopted by other municipalities in response to the densification of certain areas and neighborhoods. Today, it is the Construction Law #646 that is the centerpiece of all construction activities in Lebanon. This code introduced some important changes to benefit the construction sector while at the same it introduced some requirements for the protection of the environment and landscape. These specific changes that are advantageous for the safeguarding of the environment are listed in Table 10 below (MOE/UNDP/ECODIT, 2011): Changes introduced Environmental implications Increase in the validity period of a construction permit from 4 to 6 years with the possibility of another 2 years extension This article implies that the construction period is extended for a longer period of time so for example in cities this affects neighbors and pedestrians for a longer time via the generation of dust, noise, and prolonged obstruction of sidewalks. As for villages, unfinished buildings can have a negative impact on the landscape. Fortunately, Article 3 of this law issues fines for buildings that are not completed within the permit period of a maximum of 8 years, although this period is still relatively long where associated impacts on the environment including the urban microclimate are prolonged and linger. Every additional underground car park, above and beyond what is prescribed in the construction law, will be exempt from taxes:

This article is an incentive for developers to maximize underground floor space thus having lower impacts on natural lands if available. Unfortunately though, in practice, underground construction is expensive and although impacts on ambient air are minimized, the incentive to increase car ownership for a single family is maximized with associated impacts on UHI via anthropogenic heat emissions (although the latter is not investigated in this research since the focus lies primarily on urban fabric and form and their respective impacts on UHI in the view to find urban planning mitigation solutions) Article 13 of the construction law requires that construction and demolition activities comply with environmental regulations pursuant to Environmental Law 444/2002 (see Appendix V) This article identifies conditions for not granting construction permits such as safety, public health, landscape and architectural components. It also allows for urban planning authorities to require developers to provide additional infrastructure including wastewater treatment plants (WWTPs) and green areas. whereby the latter requirement is an advantage within the context of UHI mitigation Staircases and elevator shafts are excluded from the calculation of building coefficients on the condition that they consume less than 20m 2 floor space In practice, this implies that buildings exceed the legal building coefficient by 20m 2 which reduces water infiltration further. Small parcels are now more attractive to developers. Reduction in water infiltration increases water runoff and may even cause flooding especially during the rainy season. Increasing impermeable surfaces exacerbates the urban heat island Looking at Table 10 therefore it is evident that there are no specific building codes to minimize impacts on the urban microclimate such as the specific requirement for "cool materials" for rooftops and facades of building for example although it does mention implementation of green areas in Article 13 as seen in Table 10 which can potentially have significant alleviating effects on UHI of Beirut if indeed applied. Some other obvious green elements in the current version of this amended construction or Building Code #646 include the requirement to plant trees, to properly ventilate all areas of buildings, and to encourage installation of solar hot water systems for all building owners. Therefore it does consider some green elements although unfortunately, this Building Code in its entirety, and not specifically for the selected articles in Table 10 above, is not regimentally applied by the concerned professionals in the field, including architects and engineers, since it does not allow for flexibility in design and due to a major deficiency in a robust implementation and reporting regime by the relevant authorities. Recommendations and suggestions within the context of UHI mitigation strategies are discussed in later chapters of this thesis (see Chapter 9).

Institutional Framework

Regarding the institutional framework of the urban planning and land management sector in Lebanon, the following key actors are involved, the majority of Table 11 provides a list of these aforementioned stakeholders involved in the urban planning sector in Beirut with a description of their associated responsibilities in this respect. The key purpose of this table is to identify the main role of these various parties and whether their responsibilities include any consideration of the protection of the urban microclimate of Beirut. Therefore as can be seen from Table 11, there are several key stakeholders involved in the urban planning sector in Beirut but unfortunately communication amongst and between these parties is not efficient and actions toward achieving more sustainable urban planning practices are weak. An example of an NGO actively involved in advocating sustainable urban planning measures but not involved as a stakeholder and therefore not listed in Table 11 is the Lebanese Green Building Council (LGBC) 24 .

LGBC provides stewardship towards a sustainable built environment and accordingly promotes, spreads and helps implement high performance construction concepts that are environmentally responsible and healthy and that provide incentives to implement designs that take into consideration the urban microclimate. Indeed most of the incentives towards achieving a more environmentally conscious city are being taken by such NGOs 23 "mokhtar" is a person who is the head of a local government of a town 24 LGBC acts on market, educational and legislative issues to achieve its goals (www.lebanon-gbc.org). It offs a Lebanese certification system for buildings, known as "Arz", that adopts environmental parameters and transforms the way buildings and communities are designed into a prosperous and sustainable environment which do not have as much influencing power as the governmental authorities like the Municipality of Beirut or the Directorate General of Urban Planning. There is therefore much room for improvement in this respect and this is discussed in more detail in later chapters (see Chapter 9). As such, according to this latter classification, Beirut is again described as an "artificial area" (level 1 classification), comprised of both "urban areas" and "activity areas" (level 2 classification). Table 13 gives a clear outline of the various levels of land use land cover categories. Based on these classifications therefore, it is concluded that Beirut is an "artificial area" with a mix of all level 2 classifications that include "urban areas", "activity areas", "non-built-up artificial areas" and "artificial, non-agricultural vegetated areas".

Land cover

Consequently, "urban areas" in Beirut are indeed comprised of both a "continuous urban fabric" and a "discontinuous urban fabric". Within the predominantly continuous urban fabric characterizing the city of Beirut, there is typically a mix of largely dense urban fabrics and dense informal urban fabrics (namely the Palestinian refugee camps).

Within the remaining smaller fraction of areas defined as discontinuous urban fabrics within Beirut, there is typically a mix of medium density urban fabrics, some tourist resorts and a few scattered archeological sites.

As for Level 2 areas identified as "activity areas", the city of Beirut includes all categories listed in Table 13 except for railways, since only remnants of these remain as they have not been operational since around the 1970s. Under level 2 areas identified as "non-built-up artificial areas" there are no mineral extraction sites, or landfill sites, or airport, which lies outside of the administrative boundary of the city of Beirut toward the south. Moreover urban vacant lands are typically asphalted areas which serve primarily as parking lots.

Therefore upon comparing these two sources that classify land uses and land covers in Beirut it is seen that in fact there is not much difference between the two, considering that the more recent one, the NPMPLT, is based on the one prepared prior to that by the MSC-IPP Environment. Having said this, the NPMPLT classifications consist of more broken down and explanatory descriptions of the specific land cover categories.

Reference is thus mainly made to the NPMPLT classifications in this thesis since this is a more recent document and has in fact been endorsed as a decree hence is considered as a more official reference.

Figure 35 presents the main category of land uses within the city of Beirut, according to the NPMPLT classification, which categorizes Beirut primarily as territoire artificializé or artificial/built-up/urban area comprised of a combination of residential, commercial and industrial zones. Some green urban areas are also seen on this map of Beirut where the largest ones exist namely at the AUB institutional campus grounds and the pine trees public garden known as Horsch Beirut. These urban parks/gardens cover approximately 2% and 1.75% of the entire Beirut administrative area respectively. There are however no water bodies (artificial or otherwise) within the city of Beirut. There is only one seasonal river which runs just outside the eastern boundary of Beirut administrative area (see Figure 35) but this remains mostly dry during the summer season Therefore, the majority of the land cover land use in Beirut is artificial (>90%) (buildings and roads) with a small percentage of the remaining land being covered by urban vegetation.. corridors, and open spaces, and green spaces, all play a combined role in shaping the urban morphology or urban form of a city. As mentioned, the history of urbanization of Beirut and the various associated 'development stages' played a key role in shaping the urban form of the city as we know it today. While a detailed account of these urbanization stages has already been given, this section is dedicated to the key urban morphological characteristics that formed as a result of these development stages. These characteristics are deemed important for the purpose of this research as they can contribute significantly to the UHI effect of the city as mentioned in the literature review chapter of this thesis and can accordingly affect the results of the simulations.

For the case of Beirut, the urban morphology was molded and shaped by the two main governing and ruling authorities at the time namely, the Ottomans (1840s -1920), who left their mark on the city's architecture and design, but only a couple of these structures are left standing today like the Grand Serail situated in the downtown Beirut area, and the French who also played a role to this effect as reflected in the buildings architectures and the city's planning attempts by Ecochard and the Danger Brothers. The Independent Era , especially under the presidency of Fouad Chehab (1958Chehab ( -1964)), also witnessed major transformations of the urban morphology of the city with significant improvements in infrastructure combined with major development and construction projects. However, during this period, the Arab-Israeli war resulted in the influx of many Palestinians into the country and the consequent establishment of refugee camps which had a significant impact on the urban morphology of the city (see previous section 1.5.1). The civil war period (1970s-1991) on the other hand was a destructive period and resulted in massive internal displacements of hundreds of thousands of inhabitants who fled their original rural areas of residence and settled in informal squatted settlements which expanded and grew in an unorganized and sporadic manner, taking up land surfaces and producing small low-quality housings in the outskirts of large cities such as Beirut and Tripoli. Beirut received the largest share as the main urban center of the country, with fleeing residents settling down mainly in the outskirts of Beirut in the 'misery belts' of Beirut suburbs. At around this time, the Council for Development and Reconstruction (CDR) was established, in order to better control and govern the various urban developments and planning that the city was in such dire need of. This period also witnessed the ratification of Urban Planning Law 69 which was issued further to modification of the previous Urban Planning Law of July 24 1962 (see Appendix III for a full copy of Urban Planning Law 69/1983 in Arabic).

Finally, the post-civil war period (1991 to present) witnessed gradual changes in the urban morphology due to increasing population densities of the city, with about 21,000 inhabitants / km 2 (Population and Development Strategies Programme Lebanon, 2014; MOE/LEDO/ECODIT, 2001) ). These changes involved mainly improvements in road transportation networks as well as development projects that include typically tearing down and replacement with newer and taller buildings. Throughout its history of urbanization, the environment has not been considered in the planning of the city, although in the summer of 2012, the Ministry of Environment's (MOE) environmental impact assessment (EIA) and strategic environmental assessment (SEA) decrees were finally ratified, which oblige consideration of environmental as well as climatic effects of new proposed development projects as well as policies (see Table 8 for history of urbanization and environmental considerations in urban planning in Beirut).

A closer look at the urban morphology of the city shows that upon taking a grid cell of 200x200m size in Mazraa area for example (see Figure 36 where the grid cell is represented in red), which is situated toward the south of the city in what is identified primarily as Zone 4, the urban fabric is defined by a large mass of closely spaced buildings of heights up to 12m or less (or 4storeys) and primary and secondary roads with widths ranging between 8-10m, and with very little urban vegetation (represented in green). Upon looking closely at this image, it seen that there are three buildings with redtiled rooftops, which are typically lower in height reaching up to a maximum of 5-6m (or 2 storeys) but as clearly seen these are not the dominating building types in this area of Mazraa or even in the entire Beirut city area. There is also a significant surface area of open spaces, characterized mainly by paved parking lots hence this area is characterized as a dense urban fabric. According to the urban plan of the city there are no specifications for maximum building height in this specific zone of Beirut in which case reference is typically made to the Building Code #646 of Lebanon. Upon looking at a cell size of similar size in Ras Beirut on the other hand, situated along the coastline and primarily in Zone 10, the urban fabric is found to be less dense than the inner and eastern areas of the city, with a lower density of buildings but these are again closely spaced just as in the Mazraa area, although roads or highways are more clearly defined here and again urban vegetation is sparse (Figure 37). This area could therefore be described as having a medium density urban fabric. Furthermore, Ras Beirut is characterized by average buildings heights that are almost twice that in Mazraa, reaching up to and over 20m in most cases. The maximum allowable height for buildings in this zone is in fact limited to 7 storeys which is equivalent to approximately 20m height. Beirut is therefore typically characterized by a combination of dense to medium urban fabrics and dense informal urban fabrics (such as the "Shatila" and "Mar Elias" Palestinian refugee camps). Green urban areas are scarce and scattered throughout the city and the transport networks are widely distributed throughout the city making up for a large fraction of the city's urban surface. Therefore the predominantly dense urban fabric of Beirut city which is comprised primarily of artificial surfaces and with varying street orientations, building heights as well as height to width ratios, can all play a significant role in exacerbating the UHI of the city. Some of these latter urban geometric characteristics are indeed investigated in this research as discussed in later chapters (see Chapter 7). However, the intensity of the UHI impact can also be highly impacted by the solar reflectivity or albedo of the material compositions of this dense urban fabric which is discussed in the subsequent section.

Albedo values of dominating artificial urban surfaces in Beirut.

As mentioned previously, the dominating artificial urban surfaces in Beirut (as opposed to natural surfaces) which can potentially have a significant impact on the UHI or urban microclimate are comprised of buildings, which include facades and rooftops, and roads.

Depending on the albedo property of these surface urban materials, the impact on UHI can be significant whereby the lower the albedo the higher impact and vice versa. This section focuses primarily on the main material composition and accordingly albedos of the dominating artificial surfaces in Beirut. As such, regarding the typical wall materials in Beirut, as illustrated in Figures 39 and40, the majority of new as well as old buildings in the Beirut area have light coloured walls composed primarily of beige/white paint or plaster. According to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] 26 , these materials have a high albedo (α) typically as high as 0.7. Thus walls are not expected to have significant impacts on UHI in Beirut. fact, most developers opted for concrete covered rooftops during the construction boom in Beirut which took place mainly during the Independent Era between 1940s and 1970s, concrete covered rooftops in contact with the ambient air can significantly raise the internal building temperatures and additionally affect the UHI of the city. Having said this, it is not uncommon to find that recently some owners of old building in Beirut are replacing their rooftops with lighter coloured coatings, typically white in colour such as limestone or white paint, which generally have higher albedos; the main purpose of this is because owners are suffering from the internal heating effects of the low solar reflectivity of these concrete covered rooftops and have found that this approach can lower the heat stress significantly. Having said this, the majority of the buildings still appear to have concrete covered rooftops. According to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] the albedo (α) for concrete is 0.225 which is quite low therefore rooftops in Beirut are considered to have significant impacts on UHI. Finally, the third dominating urban surfaces in Beirut, roads, are comprised mainly of asphalted surface layers which have an albedo (α) of 0.2 [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. In fact, in Beirut there are three classifications of roads including primary, secondary and tertiary and the main material composition of all three of these road classifications is asphalt.

Therefore since asphalt has a very low albedo value of 0.2, it is expected that the impact on UHI of Beirut is significant.

Hence rooftops and roads, the dominating urban surfaces in Beirut and with highest exposure to incoming solar radiation, have very low albedo (α), as compared to the facades of buildings in Beirut, and accordingly play a major role in exacerbating the UHI. The extent to which these urban surfaces impact the UHI is one of the chief objectives of this research with the aim to find mitigating solutions for the urban planning of the city as such. Scenarios are accordingly devised and analyzed and these are discussed in detail in Chapter 8 of this thesis. Table 14 is a summary list of the albedo (α)

of the material composition of the outer layer of the dominating urban surfaces in contact with the ambient air in Beirut city as adapted by [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF].

Importance of Investigating Urban Heat Island in Beirut

Based on the above detailed account of the predominantly artificial land cover of Beirut, the small percentage coverage of urban vegetated surfaces, the dense urban fabric and haphazard urban morphology of the city, and the low albedo values of the dominating urban surfaces in Beirut, it is evident that these all contribute to the urban heat island of the city and the respective deterioration of a good quality of life of urban dwellers. This section aims to show that while sustainable urban planning practices are being implemented in many densely populated cities worldwide and with successful results, very few efforts have been made for Beirut. The need to investigate and find solutions for UHI in Beirut is discussed in this section, which is divided into the following sub-sections: 1) sustainable urban planning practices worldwide; 2) haphazard urban planning practices in Beirut; 3) previous climatic and UHI studies in Beirut, and; 4) conclusions and justification for UHI analysis in Beirut.

Sustainable urban planning practices in developing countries

worldwide. While it is clear that urbanization and industrialization activities improve our material lives and daily comfort they also induce many problems to the surrounding environment, and consequently human health. Consideration of the environmental discipline in urban planning is fast becoming the norm around the world especially with the ever increasing demands and pressure from a legal perspective (EIAs, SEAs and the like). Architects, planners, and environmental experts are joining forces to implement sustainable practices and measures for the future growth and development of cities.

Voluntary programs like green building programs are also becoming increasingly popular with rewarding results. As such, cities in developed as well as developing countries worldwide are making major efforts in their quest toward reducing air pollution levels, implementing green areas, gardens and parks, improving public transportation systems, implementing green buildings, and organizing campaigns for raising overall environmental awareness. Examples of such cities include Thailand, Bogota, Curitiba, Denmark, London, Vancouver, Sydney, Barcelona and many more (UNEP [United Nations Environmental Program], 2010). Such sustainable steps are necessary especially when considering the significant rise in population growth, depletion in natural resources, the resulting impacts on the urban microclimate and the consequent effects on the health and comfort of urban citizens.

Haphazard urban planning practices in Beirut.

For the case of Lebanon, a small country situated along the Mediterranean Sea, increasing urbanization trends and expansion of its major metropolitan cities of Beirut and Tripoli are being witnessed.

Unfortunately, an overview of the history of urban planning practices in Beirut clearly

shows that the existing urban morphology of this city has been molded primarily as a result of the wars and governing mandates that lasted for relatively short periods hence interrupting and disturbing certain urban planning trends initially being practiced and or implemented. For example, regional strife in the 1940s resulted in the influx of Palestinians who accordingly resided in informal refugee camps in the city and across the country thus affecting the existing urban morphology of the city. In such instances, very little consideration was given to the protection of the environment or sustainable planning due mainly to the urgency of the situation to accommodate and house the refugees. These haphazard planning events are the cause of a fast decline in the surrounding environmental quality, including air quality, and urban microclimate (SOER, MOE/UNDP/ECODIT, 2011). Table 8 which provides an overview of the history of urban planning in Lebanon has clearly shown that the environmental context only recently started to be considered in relevant laws and regulations while implementation of protection measures is just barely taking place.

As such, when considering these haphazard trends of urban planning practices in Lebanon, the increasing urban populations (Yassin, 2012), the dominating artificial land cover land uses, and the dense urban fabric and complicated urban morphology, it is evident that impacts on the urban microclimate are significant what with the increasing warming trends 27 , and the resulting increases in heat-related deaths [START_REF] El-Zein | A time-series analysis of mortality and air temperature in Greater Beirut[END_REF].

Vulnerability to the impacts of urban microclimatic changes in Beirut is therefore high. Upon considering the importance being given to climatic adaptation measures in similar dense cities worldwide, like Athens, the Abu Dhabi, Paris, London, and so on, it 27 As previously mentioned within the context of the CIRCE studies conducted for Beirut showed an increase in the number of hot days especially during this past decade in Beirut 199 is concluded that it is important to quantify the UHI in Beirut to identify areas of greatest impacts and to determine the urban parameters that play the most significant role in this regard. The objective is to provide recommendations for mitigation of the UHI from an urban planning perspective in order to improve the overall quality of life and to prevent heat-related deaths (see Figure 42). However, some investigations on climate change and to a certain extent on UHI in Beirut have been conducted as discussed in the subsequent sections. ), the sensitivity of human settlements and infrastructure (including wastewater, solid waste, and transport) to climate change is also assessed. As such, although not emphasized per se, the issue of the urban heat island effect is briefly mentioned where the study explains that the increase in hot summer hot days due to climate change will result in intensification of the urban heat island phenomenon (Chapter 9,.

Previous climatic and UHI studies in

The major urban agglomerations coupled with the drastic land use changes are listed as being the major reasons giving rise to the UHI. Although it has been recommended to carry out dynamical downscaling experiments to provide more accurate data input for sector impact studies in future works, it has not been mentioned that it would be helpful to actually include urban heat island investigation as part of this downscaling exercise.

Another study worth mentioning within the context of the urban heat island and urban design disciplines in Lebanon includes two UNDP reports on "Climatic Zoning for Buildings in Lebanon" and the "Thermal Standard for Buildings in Lebanon (UNDP/GEF and MPWT/DGU 2005) 28 . In the first study, Lebanon is divided into four climatic zones (Coastal, Western Mid-Mountain, Inland Plateau and High Mountain) where Beirut falls under the Coastal zone area. These climatic zones were established based upon the review and assessment of four main climatic parameters including temperature, humidity, solar radiation and wind, which all play a major role in impacting the heating and cooling energy requirements in buildings. The second study establishes the thermal standards for buildings in Lebanon based upon their respective climatic zones although one drawback of this study is that it is applicable only to new residential buildings and complexes and does not offer solutions to improve the building envelope of existing residential buildings. Having said this, considering that there are significant numbers of "old" buildings that are being demolished and replaced by new buildings (~0.6%), like in Ashrafiyeh, Moussaytbeh, Minet El Hosn, and Ras Beirut areas amongst others, these energy-efficient building standards are important and can prove to be very effective29 . It is worth noting that these studies indeed mentioned that the reason for the hot microclimate of Beirut is the UHI phenomenon without elaborating any further as this was not the aim of these studies. Two other related studies include the Energy Efficiency Building Code Study and Energy Efficiency Building Road Map (MED-ENEC/EU, 2012) which emphasize the importance of making energy efficiency a fundamental part of the building design and construction process and which accordingly provide the roadmap for successful implementation for Beirut case. Unfortunately these thermal standard codes for buildings and the road map have not yet been approved by the relevant authorities and have therefore not yet been properly adapted. Implementation of these energy efficient thermal building codes would be a major milestone for a sustainable and green development of buildings in Beirut.

A study on the health impacts of urban warming was also carried out focusing on heat-related mortality for the city of Beirut [START_REF] El-Zein | A time-series analysis of mortality and air temperature in Greater Beirut[END_REF].

This study concluded that there exists a very strong positive correlation between heat related mortality at moderately high temperatures in Beirut and is therefore a serious public health risk in this city which is experiencing increasing hot summer days.

Finally, an important study worth mentioning involved climatic model simulations to investigate the extent of the urban heat island of the Mediterranean cities of Athens, Alexandria, and Beirut (McCarthy, 2009). In this study, the Met Office Hadley Regional Climate Model (RCM) was used to downscale climate change projections from the Hadley Center Global Climate Model. The RCM typically runs at 25km for a limited area and provides high resolution climate projections. However, even at 25km, variations in land surface types are poorly resolved. To resolve this problem for weather forecasts and climate change studies, the Met Office developed "tiled" surface scheme (similar to TEB) to conduct simulations of the urban heat island in the aforementioned Mediterranean cities. This tiled scheme allows for sub-grid scale variations at the model surface. Each model grid box is composed of a varying mix of five vegetation types (broadleaf tree, needle leaf tree, grass and shrub), and four non-vegetation surfaces (bare soil, inland water, ice, and urban). The transport of heat and water (and consequently near-surface temperature, and humidity) between the atmosphere and surface is then calculated explicitly for each surface type within the grid cell as shown in the schematic in Figure 43. The urban tile within the MOSES2 is utilized to provide representation of cities at sub-grid resolution. In this study therefore, the urban tile is modeled in a simple way by introducing a canopy that has the thermal properties of urban elements. This canopy is radiatively coupled to the underlying soil scheme. Figure 44 is a schematic representation of the surface energy balance of the urban canopy model [START_REF] Best | Evaluation of the urban tile in MOSES using surface energy balance observations[END_REF]. Best, et al. 2006, pp. 506 In this scheme therefore, the surface energy balance for urban and other tiles is as follows:

Q*=K*+ε s L↓-ε s σT s 4 (Equation 9)

Where: Q* is the net all-wave Radiation, K* the net shortwave radiation, L↓ the downward long-wave radiation, ε is the emissivity and σ the Stefan Boltzmann 30 constant. 30 The Stefan Boltzmann law describes the power radiated from a black body in terms of its temperatures. The Stefan Boltzmann constant is the constant of proportionality in the Stefan-Boltzmann law.

resulting in low heat capacity of soil and vegetation surfaces which in turn yield a large diurnal temperature range in the region. The urban tile therefore reduces the night cooling rate resulting in a larger night time urban island for the Mediterranean in the summer as seen for the case of Beirut for example where a large summer diurnal temperature range for non-urban areas around Beirut resulted in a large UHI in excess of 7 o C during the summer season (July and August), while in Athens and Alexandria, the simulated average night time UHI was found to be much less, at an order of 2 o C to 3 o C, bearing in mind that the model was aiming to also replicate the results of previous studies. Figure 45 shows the UHI magnitude of minimum temperatures of these three modeled cities and illustrates the large UHI magnitude found for Beirut in comparison to the cities of Alexandria and Athens for the aforementioned reasons, namely the low soil moisture characteristics assumed for the Mediterranean region. dense Mediterranean city but mainly because of the nature of the data input into the tiled scheme not to mention that approach that was used to replicate data from previous studies. Nevertheless, this was the first study that was conducted for the UHI in the Mediterranean region including Beirut where the simulations provided a preliminary indication for the growing significance of this phenomenon over Beirut (and Alexandria and Athens) and its associated implications on the environment although it applied a rather broad and simplified scheme for its simulations.

Conclusions and justification for UHI analysis in Beirut.

Based on the above overview of the haphazard urbanization trends in Beirut, the rising urban populations due to rural exodus, the low albedo of the dominating urban materials, the rising number of hot summer days especially over this past decade, and the associated human health impacts and heat-related mortality, it is imperative that more detailed studies are carried out to investigate the urban parameters of the existing urban form of the city which have the most significant effect on UHI. Although a preliminary analysis of UHI in Beirut was previously conducted [START_REF] Mark | CIRCE Climate Change and Impact Research: The Mediterranean Environment[END_REF], this study adapted a very simple scheme for conducting the analysis, based on a regional climatic model, which did not take into consideration the main urban parameters that can exacerbate the UHI effect as such and which can accordingly be corrected if the proper urban planning measures are implemented. In addition this analysis did not consider different scenarios which could potentially be implemented to identify the best mitigation solutions and actions from an urban planning perspective for the city of Beirut. This is in fact the context of this thesis therefore which first assesses and identifies the urban characteristics of greatest significance on the UHI of Beirut and which accordingly proposes mitigation measures within the context of the sustainable urban planning of the city.

Part IV of this thesis on the UHI in Beirut is comprised of the following two main chapters: 1) the research methodology adopted for this research including the rationale for the selections made with regards to measurement type and modeling scheme for the Beirut case, and 2) the numerical analysis which includes the simulation results of the UHI in Beirut based on the collected data which are run on TEB and the specific scenarios devised for the purpose of this research and the results.

Chapter 6: Research Methodology

This chapter describes the specific methodology adopted by this research to conduct an analysis of the urban parameters that play the most significant role in exacerbating the UHI in Beirut to consequently recommend feasible mitigating solutions from an urban planning perspective. The chapter is accordingly divided into four main sections: the first and second sections explain the rationale made for the selection of the most suitable measurement type and modeling schemes for UHI analysis in Beirut respectively; the third section identifies the nature of data required to carry out the simulations on TEB in Beirut, and; the fourth and final section of this chapter describes the data collection process, the gap between the required data and the availability of data and respective measures taken to overcome this gap giving an account of some associated challenges during this process.

Selection of Measurement Type for Beirut Case

The literature review part of this thesis gave an outline of the various type methodologies typically employed for UHI measurement and these included fixed and/or mobile traverses, high resolution aerial orthophotos and thermal remote sensing techniques. In this chapter, several criteria are selected and used upon which the decision for most feasible type-methodology for temperature measurements for the Beirut case was based. These criteria include namely: 1) associated costs; 2) coordination with relevant authorities; 3) permitting processes; 4) equipment availability; 5) training requirements; 6) timeline; 7) traffic congestion; and 7) allocation of suitable equipment set-up locations as necessary (see Table 15). This section is therefore divided into two parts: the first describes the elimination process and the second describes the collection of data from existing weather stations which are selected for the purpose of this research. First, the choice of using fixed or mobile traverses to measure the urban diurnal temperature patterns over a set period of time be it winter or summer season, or both, was not found to be feasible. This was due to the high associated costs required to purchase the necessary measuring instruments; although specific quotations were not obtained for these instruments, some inquiries showed that this would indeed prove to be the case. Another constraint involved the potential difficulty in finding suitable locations to set up the instruments since this would require coordination and official no-objection certificates or permits from the relevant authorities, involved property owners and concerned municipalities. The application of this type-methodology would have been time-consuming and the results may in all probability not have been very reliable especially given the uncertain political situation in the country as well as in the region, and where sectarian strife may have potentially prevented or interrupted continuous and proper measurements. Similar obstacles were associated with mobile traverses where such equipment that can typically be installed on bicycles or cars for example would have been difficult to obtain due to the associated costs, unavailability, and potentially long shipment times if purchased. Traffic congestion would have been another one of the main problems encountered if measurements were to be conducted by application of this methodology at a specified time of day or night taking into consideration the significant traffic congestions in and around Beirut whether during or off-peak hours.

Second, the choice of using high resolution aerial orthophotos also proved to be challenging, the reasons being partly due to even higher estimated costs associated with either the purchase of the high resolution photos themselves, which are not available for sequential years, and which would have been necessary to carry out an in-depth study of the UHI. If the choice of renting aircraft were to be considered, this would have proved to be even more difficult as aircraft in Hence, it was found that the most feasible measurement approach in this regard was to collect pre-existing historical as well as recent present climatic records from the relevant authorities, institutions and concerned parties in order to analyze their relevance for the UHI case of Beirut. As such, climatic records were gathered from two pre-existing weather stations for the purpose of this research including:

1) The old observatory at the AUB located at sea-level on the campus of the university at Latitude 33°54'2.09"N and Longitude 35°28'48.34"E (see Figure 47). This station, surrounded by a dense urban fabric, but which is in fact located in a low-density urban fabric with numerous green spaces, began its operation in 1875 up until 1975, which marked the start of the civil war in Lebanon. Since then, two additional weathering stations have been installed at the AUB campus however it was not possible to attain any records from these university weather stations during the time of this research study even though several unsuccessful attempts were made. Such records are typically provided to AUB students or to authorities that officially request the data but are associated with fees. Having said this, the records obtained from the old observatory, which is readily available in all relevant authorities, was sufficient for investigation of historical or climatic maximum and minimum temperature trends in the Beirut area.

2) The Fanar station, located at approximately 3.5 km to the east of Beirut River at It should be noted that there are indeed three other weather stations situated within or outside Beirut city which were considered (see Figure 47) but which were not found to be suitable for the purpose of this research as explained in Table 16. As a concluding remark therefore, it is worth noting that the weather records from the old observatory at AUB and the Fanar weather station were obtained without any difficulty which made it possible to accelerate the data collection process for at least this part of the research. The records were found to be fully comprehensive without any missing records or information. There was however a difference in the parameters provided whereby for example the records for Fanar were more comprehensive consisting of relative humidity, solar radiation, wind speed, and many other parameters deemed useful for the purpose of this research, while for AUB the records were comprised mainly of minimum and maximum temperature records but dated back from over a century ago which allowed for assessment of historical weather patterns.

1931-Present

Records were not accessible for collection or purchase => not selected

Selection of Modeling Scheme for Beirut Case

Modeling was deemed necessary for the purpose of this research to identify areas of significant UHI intensity in Beirut and to accordingly recommend mitigation measures to reduce the UHI impacts as such. The simulation results help to determine urban geometric parameters that play a key role in exacerbation of the UHI. Thereby, any deficiencies existing in the urban planning, environmental, engineering and architectural sectors would be identified thus giving credibility to future recommendations that would essentially be made for these sectors for alleviation and control of UHI. The concept of UHI modeling and simulations is in itself a novelty for Beirut city.

As such, regarding the choice of the most suitable model to carry out the necessary simulations for the UHI of Beirut, as a start, a rigorous review of the available literature on the topic showed that there are numerous numerical as well as empirical models that have been developed worldwide for the purpose of analyzing UHI (see Chapter 4). Several important comparative studies have also been previously conducted in this regard including the works of [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF], [START_REF] Colombert | Contribution à l'analyse de la prise en compte du climat urbain dans les différents moyens d'intervention sur la ville[END_REF], [START_REF] Grimmond | Initial results from Phase 2 of the international urban energy balance model comparison[END_REF][START_REF] Hidalgo | Advances in urban climate modeling[END_REF][START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF], as well as many others. In this research, an assessment of nine urban surface modeling schemes was carried out whereby the various advantages and disadvantages of these models was assessed and/or highlighted and it was found that in a preliminary step, the Town Energy Balance (TEB) was the most suitable of these models.

In this chapter, the choice for the most suitable modeling scheme for the Beirut context was carried out by a process of elimination. As a start, based on the scale of simulations criterion, three out of the nine modeling schemes that are applied typically for small scale or microscale simulations were eliminated from the list including SM2-U, ENVI-met, and NARPS-LUMPS since the aim of this research is to conduct simulations for the whole city of Beirut and therefore at the mesoscale or the urban planning/town scale. The SVTS model applied for global scale simulations was also eliminated for the same purpose. Then, SOLENE, developed by CERMA laboratory, was also eliminated since it is applied typically for small scale analysis and also due to its weaknesses in assessment of energy consumption of buildings [START_REF] Bozonnet | Modeling methods to assess urban fluxes and heat island mitigation measures from street to city scale[END_REF], a very important factor when considering analysis of UHI intensity in dense urban areas. For the remaining four mesoscale urban modeling schemes, including the two single layer urban canopy models developed by [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF], and [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF], and the two multi-layer urban canopy models developed by [START_REF] Ca | Development of a numerical model for the evaluation of the urban thermal environment[END_REF][START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF], the selection was made by assessing the nature of data as well as the availability of the data required to run the simulations. This was deemed to be an important criterion for the selection process since as previously mentioned there is limited data in the Beirut study area. As such, regarding the single-layer canopy models, it was found that the urban canopy model developed by [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF] requires reproduction of an urban surface consisting of several canyons with different orientations, and therefore more specific data, whereas the Town Energy Balance (TEB) model, developed by [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] considers only one canopy layer characterized by a simple urban fabric, and therefore less data input. As for the multi-layer urban canopy models, it was found that the model developed by [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF] is typically applied for specific analysis objectives such as the impact and feedback between canyon air and air conditioning while the model developed by [START_REF] Ca | Development of a numerical model for the evaluation of the urban thermal environment[END_REF] needs very accurate and detailed data on the volume that is occupied by each building in the canyons for example. Thus, based on this approach and considering the limited data availability for Beirut, the TEB model was selected, which is not attached to the details between existing buildings but rather to the overall characteristics of the urban fabric, and is therefore the most suitable urban surface exchange modeling scheme for the Beirut case. Having said this, this architectural simplification of TEB can in itself be seen as a limitation.

In a similar study comparing six modeling schemes for the city of Paris, including ENVI-met, SOLENE, NARP-LUMPS, SM2-U, TEB and FVM, the application of five select criteria focusing on the nature of data entry and outputs of the model again showed that TEB was the most feasible modeling scheme for analysis of UHI in the city for similar reasons as those discussed above [START_REF] Colombert | Contribution à l'analyse de la prise en compte du climat urbain dans les différents moyens d'intervention sur la ville[END_REF]. These criteria primarily included: fine representation of the built environment; representation of the whole city; consideration of vegetation; heat flux of anthropogenic origin; and, consideration of thermal and radiative characteristics of urban materials. The TEB modeling scheme was found to be sufficient as an indicator for main urban parameters of concern to be considered for the urban planning of Paris just as it was found to be suitable in this research for the case of Beirut. Therefore TEB, which considers mainly building, road, and vegetation fractions, was selected for the purpose of this research. 1. Validity: the use of this model has been validated in several important studies [START_REF] Lemonsu | Simulation of a summer urban breeze over Paris[END_REF][START_REF] Lemonsu | Modeling of the surface energy balance of the core of an old Mediterranean city: Marseille[END_REF][START_REF] Masson | Evaluation of the Town Energy Balance (TEB) scheme with direct measurements from dry districts in two cities[END_REF];

2. Availability: the model can be made available from Metéo France further to obtaining recommendations and filling out all necessary paperwork;

3. Associated costs: the offline version of TEB/SURFEX can be downloaded for free further to receiving the special code and login or alternatively it can be obtained without any associated fees directly from Météo France with recommendation from affiliated academic institutions.

Training requirements: an intensive three-day training course at CNRM at Météo

France in Toulouse, France.

Data Collection and Compilation for Beirut

After having selected the TEB model to conduct the UHI simulations for the city of Beirut, the next step required the actual collection of the data based on the identification of the exact nature of data required to run the simulations on TEB. This section of the research therefore provides details on: 1) determination of the nature of the data required for the assessment and analysis of the UHI in Beirut using the TEB model;

2) the data collection process for the Beirut case; 3) the data which are required but which are not available, and 4) respective measures taken to compile, manage and finalize the required data for analysis of UHI in Beirut using TEB. The flow chart in Figure 49 below illustrates these various steps taken in the data collection process:

6.3.1 Nature of data required to run simulations on TEB. This section therefore describes the nature of data required to run the simulation on TEB. To recap, the SURFEX model is comprised of four main cover fractions (Equation 10) where the TOWN or TEB cover fraction is the tile of relevance for the purpose of this research for Beirut. The TEB tile is comprised of three types of cover fractions representing urban towns including buildings, roads, and, gardens (Equation 11). In TEB, the relevant data associated with these covers can be entered within cells or grid sizes that range from 200 x 200m up to 1000 x 1000m. For the Beirut case the smallest cell size was selected in order to more accurately simulate the required data.

As for the garden part, this includes three types of vegetation covers including high vegetation (HVEG) such as trees for example, low vegetation (LVEG) such as grass, and no vegetation (NVEG) represented by bare soils (Equation 12). Table 17 is a compilation of the nature of data required to run the simulations for analysis of UHI using the TEB/SURFEX model. 10) BLD + ROAD + GARDEN = 1 (Equation 11) HVEG + LVEG + NVEG = 1 (Equation 12)

Climatic records are also required to run or "force" the simulations on TEB. In Beirut city, the weather is fairly moderate during the winter season although records show a warming trend for the summer season over the past decade. Humidity levels are relatively high especially during the summer period considering that Beirut is a coastal city and wind speeds are quite low in general during both winter and summer seasons.

Table 18 is a list of the climatic parameters that are required to force the simulations on TEB for the case of Beirut and generally include wind speed, air temperatures, direct short-wave radiation, and long-wave radiation amongst others. Of course it is worth noting that snow and is not applicable for Beirut as explained in Table 18 below. found that in general there is no single authority in Beirut administrative area that has complete compilation of data as they pertain to buildings, roads or vegetation for example. In addition, obtaining the relevant data was a challenging task because generally the concerned parties were either hesitant to part with the data unless a considerable payment was made or because the data was not considered to be open for public or personal use. A collaborative approach may have been more successful in this regard. Having said this, some authorities were willing to provide the requested data and were helpful. Table 19 is a compilation of the data collected from various governmental authorities and academic institutions in Lebanon. available the data that was collected and compiled was based on extrapolations rather than precise values. In fact, data extrapolation was facilitated by using ArcGIS software 31 . The processes for data preparation of the required urban parameters for analysis on TEB, missing or otherwise, are described in more detail in the sections below.

Buildings.

Due to limited data on existing buildings in Beirut in general, it was found that the most suitable way to gather relevant data was to first determine the age of buildings. As such, all other associated data, including façade and roof materials, and internal floorings, would be able to be determined since respective contractors used typical materials for construction purposes at specific time periods during the history of urbanization of Beirut. For example, during the 1970s, contractors used mainly concrete masonry units for the facades of buildings and painted over them with a thin layer of either white or beige coloured layers of coatings. As for the roofs, no insulation or waterproofing was used at this time, as these were introduced later in the mid to late 1980s. As such, the roofs were either painted with a very thick coating over a relatively thick concrete roof slab (20-30cm) or were just left as is.

Hence, based on historical urban development of Beirut dating from the early 20 th century, the age of buildings in Beirut administrative area was categorized into the following age groups: i) <1948; ii) 1948-1970; iii) 1970-1992; and iv) >1992.

Accordingly, aerial images of Beirut were obtained from the military department "Direction des Affairs Geographiques" for the years 1971, 1998 and 2008 (1:20,000 scale and digital for 2008). These years were deemed sufficient for this step of the analysis although earlier images were available for the 1956 and 1962 but at much smaller scales 31 ArcGIS software which was used throughout this research facilitated the data collection and compilation processes. All data entry and associated calculations for urban cover fractions were carried out on ArcGIS

(1:3750 and 1:5000 respectively). The images were therefore overlaid in the ArcGIS software program and by extrapolation it was possible to match the available digitized version of the existing buildings to one of the aforementioned age groups (see Figure 50).

Those built prior to the year 1948 are few in number, are sparsely scattered, and are generally easily identifiable hence did not require application of this type-methodology.

Instead, site visits were conducted for validation purposes. Since buildings belonging to this age group are few in number, impacts on thermal levels are not considered to be significant. All data that was collected pertaining to buildings was confirmed with the concerned experts and professionals in the field. Table 20 is a list of all data compiled relevant to building facades in Beirut based on their respective age group.

Internal floors.

Data on internal flooring was also required to run the simulations on TEB-BEM. While flooring materials have no direct contact with outside ambient air temperatures and accordingly UHI, their thermal properties, namely thermal conductivity (k) and heat capacity (C), can have indirect effects on UHI since for example the warmer the effects of the respective flooring materials on indoor air temperatures the more significant the demand on energy use via operation of air conditioners, resulting in higher releases of air polluting emissions into the atmosphere thus exacerbating the warming effects of the UHI especially during the summer season.

On the other hand, the cooler the effects of the flooring materials the higher the energy consumption demands during the winter season for domestic heating purposes. The activation of the internal flooring thermal data in TEB falls under the BEM (building energy model) application of SURFEX.

Therefore, once the age of the buildings was verified, it was then possible to determine the internal flooring materials, their respective number of layers, thicknesses and thermal properties which were adapted from Oke (1987) (see Table 22). As before, contractors used typical flooring materials at specific time periods, but not much change was found in this regard from the late 1940s to present day. In fact, contractors typically used and continue to use 5 layers of floorings comprised primarily of the lowermost layer of concrete slab, followed by soft gravel, plaster, terrazzo (from the 1940s to 1970s), replaced more commonly by ceramic, marble or natural stone from the 1970s to present day, followed by the uppermost layer of plaster coating. As reference was being made to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] for the respective thermal values of the flooring materials in question, there was no listing found for 'terrazo' and 'soft gravel'. Approximate values were therefore applied based on other similar materials types. The lower the thermal conductivity (k) of the flooring material, the better the product is at unblocking unwanted heat gain whereas the opposite applies to materials with higher k values. In addition, the higher the heat capacity (C) of a specific material the greater the ability of that material to trap and retain the heat making it more suitable for construction purposes in cold climates. Table 22 is a list of the internal flooring materials typically applied for buildings in Beirut. As can be seen these are generally similar in all age-groups and have generally low to moderate heat capacities and thermal conductivities thus their heat retaining properties are moderate. because glass has a relatively low heat capacity (1.66Jm -3 K-1 x 10 6 ) and can therefore raise temperatures and trap heat inside buildings thus raising internal building temperatures. This in turn sets off the use of air-conditioning systems which impacts the UHI via anthropogenic heat emissions. In TEB-BEM, the parameter of relevance in this regard is the glazing thermal transmittance (KmW -2 ) of glass windows, also typically referred to as the U-value, which is the overall heat transfer coefficient that describes how well a building element conducts heat. Typically, the higher the U value the worse the thermal performance of the building material while a low U value usually indicates high levels of insulation and therefore lower heat emissions and accordingly lower impacts on the UHI.

In Beirut, approximately 90% of the existing building stock was constructed between the 1940s -1970s (see Table 21) but it was not until after the 1970s when double-paned windows started to become more widely used by developers and contractors. Typically however, although the precise statistics is not available, houseowners in Beirut are opting for double-paned windows due to its higher insulation properties and therefore higher energy savings, in which case the single paned windows are being replaced by the double-paned windows. For the purpose of this thesis, it was considered that the majority of the buildings belonging to the 1940-1970 age-group are comprised of double-insulated windows in which case the value 3 KmW -2 is applied in TEB-BEM as opposed to 6 KmW -2 which is the typical U value for single-paned windows.

Another important variable for windows is the fraction of glass in relation to the total area of walls of a building. In TEB-BEM, typically the fraction 15% is applied for buildings described as residential housings while the 40% fraction is applied for multifamily buildings. Since most of the buildings in Beirut are described as multi-storey family / residential buildings, the 40% value is applied. However, it is worth noting that areas of Beirut dominated primarily by hangars (as in the port area and industrial areas) have a lower glass ratio than residential buildings whereby the 15% value would apply.

However, since such areas makes up only approximately 5-7 % of the entire Beirut administrative surface area, they are not expected to have significant impacts on the simulation results hence the 40% value is applied for the control simulation runs.

Roofs.

Regarding roofs of buildings, three main types of roofs are identified in Beirut including: 1) white roofs; 2) grey roofs; and 3) red-tiled roofs.

ArcGIS software program was used to identify these three classifications of roofs by extrapolation on ArcGIS (see Figure 51). These data were validated through site visits as well as meetings with roof contractors, engineers and architects. Table 23 lists based on the number of existing lanes again by extrapolations of aerial images on ArcGIS as follows: 1) primary; 2) secondary; and 3) tertiary roads by extrapolations using the aerial image and discussions with relevant experts. Primary roads are comprised of three lanes, secondary roads of two lanes, and tertiary or local roads primarily of one lane. All road categories are typically asphalted in Beirut area except for the port area (covering a surface area of approximately 1.2 km 2 out of a total of 21.47 km 2 ) which is covered in basalt. Asphalt has a low albedo (α) value of 0.2 while its emissivity (ε) value is high at 0.97 [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. Basalt on the other hand has a much lower α at 0.11 and ε of 0.72.

Primary roads are comprised of one layer of asphalt with 7cm thickness, secondary roads of two layers of asphalt with 5cm and 7cm thicknesses respectively, and tertiary roads of three layers of asphalt with 5cm, 7 cm and 8cm thicknesses respectively. This information was again confirmed with the relevant experts and professionals in the field.

For the purpose of this research, the thermal properties of asphalt were considered in the simulation runs since this is the dominating road surface material used typically for Beirut road surfaces. Open spaces in Beirut area were also identified consisting mainly of parking spaces or other vacant lands with no vegetation or paving. All asphalted open spaces were merged with road cover fraction while those with bare soils were listed under the no-vegetation category with gardens as described in the subsequent section (see Figure 52). These again were validated by conducting random site visits along the streets of Beirut.

In general, trees or high vegetation are mainly comprised of Ficus nitida trees, with heights reaching up to 8m, and Pinus pinea trees, with heights of up to 10m (see Figures 53 and54), while lower vegetation types are mainly comprised of grass found typically in educational institutions and the limited number of public parks in the city. Having said this, it is important to note that there were numerous other vegetation types, including palm trees, olive trees, jacarandas and so on 32 , that were identified across Beirut and which were included in the simulations (see also Appendix VII for a full database on the various tree types identified and included in the simulations in Beirut). The Leaf Area Index (LAI) of these identified vegetation types was then determined. LAI, which is defined as the ratio of total upper leaf surface of vegetation divided by the surface area of land on which the vegetation grows (leaf area / ground surface), determines the interaction between the vegetation surface and the atmosphere. It is considered to play a significant role in UHI, whereby, the larger the LAI of an urban tree for example the larger the shading and cooling provided in an urban canyon thus having greater impact in alleviating the effects of UHI. Generally, the LAI can range considerably from 2 to 5.

The LAI of the identified dominating urban trees in Beirut have values ranging typically between values of 2 and 3 which are considered to be relatively low. It is also worth noting that these urban trees typical in the landscaping of Beirut do not require high quantities of water intake (typically between 1-2mm of rainfall per day).

32 High vegetation types identified across Beirut included: Jacaranda mimosfolia (deciduous), Pinus pinea (coniferous), Ficus nitida, Altea altissimma (deciduous), Phoenix dactylifera (perennial), Brachychiton populneus (deciduous), Albizia julibrissen (deciduous), Olea oleacera (perennial), Cupressus sempervirens (coniferous), Eucalyptus globulus (perennial), among others; low vegetation types identified in Beirut included: Ricinus communis, Nerium oleander among others

Forcing data.

Finally, the climatic records were prepared to act as atmospheric forcing data based upon which the simulations would be run on TEB. As previously mentioned "forcing" describes the prominent climatic conditions in the city that are used to define the boundary conditions for the simulations. Climatic records from the Fanar weather station were extrapolated and computed with the assistance of Météo France experts. These forcing atmospheric data at any given day or time of year were uniform across the entire Beirut administrative area. For the purpose of this research therefore, the months of February and July were selected to represent the results of the simulations during the winter and summer seasons respectively since temperature records show that January and February are typically the coldest months in Beirut while July and August are the hottest months in Beirut (refer to Appendix V for a list of the forcing atmospheric data used for TEB simulations for the months of February and July).

Finalization of data compilation.

Once all the relevant data were compiled they were implemented into the TEB modeling scheme to run the simulations based on existing conditions and on various devised scenarios. Table 24 is an example of six sample cells within the Beirut administrative area showing their respective cover fractions calculated during the data collection process on ArcGIS. As can be seen, each cell is characterized by a distinct urban coverage where each has its specific impact on the UHI of Beirut. Therefore, the data related to the respective urban surfaces, including thermal and radiative characteristics, material thicknesses, vegetation types and LAI values, were identified for each cell within the Beirut administrative area. These were then forced with atmospheric forcing data previously discussed giving simulations for specified output parameters for each cell across Beirut (see Chapter 7).

Challenges during the data collection process

It is worth noting that some difficulties were encountered during the data collection process mainly because of the limited data availability in Beirut. While TEB does not require precise accuracy for data related to individual urban surfaces as compared to the other modeling schemes, the data was still challenging to collect and compile. The reason for this is attributed to the fact there is no documentation or digital information regarding the required data for urban surfaces in Beirut. In addition, not all parties are willing to part with the data they may have since this is usually reserved for collaborative-type works. Accordingly, the data collection and preparation phase was considerably time-consuming. A full list of the compiled data which were prepped for analysis for TEB can be found in Appendix VII of this thesis in a digital CD copy.

Chapter 7: Numerical Analysis

This chapter provides a detailed account of the results of the numerical modeling and analysis of the UHI phenomenon carried out for Beirut city using the TEB urban surface exchange modeling scheme. The collected and compiled data characterizing the existing urban context of Beirut are initially used to run the simulations, in what is henceforth referred to as the 'control run', to observe temperature patterns in different parts of Beirut during both winter and summer seasons. Simulation runs are also conducted for scenarios devised specifically for the purpose of this research. The respective outputs from the 'control run' are then compared against the simulated outputs for the formulated scenarios to assess their significance for the Beirut context. Since the majority of the data was extrapolated, the focus of this numerical analysis is to assess the pattern of the simulated results, as opposed to the real values, to give recommendations for the urban planning and urban development of the city of Beirut with focus primarily on urban geometric characteristics and urban design of the city (see Chapter 8 Discussion).

Control Run

The 'control run' refers to the simulation runs that were carried out using the existing data characterizing the present urban context of Beirut. These include the current dominating urban surface materials and their respective radiative and thermal properties (see Chapter 6). The data were accordingly run on TEB for one entire year using the 2009 forcing data of Fanar weather station with one hour time steps for all grid cells 33 across Beirut city (or that fall within the administrative boundary of Beirut) meaning that outputs were simulated for every hour of every day starting from 0000UTC (equivalent to 3:00AM local standard time) for one entire year. For the purpose of presentation in this chapter all output result for the months of February and July are selected. The choice for February was to allow enough time for TEB to balance out its simulations seeing as these are initiated from the month of January and in addition these months are considered to represent relatively extreme weather conditions for Beirut city although August tends to be the hottest month in Beirut and the coldest months are usually recorded between the months of January and February. Furthermore, it is important to investigate the difference in temperature output simulation results in winter and summer seasons.

Selected cells for simulation runs.

Simulations were carried out across the entire Beirut administrative area (covering 21.47 km 2 ), but for the purpose of this research and for distinct comparisons, several grid cells were also selected for assessments and analyses between areas of contrasting cover fractions. Figure 55 presents the location of these selected cells and Table 25 distinguishes the town cover fractions within each of these cells including the buildings, roads and gardens fractions (which add up to 1.0), all of which are entered into TEB to run the simulations. Results are presented either in the form of graphs for the selected cells or for the entire city of Beirut. urban fabrics thus reflecting the more significant cooling effect of vegetation on canyon temperatures during the summer season. These simulations showing significant temperature during winter and summer seasons also reflect the main characteristics of the UHI which typically decreases with increasing wind speed and cloud cover during the winter (where average maximum wind speed of 10-12 m/s have been recorded in Beirut)

and which is best developed in the summer or warm half of the year (where lower wind speeds of 0.4m/s have been recorded in Beirut). However, it is to be noted that the summer simulation results are generally higher than the average maximum temperature records during this time of the year (at about 35 o C) and these results could be attributed to the sensitivity of the TEB modeling scheme to the very low albedo properties of the roofs and roads in Beirut (see Chapter 7). Having said this it is important to emphasize that this research study does not focus on the exact values of the simulations per se but rather on the pattern of the results obtained.

Comparison between five of the selected cells are also presented in the graphs below (Figures 58 and59). These show clearer distinctions in simulations for areas with differing town cover fractions where higher canyon temperatures are found in the dense urban fabric areas as opposed to the lower density urban fabrics and garden areas. The night-time UHI is also evident in these figures during both winter and summer seasons with higher night-time canyon temperatures in the higher density urban fabrics. This is indeed one of the main characteristics of the UHI intensity which is typically greatest at night.

Therefore, for the control run, the results of the simulations for the canyon temperatures are indicative for the purpose of this research. In general, however, it is expected that the areas of higher elevation in Ashrafiyeh and Moussaytbeh (at >90 m above sea-level) would have cooler temperatures than similar dense urban fabric areas at lower elevations, but indeed not much difference is observed in the simulations for canyon temperatures during both winter and summer. This could be attributed to the similar urban geometries of urban morphologies at both elevations that do not maximize the effects of local climatic conditions. It is also expected that buildings in the dense urban fabric areas would cause a greater shadow effect especially during the winter season due to the lower path of the sun in the sky and the lower intensity of the sun in winter with cooler results than lower density urban fabrics but the shadowing effect of buildings during the winter season is not so significant and occurs only for short periods during the early morning and late afternoon hours and certainly not at peak hours., and in addition the evaporative and cooling effect of urban vegetation on canyon temperatures appears to be far more significant. slabs which have a very low solar reflectivity (α=0.225) and a high thermal capacity (C=2.11) accordingly raising their surface temperatures significantly more than areas with higher urban vegetation [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. Hence, upon comparison of the simulations between these two aforementioned areas a significant ΔT of approximately 20 o C is found (see Figures 60 and61). In this output therefore, TEB results indicate that areas with higher building fractions have the highest rooftop surface temperatures while areas with higher vegetation fractions and lower building fractions, have lower rooftop surface temperatures across Beirut (see Figures 62 and63). Considering that TEB requires input for each building, road and vegetation cover fractions (where the total of these fractions must add up to 1.0 within each grid cell), these results are expected.

Surface roof temperatures are found to go up to 70 o C in areas of dense urban fabric during the summer season (see Figure 61) reflecting the significantly high thermal capacities and low albedo of the concrete roof slab material (C=2.11), which consequently have high impacts on the UHI effect. Again as before, this research focuses on the pattern of the simulation results and not on the exact temperatures per se.

Validations were not carried out to measure the real temperature values of the surface roof materials in this research however this can be recommended in future works when using TEB to compare the results. Results across Beirut therefore show that during the winter day, surface road temperatures are highest in areas with higher road fractions like in Bachoura, Mazaraa and Ashrafiyeh but the ΔT across Beirut is found to be small at this time (at about 1 o C), ranging from about 16 o C, like the seaside, AUB, and Horsch Beirut areas, to 17 o C in the higher road fraction areas (see Figure 64). During the summer day, again simulations for surface road temperatures are highest in areas wherever main or primary road fractions are highest but the ΔT is found to much larger across Beirut at this time (at about 30 o C), ranging from about 43.5 to 73.5 C (see Figure 65). These results are expected due to the higher intensity of the incoming short-wave radiation especially during the summer season and the higher angle of the sun over the horizon thus having a greater effect on areas with higher road fractions and lower vegetation fractions. Indeed such areas have more exposure to the incoming high intensity solar radiations because of the lower shading and cooling effect provided by trees. The latter is represented by the LAI values input parameter in TEB. These results also reflect the important shading effect of trees on surface road temperatures especially during the summer season.

Figures 66 and 67 represent the differences in surface road temperature evolutions between selected cells characterized by high road fractions, like the Port and Bachoura areas, and low road fractions, like the Gardens/Horsch Beirut area, during winter and summer days. Indeed the daily temperature evolutions show that during the winter month of February, there is a ΔT of approximately 2 o C between the Bachoura and garden areas throughout the day, except at midday when there is almost no difference. In July, there is not much difference in ΔT between the port and gardens areas throughout the day except at around midday and during the late afternoon and night-time hours with a ΔT of around 2 o C. These results are attributed to the important shading and evaporative effects of trees during periods of the day when intensity of incoming short-wave radiation is high and during the late afternoon and night-times when air temperatures drop but this impact is not so significant at midday during the winter season and this is because of the lower intensity (and thus lower temperatures) of the incoming short-wave radiation at this time of the year. In addition, the temperature evolution of surface road temperatures is much lower during the winter (rising from about 4 to 18 o C) as compared to the summer (rising from approximately 18 to 70 o C) and once more this can be attributed to the lower intensity of the incoming solar radiation during the winter season thus not having significant effects on raising the surface temperature of roads. Again, this research focuses on the pattern of the simulation results as opposed to real road surface temperatures. Validations could however be considered in future works associated with TEB with real-time measurements.

Therefore, simulation results across Beirut indicate that areas with lower road fractions and higher vegetation covers have lower road surface temperatures reflecting the more significant shading effect of trees in these areas. In addition, according to the daily temperature evolutions during winter and summer, there is not much difference in the simulations between these areas during the winter at around midday while the difference is more significant at this time during the summer. This is expected due to the lower intensity of incoming short-wave solar radiation at winter, while during the summer intensity of incoming solar radiation is higher and the evaporative effect of trees is consequently also higher at midday resulting in the more significant cooling effect of trees at this time of day. At night time when temperatures drop due to the lower intensity of incoming solar radiation trees also further provide shading thus further lowering road surface temperatures.

Wall Temperatures.

The dominating façade material of buildings in Beirut is beige/white paint and plaster (see Chapter 6) and as per [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF], this latter material has a high albedo value (α=0.7) and is therefore considered to be a cool material in contrast to the road surface materials (comprised primarily of asphalt with α=0.2) and rooftops (mainly grey concrete slab with α=0.225). With such a high albedo, it is expected that walls would have the lowest impact on the UHI of Beirut. However, since the mechanism by which TEB functions is based upon the principle of the energy balance equation, and the specific town cover fractions (for buildings, road and vegetation), the combined effect of the radiative properties of the artificial surfaces and the low vegetation covers in some of the street canyons of Beirut city defined as such, results in greater exposure of the walls/facades to the incoming short-wave solar radiation, especially at peak hours, thus increasing wall temperatures comparatively more than areas with higher vegetation fractions (like at AUB campus grounds or the Horsch Beirut park). This pattern is apparent across Beirut during both the winter and summer seasons although during the winter season the temperature differential at midday is small, between about 16 to 19 o C, while during the summer season it is much larger ranging between around 40 and 55 o C as illustrated in Figures 68 and69. temperatures, especially between 11:00 and 14:00 hours during both winter and summer seasons. Figure 72 and Figure 73 show the temporal evolution of the internal building temperatures for five selected cells across Beirut during one winter and one summer day respectively. During the winter it is seen that the HVAC_HT energy system is initiated earliest in areas with highest garden fractions like the AUB campus or Gardens/Horsch

Beirut areas because of the respective cooler internal building temperatures in these areas. During the summer season however, the evolution of diurnal internal building temperature simulations shows that the HVAC_CL is initiated first in areas with higher density urban fabrics like in Bachoura, seaside, port and industrial areas because of the higher internal buildings temperatures in these areas characterized by higher artificial surface coverage. It is expected that internal flooring materials also impact the internal building temperatures. The majority of the building stock across Beirut typically have similar flooring materials (see Table 22) with low to moderate heat retaining properties and are therefore expected to have a comparatively higher impact on energy savings in the winter in areas of dense urban fabrics as opposed to more vegetated areas with lower building fractions (see Figure 72). During the summer again the heat retaining properties of the internal flooring materials across Beirut are expected to have higher impacts on energy demands as seen in the simulation results below (see Figure 73).

Cooling Energy Demand.

In Beirut, annual cooling energy demands take place typically between the months of May to October. After this period, energy demands switch from cooling to heating. Thus, upon simulation of the heating-ventilating airconditioning system (HVAC) or the cooling energy demands (HVAC_CL) across Beirut during summer in July, it is found that as expected, cooling demands are highest in areas defined by a dense urban fabric, such as Bachoura that is defined by a 32% building cover fraction, a low garden fraction of 12% and a high road fraction at 56%, as opposed to the AUB institutional area for example, that is defined by a 28% building fraction, a road fraction of 11% and a significantly high garden fraction of 61% (see Figure 74 and lower density urban fabric along the seaside (12%) and the AUB campus (28%). In Bachoura, results show heating energy demands that go up to 160W/m 2 , at the seaside up to 150W/m 2 , and at AUB up to only 30W/m 2 . These differences can be attributed to the higher building fraction in the Bachoura neighborhood and therefore a greater residential population requiring energy for domestic heating purposes especially during the cold early morning hours of the day. At the seaside however, although the building fraction is significantly lower than at Bachoura, heating energy levels are still closely correlated to the latter area and this could be attributed to the cooler conditions resulting from the relatively larger fraction of the vegetation surfaces (43%), In AUB however, which has the highest garden fraction of the three cells (61%) and much lower resident populations, although an almost similar building fraction to Bachoura at 28%, heating energy demands are found to be the lowest of the three selected cells due to lower living residents (see Figure 76 for comparison of cooling energy demand between the three aforementioned cells and Figure 77 for simulation results across the entire city of Beirut).

In addition, upon assessing the diurnal patterns and trends for heating energy demands, highest levels of energy consumption are found to take place especially during the late night hours when home owners return to their residences after work, the early morning hours before setting off to work, and the early afternoon hours starting from around 15:00, after the incoming solar radiation is no longer at its highest peak. During the summer season, starting from around the month of May to October / November, there is no demand for heating energy as confirmed by the simulation results for HVAC_HT.

264 and heating energy demands were as expected for areas with differing town cover fractions in Beirut. In general, it was seen that TEB is particularly sensitive to roof temperatures and also to cooling and heating energy demands. This is further clarified in the subsequent section on developing scenarios.

Developing Scenarios

Six scenarios were devised to better understand the contribution of each of the previously tested outputs to the overall effect on UHI in Beirut and to make recommendations accordingly for the urban planning of the city. It is worth noting that these devised scenarios to reduce the impacts of UHI of Beirut are realistic considerations for mitigation actions that can indeed be deliberated for a more sustainable approach to the urban planning of the city, particularly where it concerns modifications to the existing urban geometry of the city which is the context of this research. Out of the five previously selected cells therefore and for the purpose of presentation, one cell is selected from the scenarios results and compared against the control run results for the same selected cell with the objective to carry out distinct comparisons and numerical analysis although it is important to note that simulations were carried out for all 446 cells developed across the Beirut administrative boundary. These cells in the following sections were selected randomly to simply illustrate the significance in the extremes in the output results. Table 26 provides a description of these devised scenarios for this thesis. It is worth noting that these devised scenarios are simply modifications or exaggerations of the existing conditions so for example in the case of Scenario 4 (Table 26), the glass ratio is increased from 40% (which is the value applied to the existing glass ratio of existing buildings in Beirut and to run the simulations on TEBsee section 6.3.3.3) to 80% to determine the effect of increasing the glass fraction of buildings in Beirut and their respective impact on UHI of the city. similar approach is applied to the remaining scenarios. Glass ratio increased from 40% to 80% Scenario 4

Building height was increased from 15m to 35m and the roughness length was accordingly modified from 1.5 to 3.5m Scenario 5

Increase in vegetation height from 10m to 25m height Scenario 6

Increase in garden fraction by same amount by which road fraction was decreased (50%) 7.2.1 Scenario 1: Modification of Roof Albedo. For Scenario 1, the roof albedo is increased from 0.2 to 0.7 to assess the impacts of 'cool' materials or high reflecting roof surface materials on the UHI in Beirut since this is a commonly practiced mitigation measure in other similar dense cities [START_REF] Akbari | Rapid development of global heat island mitigation studies and countermeasures: a 30 year success story[END_REF]. The outputs for these simulations included canyon temperatures, roof temperatures, road temperatures, wall temperatures, internal building temperatures, and cooling and energy demands (see Figures 78 to 89).

Simulation results showed that modification of the roof albedo lowered the canyon temperatures by 0.28% during the winter day in February however, during the summer day in July, a much more significant temperature differential of 1.7% or 0.7 o C was found at around 10:00AM when the incoming short-wave solar radiation is at its peak. In the case of surface roof temperatures, simulations during the winter showed temperatures that were lower by 38% (or 15 o C) when results were compared against the control run, while during the summer, simulations showed temperatures that were lower by about 30% or a ΔT of 20 o C. For surface road temperatures, again temperatures were lowered by about 0.17% during midday hours of the winter day, while this decrease was much more significant during the summer day lowering temperatures by approximately 7.5%, especially during the early morning and late afternoon hours. For wall temperatures, these were again lowered by about 0.3% during the winter day at midday, but during the summer day, the impact was found to be more significant where temperatures decreased by about 1% at around 10:00AM. The internal building simulations were lowered by about 1.26% during the winter day and by negligible amounts during the summer day.

However, regarding the heating energy demands during the winter day, these were found to be slightly higher when compared against the control run due to the more significant cooling effect of the roofing materials with their higher albedo properties under this scenario where heating energy demands were raised by about 11.5W/m 2 . Regarding the cooling energy demands during the summer day, these were found to be lower by around 50W/m 2 when compared against the control run, again due to the more significant cooling effect of the higher albedo roofing material under this scenario. Therefore, simulation results under this scenario were as expected.

The results of these scenarios versus the control run are presented in Figures 78 to 89 below. It is to be noted that some of these differences will not appear so significant in the form of graphical presentations but in all cases there is a positive difference, albeit not always substantial, as previously discussed.

Therefore based on these results it is concluded that this scenario is a desirable and feasible mitigation strategy for the Beirut context with generally positive effects on alleviation of the UHI of the city and accordingly the quality of life of urban dwellers. simulations showed higher temperatures which were raised by about 0.75% during the winter and about 1% during the summer. The simulations for the internal building temperatures were also raised but by negligible amounts. As for heating energy demands, these were lowered by a maximum of 5W/m 2 (or 55%) upon comparison with the control run and this could be potentially attributed to the higher wall and roof and internal building temperatures as a result of the higher reflecting properties of the road surfaces affecting the internal building temperatures in the street canyons under this scenario while the cooling energy demands during the summer day were raised by about 90W/m 2 (or 28%) for similar reasons. Again, results under this scenario for increased road albedos were as expected.

Figures 90 to 101 present the comparison of the simulations between the control run and scenario 2. Although some of these presented graphs do not show a significant comparative difference, in all case there is a difference, as previously discussed.

Therefore, based on these results it is concluded that this scenario is not a feasible mitigation strategy for alleviation of the UHI in Beirut due to its associated undesirable effects which occur such as increasing internal building temperatures because of the higher solar reflectivity of the road surfaces and the respective rises in the cooling energy demands of buildings during the summer. BACHOURA-CR BACHOURA-SC2 For Scenario 3, the glass ratio of buildings was increased from 40% (0.4) to 80% (0.8) to assess the effects of buildings with higher glass ratios on the UHI impact in Beirut as new architectural designs in Beirut tend to favor this option. Considering the relatively low solar reflectivity of glass (according to [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF], it is expected that increasing glass ratio of future building designs can have detrimental impacts on the UHI in Beirut.

Therefore, as before the outputs selected for these simulations included canyon temperatures, roof temperatures, road temperatures, wall temperatures, internal building temperatures, and cooling and energy demands. [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]. Regarding road temperatures, simulations showed a small decrease of 0.1 o C (or 1%) when compared against the control run during the winter day but there was increase in road temperatures during the summer day by about 0.5 o C (or 2.5%) especially during the early morning late afternoon hours.

For roof temperatures, simulations were higher than the control run by 0.7 o C (or 5%)

during the winter day and by 0.9 o C (or 3.45%) during the summer day both at around 16:00 hrs. Regarding wall temperatures, a higher temperature differential of 0.4 o C (or 4.75%) was observed throughout the whole day during the winter, and during the summer day the simulations were higher by about 0.2 o C (or 0.95%) when compared against the control run especially in the early morning hours. As for the internal building temperatures, during the winter day the simulations showed warmer results than the control run data by about 0.15 o C (or 0.75%) but during the early morning hours of the winter day (between 04:00 and 08:00) the simulations were found to be lower than the control run by about 0.01%. During the summer day the internal building temperatures were only slightly warmer than the control run by about 0.01 o C (or 0.04%). As such, the heating energy system (which is preset in BEM to initiate when internal temperatures are below 19 o C) is activated just before the control run between the hours of 08:00 and 14:00 during the winter day while the cooling energy system (which is preset to initiate when internal temperatures are above 24 o C) begins again just before the control run between the hours of 12:00 and 18:00hrs. Regarding the cooling energy demands, these were found to be higher than the control run by up to 180W/m 2 especially when the incoming short-wave solar radiation is at its peak and this is attributed to the good insulating property of glass and the relatively low heat capacity of the increased glass ratio of the buildings (1.66 Jm -3 K -1 x 10 6 ) [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] thus raising quickly the temperatures inside the buildings and consequently keeping the temperatures inside the buildings fairly constant. As for the heating energy demands, these are again found to be higher than the control run by about 25W/m 2 especially during the early morning hours of the day and late evenings and this can be attributed to the combined effect of the lower intensity of the incoming solar radiation at these times and the fairly low conductivity of clear glass (k=0.74 Wm -1 K -1 ) [START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF].

Therefore the simulations for the outputs under this scenario with increased percentage of building glass ratio were as expected. Since some of these differences in results are not so significant, they will not be clearly visible if presented in the form of graphs, therefore for presentation purposes only the simulations results for heating and cooling energy demands are presented here (see Figures 102 and103).

Based on these results therefore, it is concluded that increasing the glass ratio of buildings is not a suitable design measure for buildings in Beirut since it exacerbates the overall UHI of the city and accordingly lowers the quality of life and thermal comfort level of urban dwellers. As for the heating and cooling energy systems, the raised canyon temperatures resulted in higher cooling energy demands when compared against the control run by approximately 40W/m 2 (or 12%) especially at midday when the intensity of the incoming short-wave radiation is at its peak. During the winter day however, due to the raised canyon temperatures, heating energy demands were approximately 10W/m 2 (or 10%) less than the control run. The simulations for the heating and cooling energy demands were as expected and it appears that activation of the BEM option in TEB has the highest impact on the heating and cooling energy demand simulations under all 4 scenarios thus far.

Therefore under this Scenario 4, considering that TEB is a single layer canopy model where there is direct interaction between one atmospheric layer above the uppermost roof layer, these results were generally as expected although they were not significant enough for graphical presentation therefore only the simulations for heating and cooling are presented here (see Figures 104 and105).

Based on the above discussed results therefore, it is concluded that this scenario is not a desirable design measure for the future development and planning of the city of Beirut due to its overall negative effects on the UHI of the city and therefore overall lowering of thermal comfort levels of Beirut's urban dwellers.

winter day but during the summer day no changes were observed. Finally, heating energy demands were about 6W/m 2 higher when compared against the control run during the winter day but the cooling energy demands were found to fluctuate during the summer day whereby they increased by up to 35W/m 2 at around midday but decreased again by up to 35W/m 2 between the hours of 04:00 to 07:00 and 14:00 to 18:00.

Since some of these differences in results are not so significant, they will not be clearly visible if presented in the form of graphs, therefore for presentation purposes only the simulations results for heating and cooling energy demands are presented here (see Figures 106 and107).

In conclusion therefore, this scenario for increased tree heights seems to have overall positive impacts on alleviation of the UHI effect in Beirut with increased heating energy demands during the winter but mixed impacts on cooling energy demands during the summer which could be because increasing the height of trees to alleviate canyon temperatures is not nearly so effective as increasing the fraction of the trees which is considered in Scenario 6 below. In addition it is worth investigating the costs associated with purchase and planting and maintenance of suitable trees that grow to such heights and that would easily adapt to Beirut's Mediterranean climate not to mention that this approach would require removal and replacement with new tree types which might not necessarily adapt and might require many years for any effects on canyon temperatures to take place. Indeed this mitigation strategy is not found to be feasible for the Beirut context. effects of the increased garden fractions under this scenario while during the summer day cooling energy demands decreased significantly by about 40W/m 2 mainly between the hours of 04:00 and 07:00 and 14:00 and 18:00.

Again, as for the previous scenarios three scenarios, since results will not appear so significant in graphical presentations, the simulations for heating and cooling energy demands are only presented here which show a small yet positive difference in energy demands under this scenario especially during the summer season (see Figures 108 and109).

Therefore, simulation results were generally as expected, with an overall decrease in canyon temperatures, internal building temperatures, and cooling energy demands of the city. The small significance in the output results however is seen later in the discussion section to be because of the lower sensitivity of the TEB modeling scheme to variations in cover fractions as compared to the radiative properties of urban surfaces for example (see Chapter 8). In general however the results were desirable and more suitable for the Beirut context than Scenario 5 and therefore this scenario is considered to be a feasible mitigation strategy for the future sustainable urban planning of Beirut. It is worth noting however that while this scenario might prove to be a very attractive solution for

the Beirut case indeed it may cause undesirable effects in increasing traffic congestions, which accordingly brings to attention the dire need to improve the existing public transportation system of Beirut which is discussed in later chapters (see Chapter 8 34 ).

34 While this research does not aim to find solutions for a more sustainable transportation networking system for Beirut it does bring to attention the important need to consider this recommendation for future sustainable planning solutions for the city

Summary of developing scenarios results for Beirut

Out of the six scenarios analyzed for the Beirut case, it was found that Scenario 1 with increased roof albedos had the most significant effect on alleviation of canyon temperatures. Scenario 2 with increased road albedos also increased canyon temperatures but had generally undesirable effects on internal building temperatures which accordingly increased cooling energy demands. Scenario 3 with increased glass ratio of buildings and Scenario 4 with elevated building heights both increased canyon temperatures and cooling energy demand and therefore gave undesirable results. Scenario 5 with increased tree heights resulted in cooler canyon temperatures. Finally Scenario 6 with increased garden fractions across also had a positive cooling impact on canyon temperatures and was indeed found to be more suitable than Scenario 5 for implementation for the Beirut context as this approach could be regarded as a continuation and expansion of the existing garden fraction while the latter would require replacement and adaptation of new tree types. Based on the simulation results it is concluded that the most suitable UHI mitigating solutions for the Beirut context are Scenarios 1 and 6. This final part of this thesis is divided into three chapters as follows: 1) discussion of the simulation results of the numerical analysis carried out on TEB for the Beirut case;

2) discussion of the achievement of objectives of this research; and 3) the conclusions and the contributions this research makes to the field of urban microclimatic studies in Beirut.

Chapter 8: Discussion

This chapter provides a summary outline of the methodology adopted to investigate the UHI in Beirut, and discusses the outcome of the numerical analysis results, and their significance and meaning.

Overview of Research Methodology

The aim of this research is to determine the nature of the existing urban characteristics of Beirut that have the most significant impact on the UHI of the city. As such, the Town Energy Balance (TEB) urban surface exchange modeling scheme [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF], which is a single layer urban canyon model used for mesoscale studies, is selected to carry out simulations of the urban climate in Beirut. TEB is chosen, out of a choice of 9 potential models considered and assessed for the purpose of this research, due mainly to its successful application for large-scale studies of the UHI at the city-scale and due to the nature of the data required to run the simulations which are possible to obtain and extrapolate for the Beirut case.

Discussion of Numerical Analysis Results

Analysis of the collected data confirms that the city of Beirut is characterized by a predominantly dense urban fabric with over 80% of the land cover being occupied by impermeable buildings and roads and with less than 20% being covered by garden or green areas although these are mostly scattered across the city. The TEB numerical simulation results for the control run reflect the strong impact of the dominating and commonly used artificial urban surface materials on UHI particularly in the high density urban fabrics of Beirut. Canyon temperatures are higher in these latter areas as compared to higher garden fraction areas like Horsch Beirut and AUB areas, both during the winter and summer seasons although the cooling effect of the gardens is more apparent during the summer season. Thus, the importance of gardens in alleviating urban temperatures is made apparent from these simulation results under the control run.

Six scenarios are subsequently devised which are compared against the control run data. The purpose of this exercise is to find the most suitable UHI mitigation strategy within the urban planning and design disciplines for the city. Below is a discussion of the output results for these scenarios as follows:

Scenario 1

For Scenario 1, the strong impact of the low albedo (α) or solar reflectance of the commonly used concrete roofing surfaces is made apparent when the solar reflectance or albedo of concrete is raised from 0.2 to 0.7 and compared against the control run data.

Simulation results show generally lower street canyon temperatures and significantly lower roof temperatures as well as lower cooling energy demands during the summer but higher heating energy demands during the winter especially in the dense urban fabrics of the city. Although this scenario results in a higher heating energy demand by about 11W/m 2 during the winter when compared to the control run simulations, which is not a desirable result under this scenario, it is seen that indeed these are offset by the lower cooling energy demands of about 50W/m 2 during the summer, which is almost five times more than the heating energy loss, thus rendering this heating loss as negligible.

Therefore results show that Scenario 1 is a feasible mitigation strategy for the UHI in Beirut and can indeed be implemented for Beirut city by painting roofs with white coloured coatings or limestone for example but this will be discussed in more detail in later sections.

Scenario 2

For Scenario 2, the solar reflectance of road surfaces is raised from 0.225 to 0.8 and upon comparison with the control run data it is found that the temperatures of road surface and canyon temperatures are lowered. On the other hand, the temperature of facades, roofs and internal building temperatures are raised. These results can be attributed to the higher reflective properties of the road surfaces and the resulting increases in radiative exchanges that accordingly take place predominantly between the roads and walls of the buildings accordingly affecting their temperatures. Hence, the cooling energy demands are raised during the summer due to the warmer wall temperatures while during the winter the heating energy demands are lowered. Therefore, while Scenario 2 might have significant cooling impacts on road surface temperatures, the overall effect on walls and internal building temperatures are undesirable resulting in increased cooling energy demands during the summer season and therefore higher gas emissions thus exacerbating the UHI effect in the street canyons of Beirut even further.

Selection of this scenario is therefore not a suitable mitigation strategy for Beirut.

Scenario 3

Under Scenario 3, which involves raising the percentage of the glass ratio of buildings, it is confirmed that such a scenario exacerbates the UHI effect but especially during the summer season during peak hours of incoming shortwave solar radiation between the hours 11:00 and 14:00 hrs. All output results under Scenario 3 show a tendency to increase urban surface temperatures and accordingly impact the heating and cooling energy demands of buildings. Therefore Scenario 3 confirms that increasing the glass ratio of buildings is not a sustainable architectural approach for new buildings designs especially due to their significant effect on canyon temperatures thus reducing thermal comfort levels of city dwellers.

Scenario 4

As for the modification of building heights from 15 to 35m under Scenario 4, simulations show a resulting increase in canyon temperatures during both the winter and summer seasons. Taller buildings reduce the sky view factor, and reflect the incoming solar radiation to the walls of the buildings thus preventing outgoing long-wave radiation from escaping into the atmosphere. Thus the radiative exchanges occur mostly between the roads and facades of the buildings in the street canyon accordingly raising canyon temperatures. Of course the angle of the sun over the horizon also contributes to the intensity of the solar radiation that is received over urban surfaces which also affects canyon temperatures. The results are therefore more significant during the summer as compared to the winter (see Figure 110) which is why it is important to find sustainable mitigation solutions to alleviate these UHI effects especially during this time of the year.

Regarding other output results therefore, under Scenario 4, the simulations for surface road temperatures also increased during the winter season as expected and also during the summer season. Surface roof temperatures under this scenario decreased, since with increased building heights and a reduced sky view factor, most of the radiative exchanges for the incoming short-wave solar radiation take place between the roads and walls of the building. Wall temperatures also increased during the winter and summer seasons as expected due to the higher radiative exchanges that take place between roads and facades as a result of the lower sky view factor. Internal building temperatures also increased during both winter and summer seasons under this scenario as expected due to the reduced sky view factors. Finally, heating energy demands decreased slightly during the winter season while the cooling energy demands increased during the summer as expected. Therefore, this scenario showed the major disadvantage in constructing higher buildings in Beirut due to their undesirable effects in raising canyon temperatures and cooling energy demands thus lowering the thermal comfort levels for urban dwellers.

Having said this, there is limited available space for new buildings constructions and given the increasing demand for real estate all over Beirut, developers and architects alike are finding that the best solution to maximize space and meet the real estate demand is to increase the height of building but unfortunately this is having significantly negative effects on the UHI of the city as seen in the simulation results in this scenario. Concerning scenario 5, where the height of high vegetation or trees is increased, canyon temperatures results decreased slightly during both winter and summer seasons and this can be attributed to the increased shading and consequent cooling effect of trees via evapotranspiration on buildings and corresponding canyon temperatures. Road, roof, and wall temperatures were lowered as well as internal building temperatures under this scenario. Consequently, the heating and cooling energy demands were affected as expected. Although in general this scenario shows overall cooling tendencies, it is not considered to be a very feasible solution for the Beirut context mainly due to the difficulty in finding the appropriate vegetation types of heights greater than 25m

(whereas the height of native trees reaches up to about 10m) that could easily acclimatize to Beirut weather conditions and which may potentially take years to show positive effects on canyon temperatures after removal of existing trees and replanting.

Scenario 6

Finally, in the case of modification of the garden fraction under Scenario 6, which is increased by the same fraction by which the road fraction is decreased (50%), the output results show a tendency to decrease canyon temperatures, road, roof and wall temperatures, and internal building temperatures during both winter and summer seasons.

The cooling and heating energy demands are also consequently affected with lower cooling demands during the summer (40W/m 2 ) but higher heating demands during the winter (7W/m 2 ) when compared against the control run simulations. Again as for Scenario 1, while the latter is not a desirable result of this scenario it is seen that the energy savings during the summer is almost six times more than the heating energy loss during the winter thus making this loss negligible. Moreover, it is worth nothing, that the effects under Scenario 6 are not as significant as they are for Scenario 1 for example under which the solar reflectance property of roof surfaces is increased. In fact, according to [START_REF] Lemonsu | Modeling of the surface energy balance of the core of an old Mediterranean city: Marseille[END_REF], the impact of variations of the cover fractions on the fluxes computed by TEB is not very important and is always under 6W/m 2 as seen in the case of the simulation results under this scenario 6 although they were somewhat higher for the Beirut context (up to 35W/m 2 ). Therefore, due to the generally favourable results of the simulations, Scenario 6 is recommended as a suitable mitigation strategy for the Beirut case and is in fact considered to be an important step toward achieving more suitable thermal conditions for urban dwellers, with increased energy savings in Beirut especially during the summer season not to mention the many other aesthetic benefits of implementing a bigger fraction of urban trees and vegetation around the city. However, it is worth noting while this scenario is a promising solution for Beirut, it will essentially increase traffic congestions around the city due to the reduced road fractions. This therefore brings to attention the important need to improve the existing public transportation of the city, which is quite poor in its existing state as private cars far surpass public transport, with implementation of for example dedicated bus lanes, and even railroads or tramways which were in fact operational in Beirut from the time of the Ottoman rule, and during the French mandate, up until the 1960s. These tramway tracks have unfortunately been covered by layers of asphalt material therefore in the event where operation of tramways is indeed considered in future sustainable planning scenarios for Beirut, tramway tracks will have to be reconstructed. Therefore, this scenario has to be strategically planned by urban planners, transportation and landscaping engineers and architects to maximize the cooling effect of the city of Beirut under this specific scenario which is indeed a promising solution for the city.

Table 28 is a summary of the results of the 6 scenarios devised for the purpose of this research and the respective determination of their suitability for the Beirut context. Increasing the garden fraction and reducing the road fraction resulted in cooling of canyon temperatures and lowering of overall cooling energy demands. This strategy was found to be more suitable than Scenario 5 as it is considered to be a continuation and expansion of the existing situation using similar tree types that have already adapted to Beirut's Mediterranean climate. However this scenario may have potentially negative effects on the traffic congestions. It will therefore be necessary to address the improvement of the public transportation of the city with implementation of dedicated bus lanes and even operation of tramways. It requires strong coordination between urban, transportation and landscape planners for successful results-> suitable mitigation strategy for Beirut Chapter 9: Achieving Research Objectives

Based on the numerical analysis results of this research, the five key objectives initially outlined in the introductory chapter of this thesis are accordingly discussed in this chapter to assess whether and how this research was successful in achieving these objectives for the Beirut context.

To measure and model the effect of UHI in Beirut and identify major contributing factors

The first objective of this research was to determine whether it would be possible to measure and model the effects of the UHI in Beirut. To measure directly the effect of UHI in Beirut it would have been necessary to select and obtain relevant measurement equipment from abroad, as they are not available in the country, and which are not only costly and time consuming to ship but also require special permits from the relevant authorities. Considering the unstable situation of the country this attempt would have been futile not to mention time-consuming. Hence, climatic records from the AUB old observatory station were obtained to investigate historical climatic trends in Beirut.

As for modeling of UHI across Beirut, it was first necessary to identify the most suitable modeling scheme for the Beirut context. Out of a choice of nine possible modeling tools in the available literature, including numerical and empirical models developed by [START_REF] Martilli | An urban surface exchange parameterization for mesoscale models[END_REF], and [START_REF] Kusaka | A simple single-layer urban canopy model for atmospheric models: comparison with multi-layer and slab models[END_REF] for example, and after application of several criteria to assess the suitability of these models for the Beirut context, including nature of data and scale at which these models are used, the Town Energy Balance (TEB) urban surface exchange numerical model [START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] was selected. TEB was therefore selected because it requires the least detailed data entry while still making it possible to carry out accurate parameterization of the atmosphere and surface energy exchanges as validated in numerous studies in this regard for other similar dense cities. In addition, TEB is applied largely for mesoscale studies of the UHI and with successful results [START_REF] Lemonsu | Modeling of the surface energy balance of the core of an old Mediterranean city: Marseille[END_REF][START_REF] Masson | Evaluation of the Town Energy Balance (TEB) scheme with direct measurements from dry districts in two cities[END_REF][START_REF] Masson | Urban surface modeling and the meso-scale impact of cities[END_REF].

Therefore, considering that TEB is the most adequate tool to conduct UHI simulations for large scale studies, and considering that TEB does not require data for individual buildings in the city, which is advantageous when considering that data of this nature is limited in Beirut, TEB was found to be the most suitable of the nine modeling schemes considered for the Beirut case.

As such, by using the TEB urban surface exchange modeling scheme, and by using forcing climatic records from Fanar weather station, it was possible to run simulations across the entire administrative area of Beirut for twelve consecutive months for the year 2009 to simulate temperature differences and accordingly impacts on UHI across varying town cover surfaces of Beirut. While >80% of the city is characterized as dense to medium density urban fabric, through TEB, it was possible to identify the major contributing factors of UHI in Beirut (Kaloustian & Diab, 2015).

Therefore, while direct measurements of UHI were not possible, modeling of the UHI using TEB modeling scheme was, giving realistic and justifiable results which were consistent with current studies. Indeed, the scientific findings of this research confirmed that TEB is a very important decision-making tool and can be used as a means to promote evidence-based planning and design practices in Beirut, which is a new trend in urban planning and design disciplines where designers and planners use tangible facts about the environment in order to design more sustainable and healthier environments for cities [START_REF] Faludi | Introducing evidence-based planning[END_REF]. It therefore involves integration of the best possible research evidence with design and planning experiences as well as knowledge of the needs of the target populations whereby surveys and/or scientific findings or evidence become part of the classic planning traditions [START_REF] Davoudi | Evidence-based planning: rhetoric and reality[END_REF][START_REF] Faludi | Introducing evidence-based planning[END_REF]. Indeed, according to [START_REF] Krizek | Is there a role for evidence-based practice in urban planning and policy?[END_REF] there is a valuable role for research-generated evidence to inform decision-making. This recommended approach is discussed in more detail in subsequent sections.

The flow chart in Figure 111 The second objective of this research was to assess whether urban microclimatic issues are considered in the urban planning processes for Beirut/Lebanon. To this end therefore it was necessary to review the history of urban planning practices to present day as well as the legal documents of relevance in this regard. This section therefore investigates the extent to which the environment is considered in the Urban Planning Law, the Building Code and the zoning of Beirut whereby the two former legal documents include designs and policies at the national scale and not specifically at the city scale of Beirut. While it would be useful to also investigate any policies associated with transportation and infrastructure design and networks, it is important to note that this research focuses its investigations primarily on the effects of the existing urban geometric characteristics on the UHI of the city, which therefore includes building heights, building construction materials, building glass fractions, thermal and radiative properties of construction materials as well as garden fractions. To this end, assessment in this research is restricted to the aforementioned legal policies and zonings as they pertain to their impacts specifically on the urban climate.

As such, as previously mentioned, the key parties involved in the urban planning process in Lebanon, and more specifically for the Beirut case study area, include the Municipality of Beirut, the Directorate General of Urban Planning (DGUP), the Higher Council of Urban Planning (HCUP), the Regional Departments of Urban Planning, and the Order of Engineers and Architects and so on (see Chapter 5). These aforementioned parties are therefore responsible for all issues pertaining to management of the urban Although drafted and approved during a time of great civil unrest, the Urban Planning Law #69 does in fact consider the environmental dimension to a certain extent in 8 of its directives as discussed previously (Chapter 5) and as highlighted again in Regarding the urban zoning specifications the city of Beirut is divided into 10 zones, where each zone has specific zoning requirements for land subdivisions, surface areas permissible for construction in the plots, allowable height for buildings, and so on.

Within the urban planning process for Beirut, the zoning specifications do not take into consideration the environmental dimension but rather focus more on the building specifications themselves depending on their respective zones. Having said this the building height is an important factor in terms of its potentially significant impacts on the UHI of a city whereby the taller the building the more significant the reduction in the sky view factor with more heat being trapped in the canyons thus elevating street temperatures and the UHI and this factor is indeed investigated in this research (see Chapter 7 and subsequent sections). As for the Building Code #646, this does include some obvious green elements such as planting trees, ventilation of specific areas of buildings that do not have a view (window/air passage), and it encourages installation of solar hot-water systems for all house owners.

Moreover, the National Physical Master Plan of the Lebanese Territory (NPMPLT) or SDATL, which was issued as a decree in the year 2009, is one of the first official urban planning documents, which emphasizes the importance of considering the environmental dimension but it should be emphasized that this is a master plan at the national scale and not for the city scale per se and therefore has a more general approach toward recommending measures to protect the environment. More detailed works are accordingly required to find recommendations more specific to the city scale (mesoscale) of Beirut case study area, which is one of the objectives of this research. Also, Solidere, although a private company, is taking major steps to implement environment and microclimatic factors in its urban planning and architectural designs although these are focused only in the BCD area which is owned by Solidere. In addressing the second objective of this research therefore, it is concluded that throughout its history, some important achievements have been made to consider the environmental dimension but mainly at the national level and not the city scale or mesoscale level of Beirut case study area. However, these environmental issues are not rigorously implemented within the urban planning processes [START_REF] Fawaz | Urban planning in Lebanon[END_REF] MOE/UNDP/ECODIT, 2011). These can be achieved by improving and strengthening (2004) This code does include some obvious green elements such as planting trees, ventilation of specific areas of buildings that do not have a view (window/air passage), and it suggests installation of a solar hot-water system for house owners but it is not regimentally applied by the concerned professionals in the field, including architects and engineers, since it does not allow for flexibility in design. Urban zoning of Beirut (Ecochard) (1963) This divides Beirut into 10 zones and focuses more on the building specifications themselves depending on their respective zones as opposed to any environmental considerations. NPMPLT -Decree No. 2366(2009) The NPMPLT emphasizes the importance of considering the environmental dimension in the master planning of the country, and not at the city scale, requiring therefore more detailed goals and objectives Institutional framework Concerned authorities are generally understaffed and/or do not have skilled personnel; this is typical in governing agencies across Lebanon and is primarily due to low associated salaries.

Solidere

The private company of Solidere is involved in important urban planning and design works in Beirut Central District implementing sustainable and environmentally friendly practices that take into consideration the urban microclimate such as soft landscaping and environmentally friendly green building designs and planning. Thermal standards for buildings across Lebanon (2005) Thermal standards for buildings were established for Lebanon based on their climatic zones where Beirut falls within the coastal climatic zone but these standards have not yet been approved or adapted. Energy Efficiency building code road map (2012) An energy efficiency building code road map was also established for Lebanon by

To find most suitable measures to alleviate the effects of UHI in Beirut from a technical perspective

Since urban planning is a technical and political process concerned with the use of land and design of the urban environment, including buildings, water and energy and transportation infrastructures, the process to alleviate the impacts of the UHI effect can be devised by targeting one or more of these branches of the urban planning discipline, both from a technical and political approach. For proposed technical solutions to take effect it would be necessary to ensure support from a legal and political perspective.

As such, from a technical perspective, this research was able to achieve its third objective which involved the determination of the most suitable measures to alleviate the effects of UHI of Beirut. Again it is important to emphasize that this research focused primarily on technical solutions from the perspective of the urban design and geometry of the city while transportation and infrastructure dimensions were not included. Indeed, the TEB simulation results for the devised scenarios helped identify and provide the evidence for the urban parameters that play the most significant role in exacerbating the UHI effect in Beirut, namely the low solar reflectance properties of roofs and the low percentage of garden fractions spread out across Beirut. This research therefore recommends replacing existing roofing materials with cooler building materials, either by coating existing roofs with white-coloured paints or by spreading limestone layers across the rooftops. Existing roofing materials have a low α value of 0.2. Research shows that cool roofs and/or white roofs save 10%-20% airconditioning for an area under roofs therefore resulting in significant cooling energy savings [START_REF] Akbari | Rapid development of global heat island mitigation studies and countermeasures: a 30 year success story[END_REF] (see Figure 112). Moreover, a materials measurement performance tests for roofs show that upon testing and comparing the surface temperature of varying roofing materials over a course of four days (26-29 August 2004), cool white roofs have the lowest surface temperatures, at around 30 o C, as compared to concrete roofs, at about 45 o C (see Figure 113). According to [START_REF] Synnefa | Experimental and numerical assessment of the impact of increased roof reflectance on a school building in Athens[END_REF], increasing either reflectance and/or emittance lowers a surface's temperature and contributes to the decrease in temperature of the ambient air as the heat convection intensity from a cooler surface is lower. In fact, under peak solar conditions (about 1000W/m 2 ) the temperature of a black surface with solar reflectance of 0.05 is about 50 o C higher than ambient air temperature. For a white surface however with a higher solar reflectance of 0.8, the temperature rise is only about 10 o C. Therefore, among heat island mitigation strategies, the use of cool materials has gained a lot of interest due to their efficiency, low-cost and easy to apply solution (Akbarai et al., 2001;[START_REF] Doulos | Passive cooling of outdoor urban spaces. The role of materials[END_REF][START_REF] Rosenfeld | Mitigation of urban heat islands: materials, utility programs, updates[END_REF][START_REF] Rosenfeld | Cool communities: strategies for heat island mitigation and smog reduction[END_REF][START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF], Santamouris et al., 2012). To ensure implementation of this strategy however it would be necessary to coordinate with architectural and engineering sectors under the Order of Engineers and Architects (OEA) for example but this is addressed in more detail in the fourth objective of this research in the following section. This research also recommends increasing the percentage of vegetative surfaces.

According to the available literature, trees and green spaces contribute significantly to cooling cities and saving energy [START_REF] Santamouris | Energy and Climate in the Urban Built Environment[END_REF]. Shade trees intercept sunlight before it warms a building while the urban forest cools the air by evapotranspiration.

Trees also decrease the wind speed under their canopy and shield buildings from cold winter breezes [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF]. Evapotranspiration is the major mechanism through which trees contribute to decreasing urban temperatures. Trees also help mitigate the greenhouse effect, filter pollutants, mask noise, prevent erosion and have a calming effect on people [START_REF] Santamouris | Energy and Climate in the Urban Built Environment[END_REF]. They also improve quality of life, increase value of properties, decrease rain run-off water and hence also protect against floods (McPherson et al., 1994). The effectiveness of vegetation in an urban area depends on its intensity, shape, dimensions and placement. But in general, any tree, even one bereft of leaves, can have a noticeable impact on energy use [START_REF] Akbari | The impact of trees and white surfaces on residential heating and cooling energy use in four Canadian cities[END_REF]. However, a study on the measurements of the ambient temperature in and around an urban area in Athens, Greece showed that upon leaving the park an immediate temperature increase of about 1K occurred showing that there is no constant gradient of temperature increase with distance from the park but rather a step function [START_REF] Santamouris | Energy and Climate in the Urban Built Environment[END_REF] thus reflecting the very localized effect of urban trees and vegetation on ambient temperatures as opposed to a wider effect at the city scale. In fact, the control run results for canyon temperature simulations across the entire city of Beirut showed that just outside of the boundaries of the pine tree garden of Horsch Beirut in Mazraa, in the south of Beirut for example, the temperatures immediately shoot up again from around 38 to 42 o C. Having said this, according to TEB simulation results, there are some overall energy savings during the summer season thus highlighting the more significant shading effect of trees on buildings. Numerous studies show the substantial energy savings due to planting of shade trees or urban forests [START_REF] Rosenfeld | Cool communities: strategies for heat island mitigation and smog reduction[END_REF][START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF]Rosenfeld, Santamouris, 2013).Therefore existing literature highlights the successful results upon implementation of this mitigation measure resulting in alleviation of UHI effects and energy savings [START_REF] Akbari | Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas[END_REF][START_REF] Oliveira | The cooling effect of green spaces as a contribution to the mitigation of urban heat: A case study in Lisbon[END_REF][START_REF] Rosenfeld | Cool communities: strategies for heat island mitigation and smog reduction[END_REF]. As for the case of the first recommended mitigation strategy, it is necessary to ensure implementation by communicating and coordinating with all concerned urban planning authorities. The evidence provided by the TEB modeling tool in this research can be used to facilitate this communication process and this is addressed in the fourth objective of this research in the subsequent section.

Therefore, the third objective of the thesis was achieved in this research whereby the most suitable technical measures for mitigation of the UHI for the Beirut context were determined and accordingly recommended based upon the simulation results of the devised scenarios on TEB. For the recommendation to raise the solar reflectivity of rooftops, this could easily and successfully be achieved by applying white coatings of paint on the rooftops of existing as well as new buildings in Beirut. The second recommendation on the other hand, to increase the fraction of urban gardens and vegetation, can be considered to be an optimistic scenario, although it could essentially be achieved by ensuring close coordination and communication between and amongst all relevant authorities and by selecting for example pilot areas in which to test the success of this mitigation strategy for the Beirut context. The present condition of roads may also need to be considered which may not have enough pavement or median spaces to plant vegetation, in which case such sections may need to be eliminated with more focus on increasing the solar reflectivity of the rooftops here, although it would be interesting to conduct a study to investigate the total length of such roads in Beirut which could help in determining the suitability of this proposed scenario. On the other hand, those roads with sufficient pavement spaces could be the focus of attention for tree or vegetation planting in Beirut. In addition, the sufficiency of water supplies to maintain increased garden fractions across Beirut would also need to be considered if one is to ensure the success of such a scenario. In this case it is important to emphasize that although Lebanon is rich in water resources there is the concerning problem of sustainable management of water resources in the country. Having said this, the national water strategy of Lebanon (Ministry of Energy and Water, 2010) is the gateway to ensure sustainable water supply to all areas of Lebanon including Beirut through the construction of dams and reservoirs that can also help to ensure successful implementation of this scheme for Beirut.

Specifically for Beirut, it has been proposed to construct the "Bisri Dam", which has a capacity of 125 million cubic meters to supply water to approximately 1.8 million inhabitants residing in Beirut and Greater Beirut Area (www.cdr.gov.lb). Therefore, according to the simulation results from TEB, significant positive steps will be taken to alleviate the impacts of UHI in Beirut city.

To assess implications for urban planning process from an institutional and administrative perspective

The previous objective of this research was achieved whereby technical solutions to alleviate the effects of the UHI for the Beirut context were found based on the numerical analysis results of the devised scenarios using TEB. However, this in itself is not enough to ensure proactive implementation and successful results across Beirut.

Coordinated efforts from the responsible authorities are necessary to ensure implementation of the scientific findings of this research for improvements in planning and design practices in Beirut and accordingly mitigation of the UHI impacts. Indeed this could be managed by the potential establishment of a council or agency that could deal solely with urban climatic issues and that could include one member from each of the concerned stakeholders and that could be under the responsibility of the Ministry of Public Works or Transport of the Ministry of Environment. In addition, the evidencebased planning approach could be implemented for successful application of the recommended mitigating actions.

As previously mentioned evidence-based planning is a new approach in the planning and design sectors that is being implemented nowadays in decision-making processes. Evidence contributes to the sustainable development of a city acting as a common language that facilitates communication between the various involved parties thus tying the measurement process more closely to planning. Unfortunately, in Lebanon, urban planners and architects have little or no knowledge of the urban microclimate and the impact of urban planning and urban design parameters on the UHI and this is due mainly to little or no climatic information awareness. In addition, there is no existing legislation or code that can at a minimum provide guidance in this regard, be it at national scale or city scale, as discussed in the second objective of this research. There is therefore a need for systematic dissemination of climatic information by providing evidence to urban planners and designers which can accordingly help in promoting informed decision-making.

There are also authorities and parties worth mentioning that are already involved in this field in Lebanon such as the climatic department of the MOE (http://climatechange.moe.gov.lb/home) and which can therefore be a great source of knowledge for topics associated with the climate in Beirut. The Lebanese Center for Energy Conservation (LCEC) is another national organization affiliated to the Lebanese Ministry of Energy and Water (MOEW) and which addresses end-use energy conservation and renewable energy at the national level (www.lcecp.org.lb). The LCEC could therefore also provide knowledge on urban design parameters and buildings designs for example to help minimize exacerbation of the UHI as well as adaptation measures. Indeed the LCEC was recently involved in a very important energy-savings campaign whereby it provided incentives through subsidies to homeowners to implement solar water heating which achieved successful results across the city of Beirut (see LCEC webpage).

LIBNOR or the Lebanese Standards Institution is another important authority attached to the Ministry of Industry (MOI) that is involved in preparing national standards for structural codes for buildings, amongst others, and could therefore be another very useful source of knowledge in the communication network that is proposed in this research (www.libnor.gov.lb). Moreover, the Lebanon Green Building Council or

LGBC (www.lebanon-gbc.org), which is a Non-Governmental Organization (NGO), is another source of climatic knowledge which provides incentives for a variety of relevant parties, including consulting engineers, architects, building contractors, real estate owners and promoters, manufacturers, educational institutes, and research organizations, by offering a Lebanese certification system for buildings, known as "Arz", that adopt environmental parameters and transform the way buildings and communities are designed into a prosperous environment that improves the quality of life (www.arzrating.com).

Currently, LGBC is not involved as a stakeholder in urban planning decisions and could indeed prove to be a very useful source of knowledge in decision-making processes in this regard. Finally, academic researchers in the field could also be involved in this process of transferring urban climatic knowledge. However, it is also important to emphasize that there should be robust and continuous implementation of the knowledge and/or evidence that has been gained through TEB in all future urban plans and designs of the city. In order to achieve this it is recommended that all relevant parties employ properly skilled, certified and trained staff that can carry this through and ensure best practice at all times.

Therefore, the successful communication between and amongst these parties and the urban planning authority would be an essential first step toward mitigating the UHI in Beirut and this could be achieved by first establishing an urban climate agency at the city scale, by strengthening the existing institutional framework (see Figure 114) and finally by ensuring support through the evidence-based planning approach through integration of the scientific findings, by TEB, into each stage of the decision-making processes (see Figure 115). As previously discussed, the existing Urban Planning Law #69 considers protection of the overall environment and natural landscapes within 8 of its directives.

There is however a gap in the existing legislation with respect to the need to consider climatic issues in urban planning schemes. Therefore there is an opportunity for modification and amendment of this Urban Planning Law #69 to take into account the climatic dimension however it is important to note that any modifications made to the UP law can only be at the large-scale where more detailed specifications could be provided at building scale in the Building Code for example which is discussed next. In addition, any recommendations are restricted specifically to urban geometric and design parameters and do not include transportation and infrastructure sectors. Table 30 therefore recommends improvement of the Urban Planning Law #69 to consider more rigorously protection of the urban microclimate at the national scale.

Indeed there is also a gap in the consideration of "green" initiatives in the existing Building Code #646 (or construction law) for Lebanon thus again there exists an opportunity for modification of building design codes to reflect green building designs which could be more specific to meso-scale. Sustainable design is fast becoming the norm for architects around the world accelerated by the advent of green building rating Dhabi for example it is found that it is not just a rating method but it is a vision and a desire to achieve a new sustainable way of life in the Emirate. The reason why Estidama is so successful in Abu Dhabi is because of the large awareness and educational campaigns carried out for all developers, engineers, architects and urban planners to think and act in a sustainable manner. However, these are all voluntary programs similar to the previously mentioned "Arz" building rating system for Lebanon the implementation of which is encouraged by the Lebanon Green Building Council NGO. A much stronger approach would be required in Lebanon for awareness and incentives in order to achieve successful results similar to the Abu Dhabi case in which case robust implementation of the green building requirements at the building design level for the Beirut case is recommended. However, the question of how to go about making this change arises.

Should it first be adopted as a voluntary green code program to allow adequate time for all concerned parties to become educated and more familiar with it, or should the green code be adopted as mandatory as a way to achieve environmental benefits on a largescale? In the case of the latter, those who are familiar with sustainable design practices would experience an easy transitional phase but others would need to pay more attention to the building performance measures to ensure code compliance while a few others might perceive this as a dramatic change (Building Energy Forum, 2012). In addition, a new green building code would potentially mean new training requirements for architects and engineers alike that would essentially incorporate another layer of expertise on the fundamentals of environment and climate that form the basis of the licensed practice.

Having said this it is worth noting that writing codes that apply with equal rationale to a variety of building types in different geographic locals and climatic zones is difficult which is why it would be necessary to establish building codes that target the respective climatic zones in which they lie. Thus, for the case of Beirut city, this would fall under the coastal climatic zone.

Assuming that the choice for modification of the existing Building Code #646 of Lebanon is made therefore, it would accordingly be necessary to implement requirements for these green building elements, such as the need for cooler materials for rooftops of buildings including white-coated paintings or limestone which could be spread out across the entire roof area of a building. These are common methods that are being practiced in many similar dense cities experiencing the undesirable effects of UHI [START_REF] Akbari | Rapid development of global heat island mitigation studies and countermeasures: a 30 year success story[END_REF].

Therefore it is recommended to improve the existing Building Code #646 to include an additional section listing the requirements for green buildings in Beirut under which the general criteria outlined in Table 31 below could be added.

Opportunities also exist for the modification of zoning specifications to specify for example surface area requirements for green surfaces within building plots, or to revise height requirements for buildings within each zone as not all the zones have specifications for building height, namely zones 4, 5, 6 and 7. Given the numerous high rises spreading across the city of Beirut like the Marina Tower35 in Ain El Mreisseh and the Sama Tower36 in Ashrafiyeh (see Figure 116 below), implications on the UHI can be quite significant as seen in Scenario 4 of this research (see Chapter 7). Once the specifications have been made, stringent measures would be necessary from the side of the planning authorities to forbid the issuance of building permits unless they meet the specifications as per the modified "sustainable or green" zoning plan. Should this requirement not be met due to limited space availability or otherwise, there should be a requirement for the implementation of cool building materials, higher fraction of green surfaces, low glass ratio and so on before permits are finalized. These should be specified prior to construction otherwise no construction is permissible. Nonconstruction zones can also be determined

As there are no agricultural lands within Beirut and as most of the land is already built-up, this directive does not apply for the Beirut case therefore there are no perceived opportunities here. 9 Zones that have not been planned can be placed under study for a period of up to two years further to a decision made by the Ministry of Public Works and Transport (MOPWT), and after consultation with the HCUP and the relevant municipality. During these two years however no construction is to be permitted. Forested areas are not allowed to be destroyed and the natural landscape of the area should not be changed All zones within the Beirut administrative area are planned.

There is no longer any remaining natural landscape within the boundaries of Beirut. In Beirut there is the Horsch Beirut public garden which is comprised of pine trees and was created as an urban park in the early 2000s. Therefore this specific article could be elaborated to say that all existing urban gardens should also not be changed especially due to the positive role they play in alleviating the urban microclimate.

17

No monetary compensations will be provided for any changes to building coefficients including setbacks, This directive could be elaborated to mention the important role the specified building parameters play number of floors, building height, and colour, which play an important role in protecting public health and safety and the natural environment.

not only in protecting public health and safety and the natural environment but also the urban climate. Relevant authorities may expropriate private land for the benefit of the public good by compensating the respective landowner(s) with a nearby land of equal value.

The expropriation of private land for the benefit of the public good could be further to elaborated to include examples of such types of public good particularly where they relate to the incorporation of urban parks for example since these are not only aesthetically pleasing but also help improve the urban microclimate thus improving the overall quality of life therefore benefiting the public good. Relevant authorities may carry out re-parceling of previously zoned areas in order to facilitate urban planning.

Again this specific article is beneficial especially if the relevant authorities are planning to re-parcel to incorporate green areas in their newly zoned areas. An opportunity exists here in that this article could be further elaborated to express that it is not only to facilitate urban planning but sustainable urban planning which would again benefit the public good Government or relevant municipality may ask the landowners of residential areas nearby forested areas or natural open spaces to swap their land with another piece of land.

Again there is another opportunity here in that this article could be further elaborated to express the need for the government or relevant municipality to protect these forested or natural open spaces especially due to the role they play in cooling urban microclimates and improving the overall quality of life. Municipalities or union of municipalities can agree with landowners of forest or natural sites to open these areas as public areas or parks and municipalities can accordingly charge admission fees for maintenance or upkeep An opportunity exists here whereby this article could also mention the importance of ensuring maintenance and upkeep especially due to the significant role they play in improving quality of life and the urban climate. In conclusion therefore, it is found that there are indeed opportunities for improvement of urban planning and design policies or codes in Lebanon for better consideration of the urban microclimatic issues at national scale and accordingly cityscale.

Chapter 10: Conclusion

Urban areas tend to have warmer air temperatures than their rural counterparts as a result of gradual land surface modifications that include replacing natural vegetation with buildings and roads. The urban heat island or UHI which describes this phenomenon arises mainly as a result of the higher solar absorptive capacity of the artificial urban surfaces that replace the naturally vegetated surfaces, which accordingly become extremely hot, thus warming the surrounding air. This is cause for concern especially where the thermal comfort level and well-being of urban dwellers is concerned, not to mention the strong link that exists between heat stress and mortality as seen in the case of the Paris heat wave of 2003, for example, which was responsible for the death of thousands of urban residents. The issue of urban climate and more particularly urban heat island is part of the more general subject of adapting to climate change impacts. Local communities are showing an increasing demand for knowledge on the impacts but also on the means of available local solutions as such. This research had 2 core objectives: 1) to find the main causes of urban planning and building design characteristics that exacerbate the UHI within the context of the densely populated city of Beirut; and, 2) to propose the most suitable mitigating actions from an urban planning and design perspective with the aim of reducing urban warming in Beirut.

For the 1 st objective, simulations were carried out for the existing urban conditions across the entire administrative area of Beirut using the Town Energy Balance or TEB model. This numerical model, which was developed at Météo France, parameterizes the surface-atmospheric energy exchanges at the city scale or meso-scale.

For the 2 nd objective, realistic and feasible mitigating scenarios were devised for the Beirut context and were accordingly run on TEB. The simulation results helped to recommend urban heat island mitigating actions for the urban planning and design sectors in Beirut. This thesis was therefore organized into 5 main sections as follows: 1) introduction and scale of study; 2) literature review and analysis; 3) Beirut context; 4) numerical analysis; 5) discussion and conclusions.

Within a city, the various complex interactions between the existing urban components can have a significant impact on the urban climate, which can be analyzed at various different scales as discussed in the 1 st section of this research. At the micro scale, or what is otherwise known as street-scale, the main physical mechanisms involved in influencing the urban climate include air circulation strongly influenced by evaporation, the contributions of anthropogenic heat, radiative or thermal heat due mainly to the geometry of the city, and the radiative properties of building materials.

All these physical mechanisms at the street scale can lead to the UHI phenomenon at the scale of the city. These are expressed through the radiation balance where all the associated processes are affected by the urban environment because of its geometry, radiative properties of its materials, and air pollution, all of which help to explain the formation of the urban heat island As the 2 nd section details therefore, the city has a rather significant influence on the urban heat island, although it is important to note that the geographical factors and topographic situation of the city (such as mountains, valleys, lowlands, etc.) also play a vital role in this respect.

Other factors that contribute to the formation of the urban heat island as seen in the 2 nd section of this research include:  natural factors: wind speed and intensity of cloud cover, time of year (season) and time of day; and,  anthropogenic factors: increased urbanization and replacement of natural surfaces with artificial surfaces that have typically low albedo or solar reflectivity properties, air polluting emissions from industrial activities, transportation and air-conditioning and domestic heating, and urban geometry that includes heights of buildings, orientations, sky view factor, and height to width ratio of buildings.

Indeed the urban heat island is one of the more noticeable aspects of urban climate. Numerous studies show the various techniques and criteria that are being implemented to measure and reduce urban warming effects. For measurement techniques, some of these include, for example, direct measurements using fixed or mobile traverses, while others include application of either high resolution orthophotography or thermal remote sensing imagery. As for mitigating actions, some of these include implementation of larger fractions of gardens while others include increasing the albedo of urban surfaces, for example. Indeed, for the purpose of this research in the Beirut context, the identification of these various techniques for measurement and mitigation of UHI were deemed important.

In the 3 rd section of this research, an assessment of the existing urban situation within the Beirut context including land cover and land uses, urban zoning, urban morphology, and albedo of dominating artificial surfaces, confirmed that Beirut is an artificial city with a very low percentage of vegetation cover. Indeed >85% of the urban surfaces, namely roofs and roads, have low albedo properties or solar reflectivity. The average height of buildings has also been gradually increasing, especially over this last decade. These urban characteristics of Beirut can all contribute to the exacerbation of the urban heat island phenomenon.

What is interesting and based on the aforementioned findings is the fact that urban policies in Lebanon do not consider or mention protection of the urban climate. An assessment of the legal context in the 3 rd section showed that the Urban Planning Law #69 (dated 1983) and the Building Code #646 (dated 2004) are the two main legal documents that are of utmost relevance within the urban planning and design disciplines for Beirut, although neither mention or provide relevant codes that take into consideration the urban climate. Additionally, the National Physical Master Plan of the Lebanese Territory (NPMLT) or the Schéma Directeur d'Aménagement du Territoire Libanais" (SDATL) (prepared in 2005 and later ratified as Decree #2366 on 20/06/2009), is another important document typically referred to for guidance for urban planning and for existing and proposed land uses in Lebanon. Although, here again, there is no reference for measures to be taken to reduce the impacts on the urban climate.

The zoning plan of Ecochard (dated 1963) is another important document referred to for guidance by architects and planners with respect to specific limitations for building plots within each of the 10 respective zones of Beirut. However, some deficiencies are also found here, such as in the implementation of allowable building heights by developers; this is relatively lax as evidenced by the process of obtaining permits for buildings above maximum permissible heights which has been somewhat facilitated due in part to weaknesses in the existing administrative framework, including the low number of skilled staff and low salaries. In addition, the relevant authorities and/or parties are not adequately informed of the significance of protecting the urban climate.

Having conducted an extensive literature review and assessment of the existing Beirut context, simulations of the existing urban conditions for Beirut city were carried out as seen in the 4 th section of this thesis. To enable better awareness policies, be it as developers, planners, architects or simply citizens who have a relative influence on some of the factors affecting the climate, it is necessary to present the results related to the temperature of the city. Simulations using TEB modeling scheme were therefore carried out. The goal was initially to model the UHI from a description of Beirut (based on the aerial orthophotograph of Beirut dated 2008) with a grid mesh having a scale of 200 x 200m.Results of the simulations confirmed the predominant role played by the radiative parameters in the energy balance of the city in the summer. During the winter, on the other hand, it is the thermal insulation that has the greatest influence, as seen, for example in the results under the scenario which modifies the glass ratio of buildings. Although simulation results for modification of vegetation fractions were not as significant as expected, all results were consistent with current studies, which showed that increasing both the albedo of surface materials and vegetation fraction in cities have a great advantage in reducing the impacts of the urban heat island phenomenon, specifically on urban dwellers.

The form of the built environment influences the amount and fraction of wall surfaces, roads and roofs. Thus, changes in this form results in modifications to the energy balance due not only to a change in the exposure to solar radiation of different surfaces, but also due to a change in their fraction, considering that each surface possesses its own physical characteristics and therefore has a different thermal behaviour.

The influence of the shape or form of the built environment on the energy balance is therefore a complex one.

Finally, in the 5 th and last section of this thesis, recommendations are made for improvements in the communication network that currently exists between the various relevant authorities and parties, most notably the Municipality of Beirut, the Higher Council for Urban Planning (HCUP) and the Directorate General of Urban Planning (DGUP) since urban climatic knowledge amongst these parties is relatively limited.

Currently the Lebanese Green Building Council or LGBCan NGO that is quite actively involved in raising awareness on thermal standards for energy efficiency of buildingshas no influence on the decisions made by the relevant urban planning authorities. However, their participation and involvement as a stakeholder could be highly beneficial in transmitting the necessary knowledge on urban climatic issues due to the organization's involvement in providing a Lebanese certification system for buildings known as "Arz" that adopt environmental parameters and transform the way buildings and communities are designed into a prosperous environment that improves the quality of urban life. Academic institutions could also be actively involved in the transfer of urban climatic knowledge especially when considering the numerous works being conducted in these institutions that are paying increased attention to the topic of climate change, urban climate and adaptation measures. Of course multi-disciplinary coordination would be required at all times between all the relevant disciplines to ensure strategic and sustainable urban planning for Beirut and this could be achieved through the establishment of an urban climate agency or council.

Recommendations are also made in this 5 th section for the need to modify relevant urban policies in the Urban Planning Law #69 (dated 1983) and Building Code #646 (dated 2004) of Lebanon. For example, for the case of the UP Law, the environmental elements already considered in the existing 8 out of 43 articles should be further elaborated to emphasize the importance of also protecting the urban climate. By introducing this specific requirement in the urban planning law under which Lebanon functions today, the preliminary vital step that identifies the need to protect the urban climate would have been achieved. As for the Building Code, this should also be further elaborated upon to introduce new components that more specifically target the construction of new buildings, which make up 0.6% of the existing building stock in Beirut, as well as the rehabilitation of the existing building stock in Beirut, with the aim to mitigate the impacts of the urban heat island. As such, the modified building code should specify the following: 1) new buildings should adhere to the maximum allowable building height limitations as per the zoning specifications; 2) new as well as existing buildings should implement cool roof strategies, with albedo ranging between 0.6-0.8, which has the most significant impact on alleviating urban heat island as per the simulations results on TEB; 3) new buildings should have a glass ratio of less than 40% so as to avoid exacerbation of the urban heat island; and, 4) all buildings, new and existing, must ensure planting of at least one row of urban trees (preferably pinus pinea or ficus nitida which are considered to be native trees and which require minimal water intake) around the building perimeter in order to increase the fraction of urban vegetation in the city.

The need to implement more stringent measures for the permitting and approval process for new buildings is therefore vital to achieve successful results. Regarding the need to increase urban vegetation around existing buildings, these can potentially be enforced upon homeowner's payment of annual fees for water supply at the Beirut and Mount Lebanon Water Authority, which is part of the Ministry of Energy and Water (MOEW). As for enforcement of the proposed cool roofing strategy for existing buildings, this can potentially be achieved upon payment of electricity bills for example and further, by raising awareness for lower electricity bills by cool roofs, similar to the approach for the successful solar water heating campaign implemented a few years ago. This campaign, however, should be conducted through the joint efforts of MOEW and MOE. This research can therefore help bring together all relevant stakeholders, including researchers and policy makers and concerned authorities, to recognize the significance of the findings of this research, the various associated health risks and the future well-being or urban residents, the necessary steps that need to be taken to improve the transfer of urban climatic knowledge, the need to modify existing policies and to accordingly implement mitigative actions for cool roofing and urban greening of the city. These aforementioned recommendations were based on TEB simulation results conducted in this research, which stressed that "cool roof strategies" and "urban greening strategies" have the most significant impact on reducing the unpleasant impacts of the urban heat island in Beirut. This research also proposed that the relevant urban planning and decision-making authorities in Lebanon can make sustainable urban planning decisions for city scale by referring to TEB simulation results. This could successfully be achieved through implementation of the evidence-based planning approach which could be advantageous for the Beirut context where TEB acts as the scientific tool to provide the scientific evidence required for future sustainable decision-making in urban planning and design of the city.

Therefore, the aim of this research is to potentially provide the incentive and detailed guidance to concerned policy makers to modify the two legal documents of relevance, namely the Urban Planning Law #69 under which Lebanon currently functions today, and the Building Code #646, which is the centerpiece of all construction activities in Lebanon, with the aim to protect the urban climate in Lebanon. By making these modifications as detailed above, by establishing an agency or council that deals solely with urban climatic issues, by ensuring the systematic implementation of the proposed modifications to existing urban planning and building code through the joint efforts of all involved stakeholders, and by strengthening the existing institutional framework through employment of skilled and trained staff with frequent documentation and reporting and continuous follow-up, the first vital steps toward combatting the urban heat island of Beirut could essentially be achieved.

Regarding the limitations of this research, the potential impact of street orientations was not assessed since TEB does not provide this option. Consideration of this urban geometric parameter could be important in assessing the feasibility of this future mitigation scenario since it can affect exposure to solar radiation and accordingly impact heating and cooling energy demands. Architectural data entry for each x, y grid cell was also somewhat simplified in TEB, thus raising the possibility of inaccurate data representation. Having said this, TEB has been validated in numerous studies and is therefore considered to be a reliable and accurate modeling scheme for analysis of the UHI.

Moreover, this research considered patterns of existing urban form of Beirut as opposed to real values, as these data were either limited or unavailable; as such the required data were obtained by extrapolations from the most recent aerial image of Beirut dated 2008. Furthermore, it was not possible to access weather records from operating weather stations within the administrative boundary of Beirut due to either data inconsistencies or operational problems of weather stations or because they were not provided by the relevant authorities. The distance of over 3 km of the selected weather station from the study area can be considered to be another limitation of this research although simulation results were found to be acceptable and consistent with similar studies in Paris, Marseille, and Athens.

As for future research works, it would be interesting to investigate the actual possibility of intervention and implementation of strategic mitigating actions for Beirut given its architecture, its urban form, and so on. It would also be interesting to identify additional economic or social constraints which may hinder the effective implementation of a new policy pertaining to the protection of the urban climate. Conversely, these different strategies could result in extra economic gain as seen for the case of the recent implementation of solar water heating for an impressive number of home owners across Beirut. Moreover, it would be interesting to investigate the effects of the existing transportation and infrastructure sectors as well as anthropogenic heat emissions on the UHI of Beirut as this research focused primarily on the existing urban geometric characteristics of the city. Indeed the implementation of the proposed mitigating scenarios in this research coupled with the need to reduce traffic emissions by improving non-motorised mobility could also be considered in future urban planning scenarios that could potentially reduce UHI impacts in Beirut. Furthermore, the impacts of the existing urban morphology and anthropogenic heat emissions on urban heat stress could also be investigated.

In addition to the need to examine and revise areas of the existing Urban Planning Law #69 and Building Code #646, the question of the possibility to integrate protection of the urban climate has to be consciously considered and investigated in the practice of urban planning and design parameters. The need to understand why such modifications are important to certain parties but of less interest to other parties needs likewise to be examined.

The economy may similarly help as it has for the reduction of greenhouse gas emissions in other cities worldwide, for example, which reflects the need to create tools to facilitate the implementation of proposed strategies to reduce impacts on the urban climate. As such, implementation of cool roof strategies and urban greening strategies can be advocated by relevant authorities like the Higher Council for Urban Planning (HCUP), the Order of Engineers and Architects, MOEW and the Ministry of Environment (MOE). These strategies can be economically beneficial since they can generate additional business opportunities and accordingly boost the economy for markets specialized in cool roofing and urban soft landscaping.

The need to examine various other urban planning and design approaches could additionally be interesting for the Beirut context, such as the investigation of the impacts of cooling by increasing evaporation, cooling by implementation of water-film surfaces, implementation of infrastructure that utilize water, implementation of green infrastructure, active and passive cooling, thermal efficiency of buildings, and urban heat stress. These aforementioned actions could also be considered in future urban planning investigations for Beirut within the context of future urban heat island mitigation scenarios. Having said this, undoubtedly the question of the feasibility of implementation of the aforementioned water scenarios arises. Although Lebanon has a favourable share of water resources relative to other countries in the region [START_REF] El-Fadel | Temporal variation of leachate quality from pre-sorted and baled municipal solid waste with high organic and moisture content[END_REF], temporally inconsistent rainfall patterns combined with seasonal water shortages and saline intrusion increase the danger of water resource scarcity in Beirut. Water resources in Lebanon are particularly vulnerable to higher temperatures and changes in patterns of precipitation [START_REF] Hatzaki | Information sheet on observed climate indicators for the CIRCE urban case studies[END_REF]. Water shortages can constrain economic growth and present a complex challenge for future development, which is why it is imperative to properly manage the collection and distribution of water resources in the country. Indeed, one such example to achieve this goal can be found in the current works being carried out between the Council for Development and Reconstruction (CDR) and MOEW with design and funding plans being carried out in affiliation with the World Bank almost finalized to build the Bisri Dam (www.cdr.gov.lb) situated toward the south of Lebanon with the aim to boost water supply to the residents of Beirut. This would potentially significantly improve the water shortage problem in Beirut not to mention the potential to more successfully implement the aforementioned urban cooling scenarios. Up until such time however, it is recommended to allocate select pilot study areas for application and testing of the success of this proposed water cooling scenario. Other research areas of interest that could be examined include for example a comparison of approaches and decision-making tools used to combat the UHI with other cities that are similar to Beirut or are in the region like Athens, Amman, Barcelona or Paris; this could be especially useful in identifying strengths and weaknesses in the existing system in Beirut and a means for improvement of the approaches used to mitigate UHI (Kaloustian, Diab, Bechtel, & Oseenbrügge).

Finally, it would be interesting to obtain and conduct simulations based on real values of data as opposed to extrapolated data and this could potentially be achieved by collaborative works between the relevant authorities like MOEW and the MOE, urban planning authorities and policy makers, and reputable academic institutions like the American University of Beirut or Université Saint Joseph. Indeed these latter academic institutions have recently been showing more interest in this topic and could possibly more easily arrange for funding required to conduct such a large scale campaign. The evidence-based planning approach which has been recommended in this research could help facilitate this collaboration between the relevant parties. In addition, weather records from their operational stations could be accessed and simulations could essentially be compared and used for validation of results in this research. Therefore in this latter case, the need to improve the transfer of urban climatic knowledge can be achieved through collaborative efforts between policy makers and academic research institutions.

To conclude, this thesis contributed to a better understanding of the urban environment of the city of Beirut and the respective urban parameters that have the most significant impact on reducing some of the effects of the urban heat island phenomenon.

In doing so, this research has paved the way for further work on reducing the UHI effect

  not have been possible: the Neighborhood Initiative of the American University of Beirut led by Dr. Cynthia Myntti; the Lebanese Agricultural Research Institute (LARI) headed by Dr. Michel Afram; the Central Administration of Statistics (CAS); the Ministry of Energy of Water; the Ministry of Environment; Directorate General of Urban Planning;

Figure 1 .

 1 Figure 1. Schematic representation of the urban heat island profile in Paris. Source: Descartes Team Grand Paris, 2009 ................................................................................................................

Figure 2 .

 2 Figure 2. Flow chart showing thesis structure ...............................................................................

Figure 3 .

 3 Figure 3. Schematic depiction of the main components of the urban atmosphere. Source: Voogt, 2004 ...............................................................................................................................................

Figure 4 .

 4 Figure 4. Site characteristics of highest mean daytime UHI location in each estate. Source: Giridharan et al, 2007, pp. 3673 ....................................................................................................

Figure 5 .

 5 Figure 5. UHI associated deaths in Paris. Source: INVS, 2015 ....................................................

Figure 6 .

 6 Figure 6. Heat storm and heat island during the summer of 2003. Source: Akbari, 2014 ............

Figure 7 .

 7 Figure7. The influence of building air flow on pollution dispersion. Source:Oke, 1987, pp.273

Figure 9 :

 9 Figure 9: Structure of NARP-LUMPS. Source: Grimmond and Oke, 2002, pp. 793 ...................

Figure 10 .

 10 Figure 10. (a) Scheme of the SM2-U energy and water budget models with 8 surface types (pav, cova, bare, nat, roof, vega, ven, wat) and 3 layers of soil. (b) Energy budget of paved surfaces. Source: Mestayer, et al., 2004, pp.3 ............................................................................................

  Figure 10. (a) Scheme of the SM2-U energy and water budget models with 8 surface types (pav, cova, bare, nat, roof, vega, ven, wat) and 3 layers of soil. (b) Energy budget of paved surfaces. Source: Mestayer, et al., 2004, pp.3 ............................................................................................

Figure 11 .

 11 Figure 11. Design of the ENVI-met database system in Version 4.0. Source: www.envi-met.info/ .....................................................................................................................................................

Figure 12 .

 12 Figure12. Output of ENVI-met for a study conducted in a linear park area in Phoenix,Arizona. Source:Ozkeresteci, Crewe, Brazel, and Bruse, 2003, pp. 405 ..................................................

Figure 13 .

 13 Figure 13.Surface temperatures and solar flux calculated at building surfaces, trees and on the ground. Source: Antoine et al., 1998; UMR 1563 Architectural and urban atmospheres, 2002-2005. ............................................................................................................................................

Figure 14 .

 14 Figure 14. Representation of surface fluxes. Source: Colombert, 2008 ......................................

Figure 15 .

 15 Figure 15. Schematic representation of surfaces (roof, wall, road indicated by subscript R, w, and r, respectively), prognostic temperatures (T) and aerodynamic resistances (R) used in TEB and the output fluxes. Resistances are shown with thick lines. Source: Masson et al., 2002, pp.1015 .....................................................................................................................................................

Figure 16

 16 Figure 16. a. Comparison of tiling approaches applied in TEB_ISBA (top) and TEB_Veg (bottom) to compute surface fluxes for a SURFEX's grid point containing pervious and impervious covers. Source: Lemonsu et al., 2012, pp.1378 ........................................................

Figure 17 .

 17 Figure 17. Diagram describing the inclusion of urban vegetation in the TEB's code within the tiling approach of SURFEX. Source: Lemonsu et al, 2012, pp. 1380 .........................................

Figure 18 .

 18 Figure 18. Diagram of a building and an urban canyon. The main physical processes included in BEM-TEB are represented: heat storage in building and urban construction materials, internal heat gains, solar heat fluxes, waste heat from HVAC systems, etc. Source: Bueno et al, 2012, pp. 435 ...............................................................................................................................................

Figure 19 .

 19 Figure 19. Illustration of the numerical grid in the urban module and the geometrical urban parameters: street canyon width (WS), building width (WB), iu are the face and IU the center of the urban model levels and building height distribution in terms of γ and Γ. Source. Martilli, et al. 2002, pp. 267 ...............................................................................................................................

Figure 20 .

 20 Figure 20. Schematic view of multi-layer urban surface schemes: the interactions between the surface scheme and the atmosphere are drawn in thick-dashed lines. Source: Masson, 2006, pp. 40 .................................................................................................................................................

Figure 21 .

 21 Figure 21. Methodology for energy and air quality. Source: Akbari, 2005, pp. 13 ....................

Figure 22 .

 22 Figure 22. Temperatures of surfaces with and without vegetation. Source: Wong, et al., 2003, pp. 358 ...............................................................................................................................................

Figure 23 .

 23 Figure 23. Comparison of environmental conditions at 1.5m above the ground on a typicaly summer day with two ground surface materials. Source: Akbari, 2014 ......................................

Figure 24

 24 Figure 24 Map showing physical characteristics of the city of Beirut..Source: Directorate of Geographic Affairs, 25-30cm pixel, 2008 ...................................................................................

Figure 25 .

 25 Figure 25. Number of 'hot days' (Tx > 31°C) anomalies from the 1971-2000 average (left axis, bars) for the Beirut International Airport (BIA) station. 10-year moving average of 'hot days' (right axis, solid line) for the BIA station. Source: Hatzaki, et al. 2010; CIRCE urban case studies: Beirut ...........................................................................................................................................

Figure 26 .

 26 Figure 26. The administrative areas of Beirut. Source. Department of Geographic Affairs, 25-30cm pixel (aerial photograph) ...................................................................................................

Figure 27 .

 27 Figure 27. Growth of Beirut and Lebanon Population from 1896 to 2005 adapted from Yassin, 2012 .............................................................................................................................................

Figure 28 .

 28 Figure 28. Population versus Tmax and Tmin. Source: Saliba 1998 (population) and AUB 2013 (climatic data) (prepared by author) ............................................................................................

Figure 29 .

 29 Figure 29. Beirut phases of urbanization. Source: Yassin, 2012, pp. 67 .....................................

Figure 30 .

 30 Figure 30. Location of Palestinian refugee camps in Beirut. Source: Google Earth, 2015 .........

Figure 31 .

 31 Figure 31.Image of haphazardly construction buildings in a Palestinian refugee camp in Beirut. Source: UNRWA, 2015 ...............................................................................................................

Figure 32 .

 32 Figure 32. BCD Master Plan: A-Treelined sea-side promenade, B-Seaside park, 1-Public & Religious Buildings, 2-Preserved historic core of the city, 3-Financial district mixed use of offices, recreational & shopping facilities, 4-Traditional old souks area, 5-Mixed use area, 6-Residential area, 7-Public parks & squares, 8-Archeological excavation area, 9-Marinas. Source: http://www.lebanon.com/construction/beirut/masterp.htm .........................................................

Figure 33 .

 33 Figure 33. Zoning for Beirut administrative area. Source: Ecochard, 1963 ................................

Figure 34 .

 34 Figure 34. Map of Beirut city showing built environment including road networks (prepared by author) .........................................................................................................................................

Figure 35 .

 35 Figure 35. Land use-land cover map. Source: CDR. NPMPLT /DAR-IAURIF, 2004 ...............

Figure 36 .

 36 Figure 36. Dense urban fabric in Mazraa ....................................................................................

Figure 37 .

 37 Figure 37. Medium density urban fabric in Ras Beirut ...............................................................

Figure 38 .

 38 Figure 38. Dense informal urban fabric in Moussaytbeh ............................................................

Figure 39 .

 39 Figure 39. Building constructed circa 1940s in Ras Beirut area with light-coloured facades with approximate (α) of 0.7 (photograph taken by author) .................................................................

Figure 40 .

 40 Figure 40. Building constructed circa 1950s in Zokak El Blat with light-coloured facades with approximate (α) of 0.7 (photograph taken by author) .................................................................

Figure 41 .

 41 Figure 41. Newly constructed building with concrete rooftop in Beirut with approximate α of 0.225 (photograph taken by author) ............................................................................................

Figure 42 .

 42 Figure 42. Vulnerability to UHI impacts in Beirut ......................................................................

Figure 43 .

 43 Figure 43. Schematic representation of the MOSES2 surface tile scheme representing land surfaces within a single model grid cell. Source: McCarthy, 2009; Report on CIRCE, urban heat island simulations ........................................................................................................................

Figure 44 .

 44 Figure 44. Surface energy balance of the urban canopy model. Source. Best, et al. 2006, pp. 506 .....................................................................................................................................................

Figure 45 .

 45 Figure 45. Annual difference in UHI magnitude between three Mediterranean cities adapted from McCarthy, 2009; Report on CIRCE, urban heat island simulations............................................

Figure 46 .

 46 Figure 46. Surface temperatures dated 21 May 2000 at 8h12min courtesy of LANDSAT 7 ETM+ .....................................................................................................................................................

Figure 47 .

 47 Figure 47. Location of five weather stations within and outside of Beirut. Source: Google Earth, 2013 .............................................................................................................................................

Figure 48 .

 48 Figure 48. Flow chart showing elimination process for modeling schemes and selection of TEB for UHI simulations in Beirut (prepared by author) ....................................................................

Figure 49 .

 49 Figure 49. Flow chart showing various steps taken in data collection process for Beirut...........

Figure 50 .

 50 Figure 50. Identification of building age groups in Beirut by extrapolation on ArcGIS of aerial images for the years 1971, 1998, 2008. Source (aerial images): Direction des Affairs Geographiques. ............................................................................................................................

Figure 51 .

 51 Figure 51. Classification of roof types in Beirut based on extrapolations on ArcGIS. ...............

Figure 52 .

 52 Figure 52. Road classification into primary, secondary and tertiary roads by extrapolation using aerial image dated 2008. Source: Direction des Affairs Geographiques .....................................

Figure 53 .

 53 Figure 53. Ficus Nitida vegetation type typically found in Beirut garden/green areas and street trees with LAI of 2 (photographs taken by author) .....................................................................

Figure 54 .

 54 Figure 54. Pinus Pinea vegetation type typically found in Beirut garden/green areas with LAI of 2 (photographs taken by author) .....................................................................................................

Figure 55 .

 55 Figure 55. Selected cells for the purpose of distinct comparison of simulation results ...............

Figure 56 .

 56 Figure 56. Canyon temperature simulations for the Control Run across Beirut on 01-July at 1200 UTC .............................................................................................................................................

Figure 57 .

 57 Figure 57. Canyon temperature simulations for the Control Run across Beirut on 01-February at 1200 UTC ....................................................................................................................................

Figure 58 .

 58 Figure 58. Evolution of canyon temperatures for five selected cells on 01-February .................

Figure 59 .

 59 Figure 59. Evolution of canyon temperatures for five selected cells on 01-July .........................

Figure 60 .

 60 Figure 60. Evolution of surface roof temperatures for two selected cells on 01-February .........

Figure 61 .

 61 Figure 61. Evolution of surface roof temperatures for two selected cells on 01-July .................

Figure 62 .

 62 Figure 62. Roof temperature simulations for the Control Run across Beirut on 01-February at 1200 UTC ....................................................................................................................................

Figure 63 .

 63 Figure 63. Roof temperature simulations for the Control Run across Beirut on 01-July at 1200 UTC .............................................................................................................................................

Figure 64 .

 64 Figure 64.Surface road temperature simulation results for Control Run across Beirut on 01-February at 1200 UTC .................................................................................................................

Figure 65 .

 65 Figure 65. Surface road temperature simulation results for Control Run across Beirut on 01-July at 1200 UTC ................................................................................................................................

Figure 66 .

 66 Figure 66. Evolution of surface road temperatures for two selected cells on 01-July .................

Figure 67 .

 67 Figure 67. Evolution of surface road temperatures for two selected cells on 01-February .........

Figure 68 .

 68 Figure 68. Internal building temperature for the Control Run across Beirut at midday on 01-February at 1200 UTC .................................................................................................................

Figure 69 .

 69 Figure 69. Wall temperature for the Control Run across Beirut at midday on 01-July at 1200 UTC .....................................................................................................................................................

Figure 70 .

 70 Figure 70. Temperature evolution of wall temperatures for three selected cells on 01-February Figure 71. Temperature evolution of wall temperatures for three selected cells on 01-July .......

Figure 72 .

 72 Figure 72. Temporal evolution of internal building temperature for five selected cells at midday on 01-February ............................................................................................................................

Figure 73 .

 73 Figure 73. Temporal evolution of internal building temperatures for five selected cells at midday on 01-July ....................................................................................................................................

Figure 74 .

 74 Figure 74. Cooling energy demand for Control Run across Beirut on 01-July at 1200 UTC .....

Figure 75 .

 75 Figure 75. Evolution of cooling energy demand for two selected cells on 01-July ....................

Figure 76 .

 76 Figure 76. Evolution of heating energy demand for three selected cells on 01-February ...........

Figure 77 .

 77 Figure 77. Heating energy demand for Control Run across Beirut on 01-February at 2000 UTC .....................................................................................................................................................

Figure 78 .

 78 Figure 78. Comparison of canyon temperatures between Scenario 1 and Control Run on 01-February.......................................................................................................................................

Figure 79 .

 79 Figure 79. Comparison of canyon temperatures ..........................................................................

Figure 81 .

 81 Figure 81. Comparison of roof temperature between Scenario 1 and Control Run on 01-July .

Figure 80 .

 80 Figure 80. Comparison of roof temperature between Scenario 1 and Control Run on 01-February .....................................................................................................................................................

Figure 82 .

 82 Figure 82. Comparison of road temperature between Scenario 1 and Control Run on 01-February .....................................................................................................................................................

Figure 83 .

 83 Figure 83.Comparison of road temperature between Scenario 1 and Control Run on 01-July ...

Figure 84 .

 84 Figure 84. Comparison of wall temperature between Scenario 1 and Control Run on 01-February .....................................................................................................................................................

Figure 85 .

 85 Figure 85. Comparison of wall temperature between Scenario 1 and Control Run on 01-July .

Figure 86 .

 86 Figure 86. Comparison of internal building temperatures between Scenario 1 and Control Run on 01-February .................................................................................................................................

Figure 87 .

 87 Figure 87. Comparison of internal building temperature between Scenario 1 and Control Run on 01-July .........................................................................................................................................

Figure 89 .

 89 Figure 89. Comparison of HVAC_HT between Scenario 1 and Control Run on 01-February ...

Figure 88 .

 88 Figure 88. Comparison of HVAC_CL between Scenario 1 and Control Run on 01-July ...........

Figure 90 .

 90 Figure 90. Comparison of canyon temperatures between Scenario 2 and Control Run on 01-February.......................................................................................................................................

Figure 91 .

 91 Figure 91. Comparison of canyon temperatures between Scenario 2 and Control Run on 01-July .....................................................................................................................................................

Figure 92 .

 92 Figure 92. Comparison of road temperatures between Scenario 2 and Control Run on 01-February .....................................................................................................................................................

Figure 93 .

 93 Figure 93. Comparison of road temperatures between Scenario 2 and Control Run on 01-July

Figure 95 .

 95 Figure 95. Comparison of roof temperatures between Scenario 2 and Control Run on 01-July .

Figure 96 .

 96 Figure 96. Comparison of wall temperatures between Scenario 2 and Control Run on 01-February .....................................................................................................................................................

Figure 97 .

 97 Figure 97. Comparison of wall temperatures between Scenario 2 and Control Run on 01-July .

Figure 98 .

 98 Figure 98. Comparison of internal building temperatures between Scenario 2 and Control Run on 01-February .................................................................................................................................

Figure 99 .

 99 Figure 99. Comparison of internal building temperatures between Scenario 2 and Control Run on 01-July .........................................................................................................................................

Figure 100 .

 100 Figure 100. Comparison of cooling energy demand between Scenario 2 and Control Run on 01-February.......................................................................................................................................

Figure 101 .

 101 Figure 101. Comparison of heating energy demand between Scenario 2 and Control Run on 01-July ..............................................................................................................................................

Figure 102 .

 102 Figure 102. Comparison of cooling energy demand between Scenario 3 and Control Run on 01-February.......................................................................................................................................

Figure 103 .

 103 Figure 103. Comparison of heating energy demand between Scenario 3 and Control Run on 01-July ..............................................................................................................................................

Figure 104 .

 104 Figure 104. Comparison of heating energy demand between Scenario 4 and Control Run on 01-February.......................................................................................................................................

Figure 105 .

 105 Figure 105. Comparison of cooling energy demand between Scenario 4 and Control Run on 01-July ..............................................................................................................................................

Figure 106 .

 106 Figure 106. Comparison of cooling energy demand between Scenario 5 and Control Run on 01-February.......................................................................................................................................

Figure 107 .

 107 Figure 107. Comparison of heating energy demand between Scenario 5 and Control Run on 01-July ..............................................................................................................................................

Figure 108 .

 108 Figure 108. Comparison of cooling energy demand ...................................................................

Figure 109 .

 109 Figure 109. Comparison of heating energy demand between Scenario 6 and Control Run on 01-July ..............................................................................................................................................

Figure 110 .

 110 Figure 110. Solar radiation received in a canyon perpendicular to the sun direction; left hand: sun low over the horizon (λ > λ0); right hand: sun high over the horizon (λ < λ0). Source: Masson, 2000, pp.368 ................................................................................................................................

Figure 111 .

 111 Figure 111. Flow chart of first objective of this research ............................................................

Figure 112 .

 112 Figure 112. Mexican researchers modeled significant cooling energy savings from cool roofs. Source: Akbari, 2014 ...................................................................................................................

Figure 113 .

 113 Figure 113. Materials performance testing for roofs from 26 to 29 August. Source: Akbari, 2014 .....................................................................................................................................................

Figure 114 .

 114 Figure 114. Recommended organization chart for the transfer of urban climatic knowledge amongst all parties involved in urban planning process in Beirut ...............................................

Figure 115 .

 115 Figure 115. Recommended evidence-based planning approach to mitigate UHI impact in Beirut .....................................................................................................................................................

Figure 116 .

 116 Figure 116. View of Sama Beirut Tower in Ashrafiyeh as well as five more high rises under construction as seen in the background (photograph taken by author) .......................................

  .................................................................................................................................... Table 2: Albedo values for various urban surfaces according to NASA, 2012 and Oke, 1987 .... Table 3. Description of three different urban patterns examined for optimal thermal conditions Source: Fahmy and Sharples, 2008 ...............................................................................................Table 4. UHI empirical generalizations adapted from Arnfield, 2003 .......................................... Table 5. Limitations and advantages of various existing measurement types for UHI (prepared by author) ........................................................................................................................................... Table 6. Summary of various different urban surface exchange modeling schemes (prepared by author) ......................................................................................................................................... Table 7. Description of various UHI mitigation strategies implemented and/or studied worldwide with successful results (prepared by author) ............................................................................... Table 8. Outline of history of urban planning of Beirutand respective environmental considerations (prepared by author) ............................................................................................ Table 9. Palestinian refugee camps in Beirut adapted from Fawaz and Peillen, 2002 ................ Table 10. Environmental implications of Building Code #646adapted from MOE/UNDP/ECODIT, 2011 ...................................................................................................... Table 11. Key authorities and other non-governmental authorities involved in the urban planning process in Beirut .......................................................................................................................... Table 12. Land Use Classifications according to NPMPLT ........................................................ Table 13. Levels of land cover-land use classifications .............................................................. Table 14. Albedo (α) of dominating artificial urban surfaces in Beirut adapted from Oke (1987) (prepared by author) ....................................................................................................................Table 15. Criteria for comparison of various available measurement tools ................................ Table 16. Data on climatic stations within and outside Beirut administrative area..................... Table 17. Nature of data required to run TEB ............................................................................. Table 18. Forcing / climatic data / files required for TEB/SURFEX and necessity for Beirut case ..................................................................................................................................................... Table 19. Physical data collected for TEB analysis for Beirut from relevant authorities and institutions in Lebanon ................................................................................................................ Table 20. Data on building wall layers in Beirut depending on building age group adapted from Oke (1987) (prepared by author) ................................................................................................. Table 21. Building count in each age group (prepared by author) .............................................. Table 22. Data on internal floor materials of buildings in Beirut based on age group category (prepared by author) .................................................................................................................... Table 23. Data regarding rooftops in Beirut adapted from Oke (1987) (prepared by author) ..... Table 24. Sample grid cells in Moussaytbeh and Mazraa areas showing summation of town cover fractions ....................................................................................................................................... Table 25. Selected cells with contrasting cover fractions ............................................................ Table 26. Devised scenarios run on TEB .................................................................................... Table 27. Output results for all six scenarios in comparison to control run results ..................... Table 28. Summary of results for the devised scenarios and their suitability for the Beirut context ..................................................................................................................................................... Table 29. Summary of assessment of environmental and urban microclimatic considerations in urban planning context of Beirut ................................................................................................. Table 30. Environmental dimensions considered within the Urban Planning Law #69 (dated 1983) and corresponding weaknesses and opportunities in terms of climatic issues .................. Table 31. Recommendations for modifications of the Building Code #646 (dated 2004) of Lebanon .......................................................................................................................................

Figure 1 .

 1 Figure 1. Schematic representation of the urban heat island profile in Paris. Source: Descartes Team Grand Paris, 2009

  Figure 2. Flow chart showing thesis structure

  It is therefore important to study the effects of urbanization on the urban heat island in Beirut to determine to what extent energy demands are affected and what the potential consequences are on the surrounding environment and urban microclimate.

Figure 3 .

 3 Figure3. Schematic depiction of the main components of the urban atmosphere. Source:[START_REF] Voogt | Urban heat islands: hotter cities[END_REF]

Figure 4 .

 4 Figure 4. Site characteristics of highest mean daytime UHI location in each estate. Source: Giridharan et al,2007, pp. 3673

Figure 5 .Figure 6 .

 56 Figure 5. UHI associated deaths in Paris. Source: INVS, 2015

Figure 7 .

 7 Figure7. The influence of building air flow on pollution dispersion. Source:Oke, 1987, pp.273

  the net energy storage; rate per unit volume (per unit horizontal area) -ΔQ A is the net energy (sensible and latent) advection; rate per unit volume (per unit horizontal area)

  controlled by human decisions responding to the activity rhythms only indirectly related to the solar cycle. Finally, ΔQ A refers to the net horizontal transfer of sensible and latent heat through the sides of the building-air volume. Figure8is a schematic representation of the fluxes involved in the energy balance of an urban building air volume. This has been referred to in numerous related researches and is indeed the basic figure in climatology.

Figure 8 .

 8 Figure 8. Schematic depiction of the fluxes involved in the energy balance of an urban building air volume.Source:Oke, 1987, pp.275

  various surface types and vegetation to indicate areas most sensitive to the impacts of the UHI as opposed to actually measuring the UHI intensity in a city. This is still advantageous however since the information can accordingly help to devise solutions at the city scale as to the areas which would benefit the most through implementation of mitigating solutions, such as the plantation of more urban trees along asphalted roads of low solar reflectivity or in areas which are characterized by a high fraction of artificial surfaces. Therefore they can be very helpful in this respect. Aerial orthophotos do exist for Beirut although they are difficult to obtain as only the military has access to them and in addition they are quite costly. Having said this, the most recent aerial orthophoto that exists for Beirut, which is dated 2008, was obtained and accordingly used to identify main areas of vegetation, densely built areas and roads. Although it is 7 years old, comparison with the recent satellite image (from Google Earth) showed only very minor changes since 2008. It is worth also noting that for the purpose of this research, ArcGIS software was used to inspect more closely and in more detail the aerial orthophoto for Beirut administrative area and to extrapolate necessary information regarding urban surfaces from it (see Part IV of this research for more details).

  the net energy storage; rate per unit volume (per unit horizontal area) NARP-LUMPS is based on several stages as indicated in flow chart of the structure of LUMPS in Figure9, which shows that it is driven by relatively easily obtained meteorological and surface data. Heat storage by the urban fabric is parameterized from net all-wave radiation and surface cover information.Flow chart of the struction of LUMPS. Quantities in parenthesis are needed only if net all-wave radiation Q* or incoming shortwave radiation K ↓ are not measured. T a is the air temperature, e a is actual vapor pressure, c f is the cloud fraction, P is pressure, U is wind speed, ΔQ S is storage heat flux, Q H is the turbulent sensible heat flux density, Q E is the latent heat flux density, L is Monin Obukhov length 15 and u* is the friction velocity 16 Figure9: Structure of NARP-LUMPS. Source:Grimmond and Oke, 2002, pp. 793

Figure 10 .

 10 Figure 10. (a) Scheme of the SM2-U energy and water budget models with 8 surface types (pav, cova, bare, nat, roof, vega, ven, wat) and 3 layers of soil. (b) Energy budget of paved surfaces. Source:Mestayer, et al., 2004, pp.3

  a prognostic model based on the fundamental laws of fluid dynamics and thermodynamics. The model has many uses and indeed includes the simulation of the following processes: flow around and between buildings; exchange processes at the ground surface and at building walls, building physics, impacts of vegetation of the local microclimate and pollutant dispersion. Since its first official release more than 10 years ago, ENVI-met model is constantly being developed further, and has accordingly undergone numerous upgrades as seen in its most recent Version 4.0[START_REF] Huttner | Numerical modeling of the urban climatea preview on ENVI-met 4.0[END_REF]. In prior versions of ENVI-met, the atmospheric boundary conditions of the simulation could only be adjusted by setting some initialization values from which ENVImet deduces directly (incoming radiation) or indirectly (wind speed, air temperature, humidity) the diurnal variation of the boundary conditions of the simulation. Although this approach facilitates the use of ENVI-met for non-scientists, unfortunately it allows only very limited influence on the development of the boundary conditions on which the results of a micro-scale model strongly depend. The most recent version of ENVI-met (Version 4.0) has taken into consideration these limitations and has made it possible to define the diurnal variation of the atmospheric boundary conditions and the incoming radiation. This allows a more accurate comparison between measurements and simulations of ENVI-met and allows the development of much more detailed weather scenarios for testing purposes

Figure 11 .

 11 Figure 11. Design of the ENVI-met database system in Version 4.0. Source: www.envi-met.info/

Figure 13 .

 13 Figure13.Surface temperatures and solar flux calculated at building surfaces, trees and on the ground. Source:[START_REF] Antoine | Assessing solar energy and environmental variables in urban outdoor spaces: a simulation tool[END_REF] UMR 1563 Architectural and urban atmospheres, 2002-2005.

  a meteorological or climate model or in a stand-alone (offline) mode. SURFEX is divided into 4 main tiles including NATURE, WATER, SEA and TOWN, which are all treated by different models whereby the town tile is represented by the Town Energy Balance (TEB) model while the vegetation tile is represented by the Integration with Soil Biosphere and Atmosphere (ISBA) model (see Figure14).

Figure 14 .

 14 Figure 14. Representation of surface fluxes. Source: Colombert, 2008

Figure 15 .

 15 Figure 15. Schematic representation of surfaces (roof, wall, road indicated by subscript R, w, and r, respectively), prognostic temperatures (T) and aerodynamic resistances (R) used in TEB and the output fluxes. Resistances are shown with thick lines. Source:[START_REF] Masson | Evaluation of the Town Energy Balance (TEB) scheme with direct measurements from dry districts in two cities[END_REF]Masson et al., , pp.1015

  presents the comparison of tiling approaches in TEB-ISBA (top) and TEB_Veg (bottom) to compute surface fluxes and as can be seen the TEB_Veg approach considers the buildings, roads and gardens fractions all within the TEB tile. With respect to the functional processes, TEB_Veg model does not require implementation of new mechanisms but needs only adjustment of descriptive parameters such as the leaf area index (LAI) or tree height.

Figure 16 .

 16 Figure 16. a. Comparison of tiling approaches applied in TEB_ISBA (top) and TEB_Veg (bottom) to compute surface fluxes for a SURFEX's grid point containing pervious and impervious covers. Source:[START_REF] Lemonsu | Inclusion of vegetation in the Town Energy Balance model for modeling urban green areas[END_REF]Lemonsu et al., , pp.1378 Therefore, SURFEX tile dedicated to urban covers is now associated to the

Figure 17 .

 17 Figure17. Diagram describing the inclusion of urban vegetation in the TEB's code within the tiling approach of SURFEX. Source:[START_REF] Lemonsu | Inclusion of vegetation in the Town Energy Balance model for modeling urban green areas[END_REF]Lemonsu et al, , pp. 1380

Figure 18 .

 18 Figure18. Diagram of a building and an urban canyon. The main physical processes included in BEM-TEB are represented: heat storage in building and urban construction materials, internal heat gains, solar heat fluxes, waste heat from HVAC systems, etc. Source:Bueno et al, 2012, pp. 435

Figure 19 .

 19 Figure19. Illustration of the numerical grid in the urban module and the geometrical urban parameters: street canyon width (WS), building width (WB), iu are the face and IU the center of the urban model levels and building height distribution in terms of γ and Γ. Source.Martilli, et al. 2002, pp. 267

Figure 20 .

 20 Figure 20. Schematic view of multi-layer urban surface schemes: the interactions between the surface scheme and the atmosphere are drawn in thick-dashed lines. Source: Masson, 2006, pp. 40 4.2.3 Other modeling schemes: mesoscale and macroscale. This section of the

  Figure 21 presents these three aforementioned UHI mitigation strategies showing the associated processes that are accordingly affected as well as the results on the overall urban environment and quality of life.

Figure 21 .

 21 Figure 21. Methodology for energy and air quality. Source: Akbari, 2005, pp. 13

Figure 23 .

 23 Figure 23. Comparison of environmental conditions at 1.5m above the ground on a typicaly summer day with two ground surface materials. Source: Akbari, 2014

  figures illustrating the prevailing climatic conditions for Beirut city). These climatic

Figure 25 .

 25 Figure 25. Number of 'hot days' (Tx > 31°C) anomalies from the 1971-2000 average (left axis, bars) for the Beirut International Airport (BIA) station. 10-year moving average of 'hot days' (right axis, solid line) for the BIA station. Source: Hatzaki, et al. 2010; CIRCE urban case studies: Beirut

Figure 26 .

 26 Figure 26. The administrative areas of Beirut. Source. Department of Geographic Affairs, 25-30cm pixel (aerial photograph)

Figure 27 .Figure 28 .

 2728 Figure 27. Growth of Beirut and Lebanon Population from 1896 to 2005 adapted from Yassin, 2012

Figure 29 .

 29 Figure 29. Beirut phases of urbanization. Source: Yassin, 2012, pp. 67

Figure 30 .

 30 Figure 30. Location of Palestinian refugee camps in Beirut. Source: Google Earth, 2015

  settlements. Like other cities in the Third World, Beirut's recent urbanization has largely occurred around the tight framework of urban regulations giving rise to the so-called informal settlements, neighborhoods which have developed since the 1960s through the efforts of their current or prospective dwellers, in violation of urban and building regulations/ and or property rights[START_REF] Fawaz | Informal urban development/the Lebanese experience/brief overview[END_REF]. The informal settlements in Lebanon have been established due to a combination of factors but mainly due to local and regional history of violent conflicts such as the Lebanese civil war and the Arab-Israeli war, as well as the absence of affordable housing options especially for lowincome families (for a more extensive account of the associated contributing factors that have resulted in these informal settlements see[START_REF] Fawaz | Informal urban development/the Lebanese experience/brief overview[END_REF]. Most of these informal settlements lie in the suburbs of Beirut. Houses in these informal settlements are typically haphazardly constructed, are no more than two to maximum three storeys, have asphalted rooftops and with almost no space in between the buildings. Road conditions and infrastructure are also extremely poor; the roads are poorly paved, and are narrow where two cars in opposite directions can just barely pass by. These closely packed asphalted buildings can have significant impacts on the UHI of the city of Beirut due to their low solar reflective properties and poor or indeed non-existing urban planning. Again as previously mentioned, while this thesis does not attempt to analyze the specific impact of these types of informal buildings on the UHI of Beirut, it could be recommended as a topic for future research work. Having said this, they are integrated into the overall UHI analysis of the city of Beirut, without concentrating specifically on these informal settlement areas.

Figure 32 .

 32 Figure 32. BCD Master Plan: A-Treelined sea-side promenade, B-Seaside park, 1-Public & Religious Buildings, 2-Preserved historic core of the city, 3-Financial district mixed use of offices, recreational & shopping facilities, 4-Traditional old souks area, 5-Mixed use area, 6-Residential area, 7-Public parks & squares, 8-Archeological excavation area, 9-Marinas. Source: http://www.lebanon.com/construction/beirut/masterp.htm

Figure 33 .

 33 Figure 33. Zoning for Beirut administrative area. Source: Ecochard, 1963

  which fall primarily under the responsibility of the Ministry of Public Works and Transport (MOPWT): 1) Higher Council of Urban Planning (HCUP); 2) Directorate General of Urban Planning (DGUP); 3) Order of Engineers and Architects (OEA), 4) Regional Departments of Urban Planning; 5) Ministry of Interior and Municipalities (MOIM); 6) public bodies like the Lebanese Standards Institution (LIBNOR) attached to the Ministry of Industry (MOI), and; 7) the Municipality of Beirut.

Figure 35 .

 35 Figure 35. Land use-land cover map. Source: CDR. NPMPLT /DAR-IAURIF, 2004

Figure 36 .

 36 Figure 36. Dense urban fabric in Mazraa

Figure 37 .

 37 Figure 37. Medium density urban fabric in Ras Beirut Another area in Beirut was selected which shows the urban morphology of

Figure 38 .

 38 Figure 38. Dense informal urban fabric in Moussaytbeh

Figure 39 .

 39 Figure 39. a) Building constructed circa 1940s in Ras Beirut area with light-coloured facades with approximate albedo (α) of 0.7; b) Recently constructed building with light-coloured façade with approximate albedo of 0.7 (photographs taken by author)

Figure 41 .

 41 Figure 41. Newly constructed building with concrete rooftop in Beirut with approximate α of 0.225 (photograph taken by author)

  Beirut. There exist a few studies and reports related to climate changes and UHI in the existing literature for Beirut. One such report was prepared as part of Lebanon's Second National Communication on the assessment of future climate risks, vulnerability, and adaptation (MOE/UNDP/ELARD

Figure 42 .

 42 Figure 42. Vulnerability to UHI impacts in Beirut

Figure 43 .

 43 Figure 43. Schematic representation of the MOSES2 surface tile scheme representing land surfaces within a single model grid cell. Source: McCarthy, 2009; Report on CIRCE, urban heat island simulations

Figure 44 .

 44 Figure 44. Surface energy balance of the urban canopy model. Source.Best, et al. 2006, pp. 506

Figure 45 .

 45 Figure 45. Annual difference in UHI magnitude between three Mediterranean cities adapted from McCarthy, 2009; Report on CIRCE, urban heat island simulations Hence, McCarthy's simulations showed that Beirut exhibited the largest summer

Figure 46 .

 46 Figure 46. Surface temperatures dated 21 May 2000 at 8h12min courtesy of LANDSAT 7 ETM+

Figure 47 .

 47 Figure 47. Location of five weather stations within and outside of Beirut. Source: Google Earth, 2013

Figure 48

 48 Figure 48 below is a flow chart showing the elimination process carried out for

  Figure 49. Flow chart showing various steps taken in data collection process for Beirut

Figure 50 .

 50 Figure 50. Identification of building age groups in Beirut by extrapolation on ArcGIS of aerial images for the years 1971, 1998, 2008. Source (aerial images): Direction des Affairs Geographiques.

  the general information for roofs along with their respective thermal properties and here again reference is made to[START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] for α and ε values of the dominant roof materials as well as k and C.

Figure 51 .

 51 Figure 51. Classification of roof types in Beirut based on extrapolations on ArcGIS.

Figure 52 .

 52 Figure 52. Road classification into primary, secondary and tertiary roads by extrapolation using aerial image dated 2008. Source: Direction des Affairs Geographiques 6.3.3.6 Vegetation. Finally, for urban vegetation, all existing vegetation types,

Figure 53 .

 53 Figure 53. Ficus Nitida vegetation type typically found in Beirut garden/green areas and street trees with LAI of 2 (photographs taken by author)

Figure 55 .

 55 Figure 55. Selected cells for the purpose of distinct comparison of simulation results

Figure 56 .Figure 59 .

 5659 Figure 56. Canyon temperature simulations for the Control Run across Beirut on 01-February at 1200 UTC

Figure 61 .

 61 Figure 61. Evolution of surface roof temperatures for two selected cells on 01-July

Figure 63 .

 63 Figure 63. Roof temperature simulations for the Control Run across Beirut on 01-July at 1200 UTC

Figure 67 .

 67 Figure 67. Evolution of surface road temperatures for two selected cells on 01-February Figure 66. Evolution of surface road temperatures for two selected cells on 01-July

Figure 68 .Figure 71 .

 6871 Figure 68. Wall temperature for the Control Run across Beirut at midday on 01-February at 1200 UTC

Figure 73 .

 73 Figure 73. Temporal evolution of internal building temperatures for five selected cells at midday on 01-July

FigureFigure 75 .

 75 Figure75).

Figure 77 .

 77 Figure 77. Heating energy demand for Control Run across Beirut on 01-February at 2000 UTC

Figure 79 .Figure 82 .

 7982 Figure 79. Comparison of canyon temperatures between Scenario 1 and Control Run on 01-February

  272

Figure 91 .

 91 Figure 91. Comparison of canyon temperatures between Scenario 2 and Control Run on 01-July

Figure 96 .

 96 Figure 96. Comparison of wall temperatures between Scenario 2 and Control Run on 01-July

  The respective results were compared to those of the control run to assess the sensitivity of the model to modification of this specific parameter and the consequent impact on Beirut's urban microclimate. The results showed an increase in canyon temperatures of approximately 0.35 o C (or 3.65%) mainly during the early morning and late afternoon hours of the winter day but simulations were similar to the control run data throughout the rest of the day. During the summer day, canyon temperatures were again raised by 0.4 o C (or 1.25%) during the early morning and late afternoon hours of the day. This can be attributed to the low reflective properties of clear glass, where α=0.08 for clear glass with zenith angle less than 40 o and α=0.09-0.52 for clear glass with zenith angle 40 to 80 o

Figure 103 .

 103 Figure 103. Comparison of heating energy demand between Scenario 3 and Control Run on 01-July

Figure 106 .

 106 Figure 106. Comparison of heating energy demand between Scenario 5 and Control Run on 01-July

Figure 108 .

 108 Figure 108. Comparison of heating energy demand between Scenario 6 and Control Run on 01-July Figure 109. Comparison of cooling energy demand between Scenario 6 and Control Run on 01-Feb

  The city of Beirut covering approximately 21.47 km 2 is accordingly divided into cells of equal dimensions (200 x 200 m) across Beirut, where those cells that fall within the boundaries of the Mediterranean Sea are eliminated since this study focuses primarily on the town part of the city and its associated impacts on the UHI. Within each of these cells the urban characteristics comprised of building height, dominating façade, roofing and road materials along with their corresponding thicknesses, thermal and radiative properties, and vegetation types (whether high or low vegetation or bare soil) and their respective LAI values are defined. The urban boundary conditions are forced with meteorological records obtained from the Fanar weather station located approximately 3.5 km to the east of the Beirut administrative boundary in what is defined as a medium to dense urban fabric. This station is chosen due to the similarity of its location to the Beirut urban fabric, due to its relative proximity to the city as compared to the other existing weather stations spread out across the various regions of the country, and finally due to the continuity of the weather records.Simulations are accordingly run on TEB across Beirut for one entire year, with one hour time steps (or outputs at every hour). Comparisons are carried out for specified outputs like canyon temperatures or internal building temperatures and so on during February and July days, to determine the effects of existing urban characteristics on UHI during these different times of the year in Beirut in the view to recommend the most suitable mitigation action for alleviation of UHI from an urban planning and design perspective.

Figure 110 .

 110 Figure110. Solar radiation received in a canyon perpendicular to the sun direction; left hand: sun low over the horizon (λ > λ0); right hand: sun high over the horizon (λ < λ0). Source:Masson, 2000, pp.368

-

  Figure 111. Flow chart of first objective of this research

  planning system, which consists of the Urban Planning Law #69 for Lebanon dated 1983, the zoning specifications of Ecochard dated 1963 which was amended in the year 2007 with some minor modifications, and the Building Code or Construction Law #646 dated 2004.

  Finally, thermal standards for buildings in Lebanon were also established by the Ministry of Public Works and Transport (UNDP/GEF and MPWT/DGU 2005) based upon their respective climatic zones and an energy efficiency building code road map was also accordingly established for Lebanon (MED-ENEC/EU, 2012). Unfortunately these thermal standards for energy efficient buildings in Beirut have not yet been approved by the relevant authorities and have therefore not yet been adapted.

Figure 112 . 2014 Figure 113 .

 1122014113 Figure 112. Mexican researchers modeled significant cooling energy savings from cool roofs. Source: Akbari, 2014

Figure 114 .Figure 115 .

 114115 Figure 114. Recommended organization chart for the transfer of urban climatic knowledge amongst all parties involved in urban planning process in Beirut and institutional strengthening

  systems and standards. Categories of sustainability that can be incorporated into the existing Building Code #646 of Lebanon could potentially include planning and design, energy efficiency, and environmental quality dimensions. More specifically, elements of sustainability that could be incorporated into the Building Code #646 include orientation of buildings and their impact on energy consumption, natural daylight and view, insulations, green roofs, energy conservation measures, indoor environmental quality and coordination with the Environmental Law 444/2002 (LGBC, 2012). It is worth noting that although Law 444/2002 mentions the need to control and mitigate environmental degradation, it is actually the work plan prepared by the MOE for the period 2010-2012 which specifically mentions climate change and its importance at the urban scale (MOE/UNDP/ECODIT, 2011). Therefore, in this respect, reference should be made to both these documents.As such, changes in the Building Code #646 are necessary as there is a much needed alternative for advancing environmentally responsible architecture as can be seen in the numerous building rating systems developed worldwide like BREEAM (Building Research Establishment Environmental Assessment Methodology), LEED (Leadership in Energy and Environmental Design), and Estidama (the Arabic word for sustainability and the sustainability initiative of the Abu Dhabi Urban Planning Council), and so on. Upon looking into more detail regarding the workings of the Estidama rating system in Abu

Figure 116 .

 116 Figure 116. View of Sama Beirut Tower in Ashrafiyeh as well as five more high rises under construction as seen in the background (photograph taken by author)

Table 1 :

 1 Five weather types based on variations of wind speed cloud cover adapted from[START_REF] Alonso | Characteristics of the urban heat island in the city of Salamanca, Spain[END_REF] also generate urban heat or anthropogenic heat at the local scale which comes from many sources including car emissions, use of air-conditioning both in summer (for cooling) or winter (for heating), and industrial facilities(Che-Ani et al.,

	Weather Type	Mean daily wind	Cloudiness (C)
		speed (v) (km/h)
	Type I	v≤ 4	2/8 of cloudy sky
	Type II	v≤ 4	3/8 of cloudy sky
	Type III	4≤v≤22	2/8of cloudy sky
	Type IV	4≤v≤22	3/8 of cloudy sky
	Type V	v>22	For all cases of C

2.3.2 Urbanization and anthropogenic heat.

Increasing urban populations and associated urbanization and land use practices are taking their toll on the environment and its climate. According to the World Bank and the U.S. Central Bureau of Statistics, the global population is currently estimated at about 7 billion and it is expected to grow further to reach between 7.5 and 10.5 billion by year 2050. The United Nations World Urbanization Prospects Report

(2003)

expected that world population growth between 2000 and 2030 will happen in urban areas and that the world urban population is expected to rise by over 2 billion persons to reach 4.9 billion in 2030. With growing urban populations naturally vegetated and permeable surfaces become replaced with concrete impermeable urban surfaces thus expanding urbanization. Such changes are coupled with an ever-growing consumption of natural resources and burning of fossil fuels for power generation resulting in increasing air polluting emissions that contribute to the greenhouse gas (GHG) effect or climate change at the global scale. Human induced activities in cities

Table 2 :

 2 Albedo values for various urban surfaces according toNASA, 2012 and[START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF]

	Surface	Typical Albedo () Range
	Grass	0.25 -0.30
	Trees	0.15 -0.18
	Corrugated roof	0.10 -0.15
	Highly reflective roof	0.60 -0.70
	Colored paint	0.15 -0.35
	White paint	0.50 -0.90
	Tar and gravel	0.03 -0.18
	Red/brown tile	0.10 -0.35
	Brick/stone	0.20 -0.40
	Concrete	0.10 -0.35
	Asphalt	0.05 -0.20

2.3.4 Urban geometry.

Urban geometry is another important anthropogenic factor contributing to urban temperature variations

  Sky View Factor. Researchers often focus on an aspect of urban geometry called urban canyons which refer to relatively narrow streets lined by tall buildings. Urban canyons can have different effects on the UHI during the day time whereby the tall buildings can provide shading thus reducing temperatures while the incoming solar radiation that reaches inside the canyon is reflected and absorbed by the walls of buildings thus lowering the overall albedo of the city and accordingly raising the urban temperatures. During the night time, the buildings and other artificial man-made

surfaces in the urban canyon obstruct the heat being released thus generally impeding cooling effects. As previously mentioned, this research focuses on the UHI effect within the urban canyon in Beirut therefore it would potentially be interesting to investigate the effects of tall buildings on urban canyon temperatures as carried out and discussed in Chapter 7 of this thesis.

Table 3 .

 3 Description of three different urban patterns examined for optimal thermal conditions Source:

	Fahmy and Sharples, 2008
	Urban	Sites Description	Location
	Pattern No.
	#1	High density, compact, multi-family,	Central urban area northeast of
		low income apartment housing with a	metropolitan Cairo
		ground floor and four other floors
	#2	Mixed, clustered dot, multi-family,	Sheraton Heliopolis urban area
		high-income apartments with a	of metropolitan Cairo
		ground floor and three other floors
	#3	Dot single and multi-family high	Suburban area of metropolitan
		income villas and apartments with a	Cairo outside the first ring road
		ground floor and three other floors	of greater Cairo as part of new
			Cairo town
	2.3.5 Lack of vegetation. The landscape in rural areas is typically dominated by
	large vegetated surfaces or open spaces. Rural temperatures are therefore lower and
	cooler than their surrounding urban areas due to 1) shading provided by the trees and
	vegetation, and 2) the process of evapotranspiration in which plants release water from
	the earth's surface and accordingly dissipate ambient heat into the air thus helping to
	keep a city cool. In contrast, urban areas are characterized by dry, impermeable and dark
	mineralized surfaces consisting primarily of roofs, pavements, roads and parking lots that
	typically reflect less and absorb more of the sun's energy. As urbanization expands
	therefore, more vegetation is lost, and more surfaces become paved and covered with
	buildings thus resulting in lower levels of moisture and accordingly heat loss. Akbari,

3.2.2 Characteristics of the Urban Heat Island.

  Based on the existing literature, the urban heat island phenomenon is characterized by the following key features:

	 Higher air temperatures in urban areas in comparison to the surrounding
	semi-rural or rural areas;
	 Warmest urban temperatures after sunset and coolest temperatures after
	sunrise in urban areas in comparison to the surrounding semi-rural or rural
	areas;
	 More heat absorbing urban surface materials and less overall vegetative
	surfaces in urban areas in comparison to surrounding rural areas resulting in
	higher urban surface temperatures;
	 Under stable weather conditions (low/minimal wind speeds and clear skies)

Table 4 .

 4 UHI empirical generalizations adapted from[START_REF] Arnfield | Two decades of urban climate research: A review of turbulence, exchanges of energy and water, and the urban heat island[END_REF]

	Items Empirical generalization	Beirut case
	1	UHI intensity decreases with	Average day-time winter wind speed records of
		increasing wind speed	18-20m/s are typical for Beirut and are much less
			between 5-10m/s in summer. Average night-time
			winter wind speeds range between 13-20m/s
			while during the summer they range between 2-
			10m/s.
	2	UHI intensity decreases with	Cloud cover typically increases during the winter
		increasing cloud cover	season in Beirut
	3	UHI intensity is greatest	Anticyclonic events are not typical in Beirut
		during anticyclonic	Mediterranean climate
		conditions
	4	UHI intensity is best	This research investigates this specific
		developed in the summer or	characteristic of the UHI and finds that indeed
		warm half of the year	UHI intensity is best developed in the summer
			season (see Chapter 7 Numerical Analysis)
	5	UHI intensity tends to	At the beginning of the 20 th century Beirut surface
		increase with increasing city	area was at around 5 km 2 but due to rural exodus
		size and/or population	Beirut surface area grew to about 20 km 2 with a
			population density of approximately 21,000
			inhabitants/km 2 where artificial surfaces increased
			and UHI impacts also increased (see Chapters 5
			and 7)
	6	UHI intensity is greatest at	This research investigates this specific
		night	characteristic of the UHI and indeed finds that
			UHI intensity is greatest at night when trapped
			heat is released back into the atmosphere by the
			impermeable and low solar reflectivity surfaces
			(see Chapter 7 Numerical Analysis)
	7	UHI may disappear by day	This research investigates this characteristic of the
		or the city may be cooler	UHI but finds that areas with lower density urban
		than the rural environs	fabrics are typically cooler than dense urban
			fabrics because of the higher artificial and low
			solar reflectivity urban surfaces (see Chapter 7
			Numerical Analysis)

Table 5 .

 5 Limitations and advantages of various existing measurement types for UHI (prepared by author)

	Measurement	Limitations	Advantages	Examples of
	type			cities/countries of
				implementation
	Fixed and mobile	-time-consuming	-gives accurate	Athens, Greece
	weather stations	-weather-dependent	climatic data and	New York City,
		-can be quite costly	recent / new data	U.S.A.
		depending on the	-allows for the	Taiwan, China
		choice of instruments	choice of selection	Salamanca, Spain
		-requires good	for location of
		coordination amongst	weather stations or
		all involved parties	path to be taken in
			the case of mobile
			traverses
	High resolution	-they do not actually	-high quality, sharp	Chicago, IL,
	aerial-	measure UHI intensity	and finely detailed	Houston, TX,
	orthophotos	but rather help	-used to accurately	Sacramento, CA,
		determine areas that	characterize the area	and Salt Lake City,
		could benefit the most	fraction of various	UT, U.S.A.
		from UHI mitigation	surface types and	Mongkok., Hong
		strategies	vegetation fraction	Kong
			in cities
	Thermal remote	-thermal remote	-it is a fast process
	sensing	sensing is not able to	and therefore is
		capture the thermal	time efficient
		properties of tall	-gives indications of
		vertical surfaces and	the impact of
		facades such as trees	surface
		and buildings	temperatures on air
		-remotely sensed	temperatures and
		derived temperatures	accordingly UHI
		are surfaces	impacts
		temperatures of the
		emitting materials, and
		not air temperatures,
		hence can cause
		surface temperatures to
		exhibit a much greater
		spatial variation than
		the concurrent air
		temperatures

  . SOLENE is a modeling software which is used to simulate solar, luminous and thermal radiation parameters for urban and architectural spaces. It was developed by CERMA (Center for Methodological Research in Architecture) in Nantes in France and facilitates the evaluation of climatic designs in urban and architectural projects whereby simulations of the microclimatic solar fittings of buildings and other urban forms for example can be conducted (www.cerma.archi.fr/). SOLENE is therefore capable of simulating the influence of various choices of urban designs and urban architectural projects on the microclimate at the micro-scale or neighborhood scale and can accordingly provide some solutions to building designs and urban forms that can have least impacts on the microclimate.

  and radiative properties for urban surface parameters in its simulations within a grid cell and does not require detailed data (as in the case for the Finite Volume Model which is discussed in the subsequent section), and second because it takes into consideration surface-atmospheric energy exchanges at the city scale and not micro-scale or local-scale (see Chapter 6 of this thesis for more details on the elimination and accordingly selection process for TEB for the Beirut context).

	and investigations are
	continuously underway to improve the model by taking into consideration other relevant
	urban parameters characterizing a typical town or city. It is worth noting that TEB is
	being used widely in the field of urban climatology modeling and is even now
	incorporated in the French operational Numerical Weather Prediction (NWP) model

(www.cnrm.meteo.fr/). Compared to the other models thus far, TEB is the most suitable modeling scheme for the Beirut case because it is a simplified model that considers the dominant thermal

Table 6 .

 6 Summary of various different urban surface exchange modeling schemes (prepared by author)

	Urban surface	Characteristic / type	Specific features of modeling scheme	Reference
	exchange modeling	of modeling scheme
	schemes
	NARP-LUMPS (Net	Statistical model	-For small scale local studies	Grimmond and Oke, 2002
	All-Wave Radiation		-It is an urban meteorological parameterization	Hidalgo et al, 2008
	Parameterization /		scheme	Masson, 2006
	Local-scale Urban		-This model is adequate if observational field
	Meteorological Pre-		data are sufficient and well understood
	processing Scheme)		-Needs very few inputs
			-Computation is very efficient
			-Main weakness: only valid in the range of
			conditions observed in the field
	SM2-U	"Bulk" model or	-This model carries out simulations at the	Bozonnet et al, 2013
		simple model (as	micro-scale	www.ec-nantes.fr
		opposed to a "canopy"	-It represents an urban fragment extending	Mestayer, et al, 2004
		model)	from the street scale to a district composed of
			different types of surfaces including buildings,
			soil and vegetation with explicitly defined urban
			geometric parameters and relative positioning
	ENVI-met	Three-dimensional	-Simulates the surface-plant-air interactions in	www.envi-met.com
		numerical	urban environment with a typical resolution of	Ali-Toudert and Mayer, 2006
		microclimate model	0.5 m in space and 10 sec in time therefore it is	Bruse, 2004
			applied for micro-scale projects	Emmaunel & Fernando,
			-It requires few input data parameters	2007
			-It has the ability to reproduce major processes	Yu and Hien, 2006
			in the atmosphere that affect the microclimate	Bozonnet et al, 2013
			-It has high spatial and temporal resolution	Huttner and Bruse, 2009

-

Carries out simulations at the micro-scale

Table 7 .

 7 Description of various UHI mitigation strategies implemented and/or studied worldwide with successful results (prepared by author)

	Category of	Location of	Brief description of successful case study	References
	mitigation	case study
	measure

  This research discusses a mobile survey (via vehicles equipped with observation tubes consisting of temperature and datalogger) which was conducted to explore both the severity of UHI and cooling impacts of green areas in Singapore. Highest temperatures were measured in industrial areas and the airport which have less green areas compared with other land uses. Lowest temperatures were detectable in residential areas with more greenery indicating that within developments plants can cool the surroundings and generate lower ambient temperature. The study indicated the presence of UHI effect in Singapore with a maximum difference of 4.01 o C between planted areas and the central business district area and confirmed the cooling effect of green areas in Singapore.

	vegetation and/or	roofs	Oliveira, Andrade, and Vaz, 2011
	urban	green
	of
	Planting
		Singapore	-Wong and Yu, 2005

  This paper is a review aiming to present the actual state of the art on the development and assessment of cool materials for buildings and urban structures. Four categories of cool materials are assessed: 1) highly reflective and emissive light coloured materials; 2) cool coloured materials; 3) phase change materials; and, 4) dynamic cool materials. It is concluded that the wide use of cool materials can contribute significantly to the mitigation of the heat island effect and improvement of urban environmental quality. This paper presents the results of a comparative study aiming to investigate the suitability of paving materials to lower heat island effect. The study involved 93 commonly used paving materials outdoors and was performed during the summer period in 2001. The study therefore contributes to the selection of the most appropriate materials for outdoor urban applications that can help to combat the UHI.

		Not specific		Wong, et al., 2003 Doulous,
		to any one		Santamouris, and
		city or case		Livada, 2004
		study
	materials
	paving
	cool
	roofing and/or cool Using materials cool roofing paving and/or	city or case study Greece Not specific to any one Athens,	greater Athens area. The aim was to improve thermal comfort conditions, reduce the intensity of heat island, and improve the global use of reflective paving materials is a very efficient mitigation technique to improve thermal conditions in urban areas environmental quality in the considered area. It is concluded that the -Application of 4,500m 2 of reflective pavements in an urban park in the	Karlessi, 2011 Santamouris, Synnefa, and 2012 Santamouris, et al.,
	cool
	Using		-

--

  Cool communities' strategies were adopted for the city of L.A. which involved reroofing and repaving in lighter colours and planting shade trees that can effect substantial energy savings, both directly and indirectly. The analysis indicated that the L.A. heat island can be reduced by as much as 3Oc. Cooler roof and paving surfaces and 11 million trees which were planted should reduce ozone air pollution exceedence by 12% in L.A. and by slightly less in other smoggy cities. Iran -The densely populated city of Tehran is the area of concern; it is characterized by having high emissions of anthropogenic heat, low sky view factor, dominating concrete and asphalted surface areas which all play a significant role in exacerbating the UHI. For the mitigation of the UHI effect it is proposed to increase the albedo or solar reflectively of building materials, to place vegetation on buildings, to use green roofs and to also use cool roofs as these measures are seen to be the most effective solutions for lowering of UHI impacts. The study proposes that simple ways to cool the cities are the use of reflective surfaces (rooftops and pavements) and planting of urban vegetation and attempts to show it by illustrating case study examples in U.S. cities. On a large scale, evapotranspiration from vegetation and increased reflectin of incoming solar radiation by reflective surfaces will cool a community a few degrees in the summer. This study therefore suggests that heat island mitigation is an effective air pollution control strategy, more than paying for itself in cooling energy cost savings. This paper proposes to implement heat island mitigation strategies such as urban forestry, green roofs, and light surfaces for the city of New York. The paper therefore analyzes and models the UHI in New York city and tests the impacts of each of the aforementioned mitigation strategies on surface and near-surface temperatures in the city. It then evaluates the effects of the changes in land-surface cover in six case study area. the paper concludes that the mitigation strategies tested can reduce surface and near-surface air temperatures. Although street trees provide the greatest cooling potential per unit area, light surfaces provide the greatest overall cooling potential because there is more available area in which to implement this strategy compared to the other strategies.

		Bretz, Akbari, and Tehran, Che-Ani, et al., New York, Rosenzweig,
		NY	Rosenfeld, 1998 2009; Solecki, and
	Implementation of urban vegetation, green Implementation roofs and cool materials of urban Implementation of urban vegetation, vegetation, green roofs and green roofs and cool cool materials materials	U.S. cities including Los Angeles, CA; San Ramon, CA Los Angeles, CA Not specific study city or case to any one Not specific to any one city or case study	Akbari, Pomerantz, and Taha, 2001 Rosenfeld, Akbari, Romm, and Pomerantz, 1998 Akbari, 2005 Rizwan, Leung and Chunho, 2008 Shahmohamadi, Che-Ani, Etessam, Maulud, and Tawil, 2011 Slosberg, 2006

-Data were collected and analyzed from two U.S. cities where cool surfaces and shade trees were implemented to reduce energy use and to improve air quality in urban parks. The study showed that cool surfaces (cool roofs and cool pavements) and urban trees can have a substantial effect on urban air temperature and hence can reduce cooling-energy use and smog. 20% of national cooling demand can be avoided through large-scale implementation of heat-island mitigation measures.

-'

-This study was carried out to review and summarize various mitigating measures that are applied through an investigation of the most important feature of UHI. It is found that the heat re-radiated by the urban structures plays the most important role. Mitigating measures are categorized as: 1) related to reducing anthropogenic heat relase (e.g. by switching off air conditioners); 2) related to better roof design (e.g., green roofs, roof spray cooling, reflective roofs, etc.); 3) other design factors (e.g., humidification, increased albedo). It is also concluded that future research should be focused on design and planning parameters for reducing the effects of UHI.

---

Table 8 .

 8 Outline of history of urban planning of Beirut and respective environmental considerations (prepared by author)

	Period	Population Urbanization	Urban Planning/ Construction	Environmental Context
	Ottoman Period	80,000	-Flow of immigrants into	-1868 election of the first municipal	None
	(1840s-1920s)		Beirut due to political	council took place
			unrest in the country and	-First building code was
			the region	implemented by Beirut municipality
				known as the Defter Khan system
	French Mandate	200,000	-Political Arab refugees	Danger brothers drafted the first	None
	(1920-1943)		started traveling to Beirut	mater plan for Beirut city but this
			as well as locals for	was never implemented
			business opportunities
	Independent Era	900,000	-Urbanization sprawl and	-Ecochard drafted the first master	None
	(1943-1970s)		the creation of the	plan for Beirut in 1943 but this was
			"misery belts around the	never implemented.
			city center took place	-Ernst Egli's plan for the city was
			coupled with a rapid	approved in the 1950s which was
			demographic growth and	inspired by Ecochard's plans linking
			a massive rural to urban	the city to major highways leading
			migration	to Damascus, Sidon & Tripoli.
			-Influx of Palestinian	-In 1961, under the Fouad Chehab
			refugees in 1948 and the	Era (1958-1964), a new Planning
			establishment the refugee	Ministry was created, the first Town
			camps across Beirut	Planning law was passed in 1962,
			known as Shatila, and	and the GDUP and HCUP were
			Mar Elias	created.
				-A second master plan was drafted
				by Ecochard in 1963 which included
				Beirut Greater Area also
	Civil War Period	1,400,000	-Refugees, and rural	-In January of 1977, the Council for	-NEPA issuance in the U.S.A.
	(1970s to 1991)		migrants, in addition to	Reconstruction and Development	in 1969 and worldwide

Table 9 .

 9 Palestinian refugee camps in Beirut adapted fromFawaz and Peillen, 2002

	Name of	Year of	Population	Brief description
	Palestinian	establishment	of camp
	Refugee
	Camp
	Mar Elias	1952	1,411	Mar Elias is the smallest Palestinian refugee
				camp and covers approximately 5,400m 2 .
	Shatila	1949	12,235	Shatila was established by the International
				Committee of the Red Cross to
				accommodate the hundreds of refugees who
				poured into the area in 1948.

Table 10 .

 10 Environmental implications of Building Code #646adapted from MOE/UNDP/ECODIT, 2011

Table 11 .

 11 Key authorities and other non-governmental authorities involved in the urban planning process in Beirut

	Name of Authority	Responsibilities
	Beirut Municipality	• Permits for constructions in Beirut administrative area
		must be issued from the Municipality of Beirut and all
		ultimate decisions related to urban planning within the
		city are taken with the approval of the Municipality of
		Beirut
	Directorate General of	• DGUP develops urban regulations and coordinates
	Urban Planning	urban planning activities.
	(DGUP)	• It prepares and reviews urban master plans all over the
	(under the Ministry of	Lebanese territory except Beirut and Tripoli and three
	Public Works and	federations of municipalities (Jbail, Keserouan and
	Transport or MOPWT)	Metn) which have their own urban
		planning/engineering units.
		• It is involved in the building permit application
		process.
		• Urban master plans are either prepared by the DGUP or
		by a private urban planning office.
		• Completed master plans are submitted to the concerned
		municipality which has one month to respond.
		• If accepted, the plan is sent to COM for endorsement.
		• DGUP is also involved in the protection of
		archaeological and cultural heritage.
	Regional Departments	• Established in every caza to review construction
	of Urban Planning	permits and ensure compliance with urban planning
	(under the MOPWT)	regulations issued by DGUP and/or HCUP.
		• They are usually comprised of one director and several
		civil engineers (CE) or architects who assume
		responsibility for a specific area within the caza.
		• Regional departments act as technical advisor to local
		municipalities on urban planning and construction
		related matters.

-land use in Beirut.

  Having assessed the various urbanization development stages which helped shaped the urban form of Beirut within the context of UHI analysis the next step involves the assessment of the main land cover and land uses in Beirut from which the dominating urban surfaces and material compositions can be extrapolated. Thus, a visual assessment of the most recent aerial orthophoto of Beirut city

	NPMPLT or SDATL distinguishes four levels of land covers where level 4 is the more
	detailed and descriptive classification with over 20 subcategories (see Table 12). In
	general however, to identify directly the main categories of existing land covers, Level 1
	is referred to which classifies the existing land covers in Lebanon into 6 main categories
	as follows (see Figure 35):
	1. Territoire artificializé or urban or built environment (or built-up area);
	2. Territoire agricole or crop land or farm land;
	Lebanese Environment and Development Observatory (LED) and Management Support
	Consultant-Investment Planning Program (MSC-IPP Environment) dated June 2003. In
	this report, again four levels of land use-land cover types have been distinguished where
	Master Plan of the Lebanese Territory" (NPMPLT) or "Schéma Directeur level 4 is the most detailed of the four. Although this report does not identify the land
	d'Aménagement du Territoire Libanais" (SDATL) cover-land uses of Beirut city to the same detail as the NPMPLT, it does distinguish
	(http://www.cdr.gov.lb/study/SDATL/sdatlf.htm). This document was later endorsed by useful terminologies, which are referred to as necessary throughout this thesis.
	the Council of Ministers (COM) as Decree No. 2366 dated 20/06/2009 and is therefore an
	important document commonly referred to in the urban planning sector in Lebanon. The

(Department of Geographical Affairs, 2008)

showed that Beirut is primarily a dense built environment with extensive road networks. Figure

34

shows the built-up and predominantly artificial city of Beirut where roads and buildings cover the majority of the city's surfaces. In fact, the main land cover land uses in Beirut city include primarily buildings, roads, and asphalted spaces (which serve mainly as parking lots), with a lower fraction of vegetated surfaces. A land cover-land use study for Lebanon was carried out by DAR-IAURIF in the year 2004, as a project for the Council of Development and Reconstruction (CDR). The findings of this study are documented in what is referred to as the "National Physical 3. Surface boisée or forested areas; 4. Surface á végétation herbacée or rangeland; 5. Terrain naturel sans ou avec peu de végétation or natural land without or with little vegetation; 6. Surface en eau or water bodies.

According to the NPMPLT classification of land uses and land covers, Beirut is a predominantly artificial area (as per item 1 listed above). It is worth noting here that the NPMPLT of DAR-IAURIF is based on the land cover-land use report prepared by the

Table 12 .

 12 Land Use Classifications according to NPMPLT

	Level 1	Level 2	Level 3	Level 4
	-Urban or built-	-Area of activity	-Road infrastructure	-Highway
	up land	and infrastructure	-Discontinuous	-Urban sprawl
		-urbanized zone	urban fabric	-Vacant urban land
		-Urban or built up	-Urban sprawl	-Dense urban fabric
		land	-Vacant urban land	-Dense informal urban
		-Undeveloped	-Continuous urban	fabric -Moderately
		urban land	fabric	dense urban fabric
			-Industrial or	-Moderately dense
			commercial area	informal urban fabric
			-Port area	-Sparse urban fabric
			-Railway station	-Industrial or
			-Diverse sports and	commercial area
			leisure equipment	-Port area
			-Urban sprawl on	-Railway station
			sparse forest	-Diverse equipment
				-Diverse sports and
				leisure equipment
				-Archeological site
				-Tourist resort
				-Urban sprawl on
				sparse forest
	-Rangeland	-Artificial green	-Urban green space	-Urban green space
		area
	-Crop land or	-Intensive	-Intensive crops	-Intensive crop fields
	farm land	cultivation	fields	-Intensive protected
			-Intensive protected	crops (greenhouses)
			crops (greenhouses)
	-Water bodies	-Continental	-River or stream	-River or stream
		surface water	-Beach	-Beach
		-Beach	-Reclaimed sea	-Reclaimed sea
	-Forested areas -Sparse forest
	-Natural land	-Bare rock	-Bare rock	-Bare rock
	without or with	-Moderately	-Shrublands	-Shrublands
	little vegetation	dense herbaceous	-Moderately dense	-Moderately dense
		vegetation	herbaceous	herbaceous vegetation
			vegetation
	Source: CDR-NPMPLT /DAR-IAURIF, 2004

Source: MSC-IPP

Environment, 2003

Table 14 .

 14 Albedo (α) of dominating artificial urban surfaces in Beirut adapted from[START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] (prepared by author)

	Description of dominating	Material compositions	Albedo (α)
	urban surfaces in Beirut	in contact with ambient
		air
	Facades of buildings	Beige/white paint and	0.7
		plaster
	Rooftops	Grey concrete slab	0.225
	Roads	Asphalted road surfaces	0.2

Table 15 .

 15 Criteria for comparison of various available measurement tools

	Criteria		Measurement Types
		Fixed traverses	Mobile	Aerial	Thermal
			traverses	orthophotos	remote sensing
	Associated	High	High	Very high	Low
	costs
	Coordination	Required	Required	Required	Not applicable
	with authorities
	Permitting	Required	Required	Required	Required
	Availability of	Not available	Not available	Not available	Not available
	equipment
	Training	Not applicable	Not applicable Not applicable	Required
	requirements
	Timeline	Long	Long	Moderate	Not applicable
	Traffic	Expected	Expected	Not applicable Not applicable
	congestion
	Allocation of	Required	Required	Not applicable Not applicable
	set-up locations
	6.1

.1 Elimination process.

  Lebanon with the necessary equipment are not open for public use, not even for post-graduate students for that matter, as they generally are in the U.S.A. or other more advanced cities across Europe. Use of aircraft in Lebanon for such cases is restricted to military use. Finally, regarding thermal remote sensing data, according to the remote sensing department at the CNRS (National Council for Scientific Research or Conseil National de Recherches Scientifiques), the availability of the required data is not sufficient with many apparent gaps in data. Remote sensing data is typically obtained from LANDSAT or MODIS. Figure 46 is a LANDSAT image taken in May of 2000 at 08h12min showing relatively high surface temperatures, for this early time of the day, represented by yellow and red ranging from 33 to 47 o C in Beirut as opposed to the lower surface temperatures ranging from 18.5 to 30 o C represented by green in the suburban and rural areas to the east and south of Beirut city. It is expected that a thermal remote sensing image taken at

midday in Beirut would show much higher surface temperature records. Recent thermal images and data are unavailable, discontinuous, or unclear. It is also worth noting that thermal images provide data for surface temperatures as opposed to air temperatures and since this research is focused primarily on the latter this method for temperature measurements was eliminated.

Table 16 .

 16 Data on climatic stations within and outside Beirut administrative area

	Stations	Coordinates	Location	Years data	Applicability
			with	available
			respect to
			Beirut
	AUB old	x=35.480094	In Beirut 1875-1975	Recent records are not
	observatory	y=33.900581,			available however this
		z=25m			station was selected and
					climatic records were used
					to study historic weather
					patterns and relation to
					population growth -
	Fanar	x=35.55230556	3.5 km	2009-2012 This station was selected
		y=33.88411667	east of		and records were used for
		z=90m	Beirut		TEB atmospheric forcing
	Bir Hassan	x=35.49125278	1 km	2009-2012 Operation not continuous
		y=33.85714167	south of		and relevant records were
		z=40m	Beirut		not sufficient for analysis
					=> not selected
	Abdeh	x=35.98777778	60 km	2009-2012	Situated at a significant
		y=34.52083333	north of		distance from study area
		z=15m	Beirut		therefore not used for the
					purpose of this thesis =>
					not selected
	Rafik Hariri	x=35.4883	3 km
	International	y=33.8211	south of
	Airport	z=0	Beirut

Table 17 .

 17 Nature of data required to run TEB

	Cover	Description of data required for TEB cover fractions
	Type
		Walls	Internal	Roofs	Windows	Others
		Area of	Floors	Area of roofs;	Glass Ratio	Building
	Buildings	walls; number of layers; thicknesses; albedo; thermal	Internal floor layers; thicknesses; thermal conductivity; heat capacity	number of layers; thicknesses; albedo; thermal conductivity;	Glazing thermal Reflectance	height Total surface area of vertical (wall) surfaces
		conductivity;		heat capacity
		heat capacity
	Roads	Roads areas; number of layers; thicknesses, albedo; thermal conductivity; heat capacity; fraction of roads

Gardens

Type of vegetation: bare soil, low (NVEG) vegetation (LVEG) or high vegetation (LVEG); leaf area index (LAI) of different vegetation types; fraction of gardens Source:

[START_REF] Masson | A physically-based scheme for the urban energy budget in atmospheric models[END_REF] www.cnrm.meteo.fr/surfex-lab

Table 18 .

 18 Forcing / climatic data / files required for TEB/SURFEX and necessity for Beirut case

	Forcing file name Forcing file description	Units	Necessity for Beirut case
	Forc_DIR	Wind direction	Degrees	Required (obtained from
			from N,	Fanar weather station)
			clockwise
	Forc_DIR_SW	Direct short-wave	W/m 2
	Forc-LW Forc_PS Forc_QA Forc_SCA_SW	radiation Long-wave radiation Atmospheric pressure Atmospheric humidity Diffuse short-wave	W/m 2 Pa kg/kg W/m 2	Required and calculated with assistance from Valéry Masson Météo France
		radiation
	Forc-SNOW	Snow precipitation	kg/m 2 /s	Not required
	Forc_TA	Atmospheric temperature K	Required (obtained from
				Fanar weather station)
	Forc_WIND	Wind speed	m/s	Required (obtained from
				Fanar weather station)
	Forc_RAIN	Rain precipitation	kg/m 2 /s	Required (obtained from
				Fanar weather station)

Source: www.cnrm.meteo.fr/surfex-lab

6.3.2 Collected data for Beirut case. During the data collection process it was

Table 19 .

 19 Physical data collected for TEB analysis for Beirut from relevant authorities and institutions in Lebanon

	Names of Governmental Agencies Data Collected
	Direction des Affairs	Aerial image 2008, 15-20 cm pixel
	Geographiques	identifying number of floors for buildings in
		Beirut.
	Council for Development &	Land use classifications in Beirut
	Reconstruction (CDR)
	Central Administration of	Data on number of buildings in Beirut (2004)
	Statistics (CAS)
	Lebanese Agricultural Research Institute (LARI)	 Meteorological mean monthly records from the 5 weather stations for the period from 2009 to present:
		1. Ain el Abou
		2. Akoura
		3. Byr Hassan
		4. Ghazir
		5. Tarchich
		 Meteorological revords for Fanar station from
		the period 2000 to 2012.

Table 20 .

 20 Data on building wall layers in Beirut depending on building age group adapted fromOke (1987) (prepared by author)

	Buildi	Number	Description of wall	Thickness	Albedo (α) of	Emissivity (ε)
	ng	of wall	materials	of wall	first layer in	of first layer in
	Age	layers		materials	contact with	contact with
	Group			(cm)	ambient air	ambient air
	<1948	2	Beige/white paint and	4	0.7	0.9
			plaster
			Sandstone	17.5
	1948-	2	Beige/white paint and	4	0.7	0.9
	1970		plaster
			Hollow block/	17.5
			cementitious with
			sand and gravel
	1970-	2	Beige/white paint and	4	0.7	0.9
	1992		plaster
			Concrete masonry	20
			unit (CMU)
	>1992	5	Limestone	3	0.275	0.9
			White/beige paint	4
			and plaster
			Hollow block	15
			Plaster	0.05
			Natural stone	1.5

Table 21 .

 21 Building count in each age group (prepared by author)

	Beirut Districts	Before	1948-	1970-	1992-	Under	Total
		1948	1970	1992	Present	construction
	Ashrafieh		5,634	296	25	21	5,976
	Ain el Mreisse	6	959	85	67	6	1,123
	Bachoura		1,030	17	5	7	1,059
	Mazraa		6,923	737	107	53	7,820
	Medawar		882	336			1,218
	Minet el Hosn	1	517	60	26	27	631
	Moussaytbeh		5,459	598	54	64	6,175
	Port		2,48	23	44	7	322
	Ras Beirut	13	4,317	571	128	19	5,048
	Rmeil		3,132	73	13		3,218
	Saife	1	512	44	54	1	612
	Zoukak el Blatt		1,334	188	21	1	1,544
	Grand Total	21	30,947	3,028	544	206	34,746
	% Bldg. Stock	0.06% 89.1%	8.7%	1.56%	0.59%

Table 22 .

 22 Data on internal floor materials of buildings in Beirut based on age group category (prepared by author)

	Age-	Number of	Materials	Thicknesses	Heat	Thermal
	group	layers		(cm)	capacity	conductivity
	<1948	5	Concrete slab	35	0.28	0.08
			(aerated)	10
			Soft gravel	4	1.4	0.46
			Plaster	2.5
			Terrazzo	1.4	1.4	0.46
			Plaster
	1948-	5	Concrete slab	35	0.28	0.08
	1970		Soft gravel	10
			Plaster	4	1.4	0.46
			Terrazzo	2.5
			Plaster	1.4	1.4	0.46
	1970-	5	Concrete slab	30	0.28	0.08
	1992		Soft gravel	10
			Plaster	4	1.4	0.46
			Ceramic/marble/n	1.4	2.25	2.19
			atural
			stone/terrazzo	0.3	1.4	0.46
			Plaster
	1992-	5	Concrete slab	30	0.28	0.08
	present		Soft gravel	10
			Plaster	4	1.4	0.46
			Ceramic/marble/n	1.4	2.25	2.19
			atural
			stone/terrazzo	0.3	1.4	0.46
			Plaster
	6.3

.3.3 Windows. Data

on windows was also necessary to run simulations on TEB

Table 23 .

 23 Data regarding rooftops in Beirut adapted fromOke (1987) (prepared by author)

	Roof	Number of	Description	Thickness of	Albedo (α) of	Emissivity (ε)
	type	roof layers	of roof	roof	first layer in	of first layer in
			materials	materials	contact with	contact with
				(cm)	ambient air	ambient air
	Grey	1	Dense	20	0.225	0.805
			concrete
			roof slab
	White	2	White/white	0.15	0.7	0.9
			wash paint
			(insulation)
			Dense	20
			concrete
			roof slab
	Red-	3	Red clay	4.5	0.225	0.9
	tiled		tiles
			Polystyrene	3.5
			Dense	30
			concrete
			roof slab

6.3.3.5 Roads.

As for roads, three categories of roads were identified in Beirut

Table 24 .

 24 Sample grid cells in Moussaytbeh and Mazraa areas showing summation of town cover fractions

	Town Cover Fraction

Table 25 .

 25 Selected cells with contrasting cover fractions

Grid cell # Grid cell description of general land use / land cover and district Cover Fractions Total Building Garden Road

		7.1.
	1	American University of	0.28	0.61	0.11	1.00
		Beirut (AUB) in Ain El
		Mreisseh
	22	Port area predominantly	0.23	0.00	0.77	1.00
		with hangars
	220	Dense urban area Bachoura	0.32	0.12	0.56	1.00
	261	Seaside non-dense Ras	0.12	0.43	0.45	1.00
		Beirut
	439	Cemetery with gardens	0.02	0.73	0.25	1.00
		Mazraa (Horsch Beirut)

2 Selected outputs for the control run.

  The outputs of interest for the purpose of this research study were also selected as follows: The figures below(Figures 56 and 57) show the canyon temperature simulations across Beirut at 12:00hrs. when the incoming solar radiation is at its peak over Beirut, during both winter and summer seasons. Therefore, the temperature differential (ΔT) across Beirut is clearly marked in these figures, highlighting the areas of highest and lowest temperatures. Indeed the cells characterized by highest building fractions, like in Mazraa, Bachoura, and Ashrafiyeh areas for example, have higher temperatures inside the canyon. Lowest canyon temperature simulations are seen especially over the garden areas, such as "Horsh Beirut", toward the south of Beirut, the largest urban public garden in Beirut that covers approximately 0.375 km 2 or 1.75 % of the entire Beirut administrative area, thus showing the significant alleviating effects of these areas on the UHI. In February, or during the winter season, ΔT across Beirut is 2 o C, ranging from 15.9 to 17.3 o C, but this ΔT is much higher, at 6 o C, in July or during the summer, ranging from 37.6 in garden areas to 44.6 o C in high density

	7.1.2.1 Canyon Temperatures.
	 canyon temperatures,
	 surface rooftop temperatures,
	 surface road temperatures,
	 surface wall temperatures,
	 internal building temperatures,
	 cooling energy demands, and
	 heating energy demands.
	These output results are assessed and analyzed in more detail in the subsequent sections.

Table 26 .

 26 Devised scenarios run on TEB

	Scenarios	Description
	Scenario 1	Albedo of roofs increased to 0.7 (previously α=0.2)
		in all grid cells across Beirut
	Scenario 2	Albedo of roads increased to 0.8 (previously α
		=0.225)
	Scenario 3

Table 28 .

 28 Summary of results for the devised scenarios and their suitability for the Beirut context

	Scenarios	Suitability for Beirut case
	Scenario 1	Increasing the albedo of roof surfaces reduced canyon temperatures
		especially during the summer season thus lowering overall cooling
		energy demands -> suitable mitigation strategy for Beirut
	Scenario 2	Increasing the albedo of road surfaces reduced canyon temperatures
		during the summer but raised the wall temperatures and internal
		building temperatures accordingly raising cooling energy demands
		significantly -> not a suitable mitigation strategy for Beirut
	Scenario 3	Increasing the glass ratio of buildings significantly affected the
		canyon temperatures, internal building temperatures and cooling
		energy demands -> not a suitable mitigation strategy for Beirut
	Scenario 4	Increasing building heights increased canyon temperatures and
		cooling energy demands -> not a suitable mitigation strategy for
		Beirut
	Scenario 5	Increasing heights of vegetation reduced canyon temperatures
		during winter and summer but this approach would require removal
		and replacement with new tree types which might not necessarily
		easily adapt to Beirut's Mediterranean climate -> not a suitable
		mitigation strategy for Beirut
	Scenario 6

  Throughout the history of architectural design, engineering, infrastructure, transportation, urban design, and urban policies of Beirut and Lebanon, available literature shows that very little consideration has been given to protection of the environment whether at national or city scale level[START_REF] Fawaz | Urban planning in Lebanon[END_REF] Rowe, P.G. & Sarkis, H, 1998) (Table8). In fact, according to the latest report on the state of the environment of Lebanon, Beirut and its immediate surroundings have been and continue to be experiencing haphazard or uncontrolled planning which are

	accordingly having irreversible effects on the surrounding environment including climate
	(MOE/UNDP/ECODIT, 2011). Considering the unstable political situation of the country
	this is understandable however upon closer examination it is found that such negative
	effects are further aggravated as a result of deficiencies in the existing legislations,
	policies and regulations, and weak institutional and administrative frameworks.

Table 29

 29 below. These directives are generally geared toward the protection of the environment, natural landscapes and sites and do not specifically mention consideration or protection of the urban microclimate. Due to a lack of reinforcement and reporting regime, unfortunately such considerations are often overlooked by the governing authorities. This could be attributed to the fact that these institutions are generally understaffed and/or do not have skilled personnel; this is typical in governing agencies across Lebanon and is primarily due to the low associated salaries. In addition, there is no direct or efficient coordination between the aforementioned authorities concerned with the urban planning process of Lebanon and the Ministry of Environment (MOE), which is responsible for all issues pertaining to the environment and climate in Lebanon as per Environmental Law 444/2002 (see Appendix VI). Moreover, coordination with the Municipality of Beirut, the key authority in charge of all permitting issues for building constructions, urban planning and so on, is limited.

Table 29 .

 29 Summary of assessment of environmental and urban microclimatic considerations in urban planning context of Beirut

	Legal documents,	Assessment of environmental and urban microclimatic
	institutional	considerations
	framework and urban
	planning developers in
	Beirut
	Urban Planning Law #69	Considers the environmental dimension to a certain extent in
	(1983)	several articles 7, 8, 9, 17, 19, 20, 23 & 24. These directives
		are generally geared toward protection of the environment,
		natural landscapes and sites but there is no mention of
		protection of the urban microclimate. Also, due to a lack of
		reinforcement and reporting regime, such considerations are
		often overlooked by the governing authorities
	Building code #646

Table 30 .

 30 Environmental dimensions considered within the Urban Planning Law #69 (dated 1983) and corresponding weaknesses and opportunities in terms of climatic issues

	Article # Directive	Weaknesses and Opportunities
	7	Urban planning should consider the	There is very little or no evidence for
		relationship between communities	sustainable development taking place
		and surrounding areas including	within the Beirut context although
		agricultural areas, forested areas, and	major attempts and works are being
		the protection of the environment	carried out toward achieving this
		and to consider the use of the land	goal as per "1 er atelier urbain vers
		for the benefit of the public good	une politique d'aménagement
		aiming toward achieving sustainable	durable des espaces publics de
		development	Beyrouth" (www.bt-villes.org). It is
			recommended to modify Article 7 to
			include also protection of the
			climate aiming toward achieving
			sustainable development.
	8	Urban master plans must specify the
		criteria for land use by taking into
		consideration the agricultural value
		of the land and the possibility or
		implementation of irrigation canals.

Table 31 .

 31 Recommendations for modifications of the Building Code #646 (dated 2004) of Lebanon

	Requirements	Description of requirements Actions
	Increase solar reflectivity	All rooftops in Beirut must	Cool roof materials include
	of rooftops	have albedo values 0.6-0.8	white-coloured paint or
			limestone paint
	Increase solar reflectivity	All facades in Beirut must	Cool facades include
	of facades	have albedo values > 0.7	white/beige paint or plaster
	Decrease glass ratio	All buildings in Beirut must	Building designs should
		have glass ratio < 0.4 (40%)	ensure that while buildings
			are properly ventilated and
			have natural lighting they
			should not have glass ratios
			>40%
	Height of buildings	All buildings in Beirut must	More stringent efforts
		have heights not more than	should be made to abide by
		twice the width of roads on	the maximum permissible
		which they will be built and	height for buildings and
		should strictly comply with	leniency should not be
		Building Code #646	permitted unless the
		requirements (Appendix IV)	building can be classified as
			a green building following a
			specific rating system like
			Arz for example
	Landscaping / vegetation	All buildings must ensure	Landscape architects and
	around buildings	planting of one row of urban	urban planners must
		trees (preferably pine trees or	coordinate to ensure
		ficus nitida) around the	maximizing garden areas
		building perimeter	around building perimeter

Except in Australia, the authorities use a minimum urban density definition of 400 persons per square kilometer (Demographia World Urban Areas,

2015)2 Suburban area refers to an area lying immediately outside of a city or a town, especially a smaller residential community

Built-up areas or a built environment is a human-made landscape, as distinguished from the natural environment. It is a material, spatial and cultural product made by man that combines physical elements and energy in forms of living, working and playing. It has been defined as "the human-made space in which people live, work, and recreate on a day-to-day basis"[START_REF] Roof | Public Health: Seattle and King County's push for the built environment[END_REF].

Artificial surfaces infer impermeable man-made surfaces common in urbanized areas as opposed to natural areas covered by vegetation and which are accordingly permeable

A "tall building" is a multi-story structure in which most occupants depend on elevators to reach their destinations. The most prominent tall buildings are called 'high-rise buildings 'in most countries. A highrise building can be defined as follows: 1) "Any structure where the height can have a serious impact on evacuation"; 2) "For most purposes, the cut-off point for high-rise buildings is around seven stories. Sometimes, seven stories or higher define a high-rise, and sometimes the definition is more than seven stories. Sometimes, the definition is stated in terms of linear height (feet or meters) rather than stories[START_REF] Craighead | High-rise security and fire life safety[END_REF]. For the purpose of this research, a similar definition for a "tall building" having seven stories is applied.

NDVI or Normalized Difference Vegetation Index (NDVI) is a numerical indicator that uses the visible and near-infrared bands of the electromagnetic spectrum and is adopted to analyze remote sensing measurements and assess whether the target being observed contains live green vegetation or not.

The Greater Beirut Area (GBA) which is generally identified by planners as such, extends between the rivers of Damour and Nahr el-Kalb (or between the Dbayeh and Hadath areas), therefore lying outside Beirut administrative boundary, although there is no official jurisdiction of public recognized boundaries for this metropolitan area[START_REF] Fawaz | Informal urban development/the Lebanese experience/brief overview[END_REF].

The Monin-Obukhov length is used to describe the effects of buoyancy on turbulent flows, particularly in the lower tenth of the atmospheric boundary layer.

Mohafaza means "governorate" or "region"

Caza means "district" which falls within a governorate boundary

Public domain is State owned land and protection consists of forbidding construction, quarries, cutting of trees, and grazing (CDR-NPMPLT /DAR-IAURIF, 2004)

It is worth noting that within the context of this thesis and with respect to radiation properties (namely albedo[α] and emissivity (ε)) and thermal properties (mainly heat capacity and thermal conductivity) of urban materials, reference is made primarily to[START_REF] Oke | Boundary Layer Climates. 2nd Edition[END_REF] as this is the most comprehensive and reliable source of information in this respect and has indeed been referred to in numerous studies on UHI analysis(Akbari, 2001; Montavez, et al., 2008;[START_REF] Taha | Urban climates and heat islands: albedo, evapotranspiration, and anthropogenic heat[END_REF].

These studies were developed within the context of Project "Capacity Building for the adoption and application of Thermal Standards for Buildings", again falling under the topic of "Climate Change", and aiming at the establishment of thermal standards for buildings.

This research does not aim to investigate the specific number of buildings that are demolished and replaced by new buildings although the total number of buildings that are being constructed within each cadastral area of Beirut is determined via Google Earth satellite imagery (see Table21)

In this research, there are a total of 446 cells of 200 x 200m dimensions across Beirut in which simulations using TEB are run. These were prepped using ArcGIS software and the most recent aerial image dated 2008.

The Marina Towers is a residential complex in Beirut Central District and is built on over 7,000m2 of land with the main tower reaching a height of 150m.

Sama Beirut is an upcoming residential, commercial and office tower in the Sodeco region of Ashrafiyeh in Beirut. It is a 50-storey high-rise with a height of approximately 187m.

Acknowledgements

Abbreviations

Population of Beirut City

Urban population growth directly impacts the surrounding environment and microclimate [START_REF] Mccarthy | Climate change in cities due to global warming and urban effects[END_REF]. Data for population figures prior to the 1800s for Beirut is sparse or not available. However, available data after the 1800s shows that population figures in the capital city soared during this period for many reasons but mainly due to instability in the region and business opportunities. Lebanon's last population census was conducted in 1932 and since then all population estimates have been based on surveys and extrapolations (MOE/UNDP/ECODIT, 2011). Lebanon's resident population was 3.7 million in the year 2007, excluding an estimated 425,000

Palestinian refugees (CAS, 2008;UNRWA, 2008). The total population in 2008 including refugees was therefore about 4.2 million. As for Beirut city, the population was at about 400,000 in 2007 (CAS, 2008).

According to Yassin (2012), Lebanon witnessed a gradual population growth from 1896 to 2005 with a distinctive rise in its capital city of Beirut. Figure 27 is an illustration of this population rise in Beirut in comparison to the country's overall population growth. When this population growth in Beirut is correlated against maximum and minimum temperature trends it is found that there is a very strong positive correlation between these two parameters with an R 2 value of 0.97 (see Figure 28). This rural exodus continues to present day and is in part attributed to greater job opportunities, improved and better municipal services as well as wider choices for education within the capital city of Beirut.

As such, rural exodus can have potentially significant impacts on the surrounding environment and specifically the UHI due to a greater demand for housing needs,

Legal and institutional urban planning framework of Lebanon. Strategic

urban planning is very important in ensuring sustainable utilisation of land available in urban areas and in minimizing degradation of the environment. This section therefore gives an outline of the legal urban planning framework of Lebanon comprised of the Urban Planning Law #69 and the Building Code #646. The various parties involved in the institutional framework for urban planning in Lebanon are also outlined. The aim of this section is to identify any weaknesses and opportunities for potential improvements in the existing Urban Planning Law #69 and Building Code #646 of Lebanon and to identify the key players who can make this difference.

Urban Planning Law #69

The Urban Planning Law of Lebanon, Law No. 69, was issued in September of 1983 further to modifications of the previous Urban Planning Law of July 24 1962 (see Appendix III for a full copy of Urban Planning Law 69/1983 in Arabic). It is under this law that Lebanon functions today. Although drafted and approved during a period of great civil unrest and political insecurity in the country, the new modified Law took into consideration the environmental discipline in several of its directives as detailed below (MOE/UNDP/ECODIT, 2011):

-Article 7: urban planning should consider the relationship between communities and surrounding areas including agricultural areas, forested areas, and the protection of the environment.

-Article 8: Urban master plans must specify the criteria for land use by taking into consideration the agricultural value of the land and the possibility or implementation of irrigation canals. These should be specified prior to In addition, the emissivity of the ground (subscript g) and the surface (s) are assumed to be 1. The terms Q H and Q E are the turbulent sensible and latent heat fluxes respectively, and Q G is the energy exchange between the canopy and the underlying soil.

There are relatively few parameters used for the urban tile and these include surface albedo, aerodynamic roughness length, and heat capacity (as opposed to TEB which considers many more parameters as highlighted later). In addition the urban surface is considered impermeable, increasing surface runoff, and limiting evaporation to water lying on the surface following precipitation. If the urban surface is dry there is no evaporation. It is also worth noting that the model contains no information about the true morphology of cities, and the tile scheme cannot describe the spatial distribution of different surface types within a grid cell.

Therefore, although this tiled scheme is somewhat similar to the TEB scheme, which is selected as the most suitable model for conducting UHI analysis for the Beirut case as discussed in more detail in Chapter 6 of this thesis, in that they are both tiled schemes and function on the basis of the surface energy exchange equation, it is in fact a much simpler model which does not consider the energy exchange between the main urban surfaces that characterize the city such as walls, rooftops and roads(as considered in TEB) and in addition it does not consider important urban parameters like heat conductivity or emissivity of these urban surfaces, not to mention that it is based on a much larger regional scale of study. Moreover, it is worth noting that the model aimed to replicate the results of previous studies conducted for characterization of urban heat island as in the case of the city of Athens for example [START_REF] Kassomenos | Mesoscale and macroscale aspects of the morning Urban Heat Island around Athens, Greece[END_REF].

Furthermore, the model assumed that the Mediterranean region has low soil moisture the nature of data required to run the simulations on TEB and after having obtained relevant data from various governmental authorities and academic institutions in Lebanon depending on their availability, the data that was still missing was identified. This included for example data urban geometric parameters as well as material compositions which are necessary to run the urban heat island simulations on TEB. After consulting with the Central Administration of Statistics (CAS), the authority in charge of collecting and gathering all data and statistics of this nature in Lebanon, it was discovered that although this type of data is not available at present time, a campaign for collection and digitization of this type of data on buildings is being planned for the near future.

PART IV: UHI IN BEIRUT

Deficiency of this type of data was further confirmed by consulting with the Order of Engineers and Architects. As for the roads and vegetation parameters, again data was found to be limited. Therefore by meeting with concerned authorities, consulting with the relevant experts, conducting site visits and using the general available information from satellite and aerial images, the required data was collected and compiled and prepped to run simulations on TEB although it is worth noting that since absolute values were not was increased from 0.225 to 0.8 to assess the impact of "cool" road surface materials on the UHI effect of Beirut city as such since this is another commonly implemented mitigation strategy in other similar dense cities [START_REF] Santamouris | Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions[END_REF]. Again, as for the previous scenario 1, the outputs selected for these simulation runs included canyon temperatures, roof temperatures, road temperatures, wall temperatures, internal building temperatures, and cooling and energy demands (see Figures 90 to 101).

There were no significant impacts observed in canyon temperature results during the winter however during the summer canyon temperatures were reduced by approximately 0.7%. For surface road temperatures, significant changes were observed where road temperatures were reduced by 2.5 o C (or 14%) during the winter and much more at 25 o C (or 36%) during the summer emphasizing the important cooling effect of road surfaces upon increasing its albedo properties. As for roof temperatures however, an approximate 2% increase in simulations was observed during the winter and about a 1% increase during the summer; this could be attributed to the higher reflective properties of the roads and their potential direct effects on the facades and roofs of the buildings inside the canyon thus raising their respective temperatures. Regarding wall temperatures again the existing institutional frameworks to ensure a rigorous implementation of green and sustainable urban planning and design practices in Lebanon. In addition, there still remains an important need to consider the urban microclimatic factor in the urban planning and design policies.