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Precipitation

In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation; their water vapor does not condense sufficiently to precipitate, so fog and mist do not fall. (Such a non-precipitating combination is a colloid.) Two processes, possibly acting together, can lead to air becoming saturated with water vapor: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.

Moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed by the low temperature into clouds and rain. This process is typically active when freezing rain occurs. A stationary front is often present near the area of freezing rain and serves as the focus for forcing moist air to rise. Provided there is necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely nimbostratus and cumulonimbus if significant precipitation is involved. Eventually, the cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation occurs within the tropics and is caused by convection. The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah regions.

Precipitation is a major component of the water cycle, and is responsible for depositing fresh water on the planet. Approximately 505000 km3 of water falls as precipitation each year: 398000 km3 over oceans and 107000 km3 over land. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 mm, but over land it is only 715 mm. Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Global warming is already causing changes to weather, increasing precipitation in some geographies, and reducing it in others, resulting in additional extreme weather.

Precipitation may occur on other celestial bodies. Saturn's largest satellite, Titan, hosts methane precipitation as a slow-falling drizzle, which has been observed as Rain puddles at its equator and polar regions.

Types
Precipitation is a major component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km3 of water falls as precipitation each year, 398,000 km3 of it over the oceans. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 mm.

Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall. Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Mixtures of different types of precipitation, including types in different categories, can fall simultaneously. Liquid forms of precipitation include rain and drizzle. Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle". Frozen forms of precipitation include snow, ice needles, ice pellets, hail, and graupel.

Measurement

 * Liquid precipitation: Rainfall (including drizzle and rain) is usually measured using a rain gauge and expressed in units of millimeters (mm) of height or depth. Equivalently, it can be expressed as a physical quantity with dimension of volume of water per collection area, in units of liters per square meter (L/m2); as 1L=1dm3=1mm·m2, the units of area (m2) cancel out, resulting in simply "mm". This also corresponds to an area density expressed in kg/m2, if assuming that 1 liter of water has a mass of 1 kg (water density), which is acceptable for most practical purposes. The corresponding English unit used is usually inches. In Australia before metrication, rainfall was also measured in "points", each of which was defined as one-hundredth of an inch.

 * Solid precipitation: A snow gauge is usually used to measure the amount of solid precipitation. Snowfall is usually measured in centimeters by letting snow fall into a container and then measure the height. The snow can then optionally be melted to obtain a water equivalent measurement in millimeters like for liquid precipitation. The relationship between snow height and water equivalent depends on the water content of the snow; the water equivalent can thus only provide a rough estimate of snow depth. Other forms of solid precipitation, such as snow pellets and hail or even sleet (rain and snow mixed), can also be melted and measured as their respective water equivalents, usually expressed in millimeters as for liquid precipitation.

Cooling air to its dew point
The dew point is the temperature to which a parcel of air must be cooled in order to become saturated, and (unless super-saturation occurs) condenses to water. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. The cloud condensation nuclei concentration will determine the cloud microphysics. An elevated portion of a frontal zone forces broad areas of lift, which form cloud decks such as altostratus or cirrostratus. Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions.

There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, and evaporative cooling. Adiabatic cooling occurs when air rises and expands. The air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain (orographic lift). Conductive cooling occurs when the air comes into contact with a colder surface, usually by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation.

Adding moisture to the air
The main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, cool or dry air moving over warmer water, and lifting air over mountains.

Raindrops
Coalescence occurs when water droplets fuse to create larger water droplets, or when water droplets freeze onto an ice crystal, which is known as the Bergeron process. The fall rate of very small droplets is negligible, hence clouds do not fall out of the sky; precipitation will only occur when these coalesce into larger drops. droplets with different size will have different terminal velocity that cause droplets collision and producing larger droplets, Turbulence will enhance the collision process. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain.

Raindrops have sizes ranging from 5.1 to 20 mm mean diameter, above which they tend to break up. Smaller drops are called cloud droplets, and their shape is spherical. As a raindrop increases in size, its shape becomes more oblate, with its largest cross-section facing the oncoming airflow. Contrary to the cartoon pictures of raindrops, their shape does not resemble a teardrop. Intensity and duration of rainfall are usually inversely related, i.e., high intensity storms are likely to be of short duration and low intensity storms can have a long duration. Rain drops associated with melting hail tend to be larger than other rain drops. The METAR code for rain is RA, while the coding for rain showers is SHRA.

Ice pellets
Ice pellets or sleet are a form of precipitation consisting of small, translucent balls of ice. Ice pellets are usually (but not always) smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL.

Ice pellets form when a layer of above-freezing air exists with sub-freezing air both above and below. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A temperature profile showing a warm layer above the ground is most likely to be found in advance of a warm front during the cold season, but can occasionally be found behind a passing cold front.

Hail

Like other precipitation, hail forms in storm clouds when supercooled water droplets freeze on contact with condensation nuclei, such as dust or dirt. The storm's updraft blows the hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted again. Hail has a diameter of 5 mm or more. Within METAR code, GR is used to indicate larger hail, of a diameter of at least 6.4 mm. GR is derived from the French word grêle. Smaller-sized hail, as well as snow pellets, use the coding of GS, which is short for the French word grésil. Stones just larger than golf ball-sized are one of the most frequently reported hail sizes. Hailstones can grow to 15 cm and weigh more than 500 g. In large hailstones, latent heat released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud.

Snowflakes
Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze. Once a droplet has frozen, it grows in the supersaturated environment. Because water droplets are more numerous than the ice crystals the crystals are able to grow to hundreds of micrometers in size at the expense of the water droplets. This process is known as the Wegener–Bergeron–Findeisen process. The corresponding depletion of water vapor causes the droplets to evaporate, meaning that the ice crystals grow at the droplets' expense. These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their mass, and may collide and stick together in clusters, or aggregates. These aggregates are snowflakes, and are usually the type of ice particle that falls to the ground. Guinness World Records list the world's largest snowflakes as those of January 1887 at Fort Keogh, Montana; allegedly one measured 38 cm wide. The exact details of the sticking mechanism remain a subject of research.

Although the ice is clear, scattering of light by the crystal facets and hollows/imperfections mean that the crystals often appear white in color due to diffuse reflection of the whole spectrum of light by the small ice particles. The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed. Rarely, at a temperature of around -2 C, snowflakes can form in threefold symmetry—triangular snowflakes. The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing. No two snowflakes are alike, as they grow at different rates and in different patterns depending on the changing temperature and humidity within the atmosphere through which they fall on their way to the ground. The METAR code for snow is SN, while snow showers are coded SHSN.

Diamond dust
Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching -40 C due to air with slightly higher moisture from aloft mixing with colder, surface-based air. They are made of simple ice crystals, hexagonal in shape. The METAR identifier for diamond dust within international hourly weather reports is IC.

Occult deposition
Occult deposition occurs when mist or air that is highly saturated with water vapour interacts with the leaves of trees or shrubs it passes over.

Frontal activity
Stratiform or dynamic precipitation occurs as a consequence of slow ascent of air in synoptic systems (on the order of cm/s), such as over surface cold fronts, and over and ahead of warm fronts. Similar ascent is seen around tropical cyclones outside of the eyewall, and in comma-head precipitation patterns around mid-latitude cyclones. A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a drying of the air mass. Occluded fronts usually form around mature low-pressure areas. Precipitation may occur on celestial bodies other than Earth. When it gets cold, Mars has precipitation that most likely takes the form of ice needles, rather than rain or snow.

Convection
Convective rain, or showery precipitation, occurs from convective clouds, e.g. cumulonimbus or cumulus congestus. It falls as showers with rapidly changing intensity. Convective precipitation falls over a certain area for a relatively short time, as convective clouds have limited horizontal extent. Most precipitation in the tropics appears to be convective; however, it has been suggested that stratiform precipitation also occurs. Graupel and hail indicate convection. In mid-latitudes, convective precipitation is intermittent and often associated with baroclinic boundaries such as cold fronts, squall lines, and warm fronts. Convective precipitation mostly consist of mesoscale convective systems and they produce torrential rainfalls with thunderstorms, wind damages, and other forms of severe weather events.

Orographic effects
Orographic precipitation occurs on the windward (upwind) side of mountains and is caused by the rising air motion of a large-scale flow of moist air across the mountain ridge, resulting in adiabatic cooling and condensation. In mountainous parts of the world subjected to relatively consistent winds (for example, the trade winds), a more moist climate usually prevails on the windward side of a mountain than on the leeward or downwind side. Moisture is removed by orographic lift, leaving drier air (see katabatic wind) on the descending and generally warming, leeward side where a rain shadow is observed.

In Hawaii, Mount Waiʻaleʻale, on the island of Kauai, is notable for its extreme rainfall, as it has the second-highest average annual rainfall on Earth, with 460 in. Storm systems affect the state with heavy rains between October and March. Local climates vary considerably on each island due to their topography, divisible into windward (Koolau) and leeward (Kona) regions based upon location relative to the higher mountains. Windward sides face the east to northeast trade winds and receive much more rainfall; leeward sides are drier and sunnier, with less rain and less cloud cover.

In South America, the Andes mountain range blocks Pacific moisture that arrives in that continent, resulting in a desertlike climate just downwind across western Argentina. The Sierra Nevada range creates the same effect in North America forming the Great Basin and Mojave Deserts. Similarly, in Asia, the Himalaya mountains create an obstacle to monsoons which leads to extremely high precipitation on the southern side and lower precipitation levels on the northern side.

Snow
Extratropical cyclones can bring cold and dangerous conditions with heavy rain and snow with winds exceeding 119 km/h, (sometimes referred to as windstorms in Europe). The band of precipitation that is associated with their warm front is often extensive, forced by weak upward vertical motion of air over the frontal boundary which condenses as it cools and produces precipitation within an elongated band, which is wide and stratiform, meaning falling out of nimbostratus clouds. When moist air tries to dislodge an arctic air mass, overrunning snow can result within the poleward side of the elongated precipitation band. In the Northern Hemisphere, poleward is towards the North Pole, or north. Within the Southern Hemisphere, poleward is towards the South Pole, or south.

Southwest of extratropical cyclones, curved cyclonic flow bringing cold air across the relatively warm water bodies can lead to narrow lake-effect snow bands. Those bands bring strong localized snowfall which can be understood as follows: Large water bodies such as lakes efficiently store heat that results in significant temperature differences (larger than 13 °C or 23 °F) between the water surface and the air above. Because of this temperature difference, warmth and moisture are transported upward, condensing into vertically oriented clouds (see satellite picture) which produce snow showers. The temperature decrease with height and cloud depth are directly affected by both the water temperature and the large-scale environment. The stronger the temperature decrease with height, the deeper the clouds get, and the greater the precipitation rate becomes.

In mountainous areas, heavy snowfall accumulates when air is forced to ascend the mountains and squeeze out precipitation along their windward slopes, which in cold conditions, falls in the form of snow. Because of the ruggedness of terrain, forecasting the location of heavy snowfall remains a significant challenge.

Within the tropics
The wet, or rainy, season is the time of year, covering one or more months, when most of the average annual rainfall in a region falls. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics. Savanna climates and areas with monsoon regimes have wet summers and dry winters. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is equally distributed through the year. Some areas with pronounced rainy seasons will see a break in rainfall mid-season when the intertropical convergence zone or monsoon trough move poleward of their location during the middle of the warm season. When the wet season occurs during the warm season, or summer, rain falls mainly during the late afternoon and early evening hours. The wet season is a time when air quality improves, freshwater quality improves, and vegetation grows significantly. Soil nutrients diminish and erosion increases. Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wet season.

Tropical cyclones, a source of very heavy rainfall, consist of large air masses several hundred miles across with low pressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southern hemisphere) or counterclockwise (northern hemisphere). Although cyclones can take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions. Areas in their path can receive a year's worth of rainfall from a tropical cyclone passage.

Large-scale geographical distribution
On the large scale, the highest precipitation amounts outside topography fall in the tropics, closely tied to the Intertropical Convergence Zone, itself the ascending branch of the Hadley cell. Mountainous locales near the equator in Colombia are amongst the wettest places on Earth. North and south of this are regions of descending air that form subtropical ridges where precipitation is low; the land surface underneath these ridges is usually arid, and these regions make up most of the Earth's deserts. An exception to this rule is in Hawaii, where upslope flow due to the trade winds lead to one of the wettest locations on Earth. Otherwise, the flow of the Westerlies into the Rocky Mountains lead to the wettest, and at elevation snowiest, locations within North America. In Asia during the wet season, the flow of moist air into the Himalayas leads to some of the greatest rainfall amounts measured on Earth in northeast India.

Measurement
The standard way of measuring rainfall or snowfall is the standard rain gauge, which can be found in 100 mm plastic and 200 mm metal varieties. The inner cylinder is filled by 25 mm of rain, with overflow flowing into the outer cylinder. Plastic gauges have markings on the inner cylinder down to 0.25 mm resolution, while metal gauges require use of a stick designed with the appropriate 0.25 mm markings. After the inner cylinder is filled, the amount inside is discarded, then filled with the remaining rainfall in the outer cylinder until all the fluid in the outer cylinder is gone, adding to the overall total until the outer cylinder is empty. These gauges are used in the winter by removing the funnel and inner cylinder and allowing snow and freezing rain to collect inside the outer cylinder. Some add anti-freeze to their gauge so they do not have to melt the snow or ice that falls into the gauge. Once the snowfall/ice is finished accumulating, or as 300 mm is approached, one can either bring it inside to melt, or use lukewarm water to fill the inner cylinder with in order to melt the frozen precipitation in the outer cylinder, keeping track of the warm fluid added, which is subsequently subtracted from the overall total once all the ice/snow is melted.

Other types of gauges include the popular wedge gauge (the cheapest rain gauge and most fragile), the tipping bucket rain gauge, and the weighing rain gauge. The wedge and tipping bucket gauges have problems with snow. Attempts to compensate for snow/ice by warming the tipping bucket meet with limited success, since snow may sublimate if the gauge is kept much above freezing. Weighing gauges with antifreeze should do fine with snow, but again, the funnel needs to be removed before the event begins. For those looking to measure rainfall the most inexpensively, a can that is cylindrical with straight sides will act as a rain gauge if left out in the open, but its accuracy will depend on what ruler is used to measure the rain with. Any of the above rain gauges can be made at home, with enough know-how.

When a precipitation measurement is made, various networks exist across the United States and elsewhere where rainfall measurements can be submitted through the Internet, such as CoCoRAHS or GLOBE. If a network is not available in the area where one lives, the nearest local weather office will likely be interested in the measurement.

Hydrometeor definition
A concept used in precipitation measurement is the hydrometeor. Any particulates of liquid or solid water in the atmosphere are known as hydrometeors. Formations due to condensation, such as clouds, haze, fog, and mist, are composed of hydrometeors. All precipitation types are made up of hydrometeors by definition, including virga, which is precipitation which evaporates before reaching the ground. Particles blown from the Earth's surface by wind, such as blowing snow and blowing sea spray, are also hydrometeors, as are hail and snow.

Satellite estimates
Although surface precipitation gauges are considered the standard for measuring precipitation, there are many areas in which their use is not feasible. This includes the vast expanses of ocean and remote land areas. In other cases, social, technical or administrative issues prevent the dissemination of gauge observations. As a result, the modern global record of precipitation largely depends on satellite observations.

Satellite sensors work by remotely sensing precipitation—recording various parts of the electromagnetic spectrum that theory and practice show are related to the occurrence and intensity of precipitation. The sensors are almost exclusively passive, recording what they see, similar to a camera, in contrast to active sensors (radar, lidar) that send out a signal and detect its impact on the area being observed.

Satellite sensors now in practical use for precipitation fall into two categories. Thermal infrared (IR) sensors record a channel around 11 micron wavelength and primarily give information about cloud tops. Due to the typical structure of the atmosphere, cloud-top temperatures are approximately inversely related to cloud-top heights, meaning colder clouds almost always occur at higher altitudes. Further, cloud tops with a lot of small-scale variation are likely to be more vigorous than smooth-topped clouds. Various mathematical schemes, or algorithms, use these and other properties to estimate precipitation from the IR data.

The second category of sensor channels is in the microwave part of the electromagnetic spectrum. The frequencies in use range from about 10 gigahertz to a few hundred GHz. Channels up to about 37 GHz primarily provide information on the liquid hydrometeors (rain and drizzle) in the lower parts of clouds, with larger amounts of liquid emitting higher amounts of microwave radiant energy. Channels above 37 GHz display emission signals, but are dominated by the action of solid hydrometeors (snow, graupel, etc.) to scatter microwave radiant energy. Satellites such as the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission employ microwave sensors to form precipitation estimates.

Additional sensor channels and products have been demonstrated to provide additional useful information including visible channels, additional IR channels, water vapor channels and atmospheric sounding retrievals. However, most precipitation data sets in current use do not employ these data sources.

Satellite data sets
The IR estimates have rather low skill at short time and space scales, but are available very frequently (15 minutes or more often) from satellites in geosynchronous Earth orbit. IR works best in cases of deep, vigorous convection—such as the tropics—and becomes progressively less useful in areas where stratiform (layered) precipitation dominates, especially in mid- and high-latitude regions. The more-direct physical connection between hydrometeors and microwave channels gives the microwave estimates greater skill on short time and space scales than is true for IR. However, microwave sensors fly only on low Earth orbit satellites, and there are few enough of them that the average time between observations exceeds three hours. This several-hour interval is insufficient to adequately document precipitation because of the transient nature of most precipitation systems as well as the inability of a single satellite to appropriately capture the typical daily cycle of precipitation at a given location.

Since the late 1990s, several algorithms have been developed to combine precipitation data from multiple satellites' sensors, seeking to emphasize the strengths and minimize the weaknesses of the individual input data sets. The goal is to provide "best" estimates of precipitation on a uniform time/space grid, usually for as much of the globe as possible. In some cases the long-term homogeneity of the dataset is emphasized, which is the Climate Data Record standard.

In other cases, the goal is producing the best instantaneous satellite estimate, which is the High Resolution Precipitation Product approach. In either case, of course, the less-emphasized goal is also considered desirable. One key result of the multi-satellite studies is that including even a small amount of surface gauge data is very useful for controlling the biases that are endemic to satellite estimates. The difficulties in using gauge data are that 1) their availability is limited, as noted above, and 2) the best analyses of gauge data take two months or more after the observation time to undergo the necessary transmission, assembly, processing and quality control. Thus, precipitation estimates that include gauge data tend to be produced further after the observation time than the no-gauge estimates. As a result, while estimates that include gauge data may provide a more accurate depiction of the "true" precipitation, they are generally not suited for real- or near-real-time applications.

The work described has resulted in a variety of datasets possessing different formats, time/space grids, periods of record and regions of coverage, input datasets, and analysis procedures, as well as many different forms of dataset version designators. In many cases, one of the modern multi-satellite data sets is the best choice for general use.

Return period
The likelihood or probability of an event with a specified intensity and duration is called the return period or frequency. The intensity of a storm can be predicted for any return period and storm duration, from charts based on historical data for the location. The term 1 in 10 year storm describes a rainfall event which is rare and is only likely to occur once every 10 years, so it has a 10 percent likelihood any given year. The rainfall will be greater and the flooding will be worse than the worst storm expected in any single year. The term 1 in 100 year storm describes a rainfall event which is extremely rare and which will occur with a likelihood of only once in a century, so has a 1 percent likelihood in any given year. The rainfall will be extreme and flooding to be worse than a 1 in 10 year event. As with all probability events, it is possible though unlikely to have two "1 in 100 Year Storms" in a single year.

Uneven pattern of precipitation
A significant portion of the annual precipitation in any particular place (no weather station in Africa or South America were considered) falls on only a few days, typically about 50% during the 12 days with the most precipitation.

Role in Köppen climate classification
The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. Specifically, the primary types are A, tropical; B, dry; C, mild mid-latitude; D, cold mid-latitude; and E, polar. The five primary classifications can be further divided into secondary classifications such as rain forest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, steppe, subarctic climate, tundra, polar ice cap, and desert.

Rain forests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1750 and 2000 mm. A tropical savanna is a grassland biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes, with rainfall between 750 and 1270 mm a year. They are widespread on Africa, and are also found in India, the northern parts of South America, Malaysia, and Australia. The humid subtropical climate zone is where winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and from occasional tropical cyclones. Humid subtropical climates lie on the east side continents, roughly between latitudes 20° and 40° degrees from the equator.

An oceanic (or maritime) climate is typically found along the west coasts at the middle latitudes of all the world's continents, bordering cool oceans, as well as southeastern Australia, and is accompanied by plentiful precipitation year-round. The Mediterranean climate regime resembles the climate of the lands in the Mediterranean Basin, parts of western North America, parts of western and southern Australia, in southwestern South Africa and in parts of central Chile. The climate is characterized by hot, dry summers and cool, wet winters. A steppe is a dry grassland. Subarctic climates are cold with continuous permafrost and little precipitation.

Effect on agriculture
Precipitation, especially rain, has a dramatic effect on agriculture. All plants need at least some water to survive, therefore rain (being the most effective means of watering) is important to agriculture. While a regular rain pattern is usually vital to healthy plants, too much or too little rainfall can be harmful, even devastating to crops. Drought can kill crops and increase erosion, while overly wet weather can cause harmful fungus growth. Plants need varying amounts of rainfall to survive. For example, certain cacti require small amounts of water, while tropical plants may need up to hundreds of inches of rain per year to survive.

In areas with wet and dry seasons, soil nutrients diminish and erosion increases during the wet season. Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before the first harvest, which occurs late in the wet season.

Changes due to global warming
Increasing temperatures tend to increase evaporation which leads to more precipitation. Precipitation has generally increased over land north of 30°N from 1900 to 2005 but has declined over the tropics since the 1970s. Globally there has been no statistically significant overall trend in precipitation over the past century, although trends have varied widely by region and over time. In 2018, a study assessing changes in precipitation across spatial scales using a high-resolution global precipitation dataset of over 33+ years, concluded that "While there are regional trends, there is no evidence of increase in precipitation at the global scale in response to the observed global warming."

Each region of the world is going to have changes in precipitation due to their unique conditions. Eastern portions of North and South America, northern Europe, and northern and central Asia have become wetter. The Sahel, the Mediterranean, southern Africa and parts of southern Asia have become drier. There has been an increase in the number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughts—especially in the tropics and subtropics. Changes in precipitation and evaporation over the oceans are suggested by the decreased salinity of mid- and high-latitude waters (implying more precipitation), along with increased salinity in lower latitudes (implying less precipitation, more evaporation, or both). Over the contiguous United States, total annual precipitation increased at an average rate of 6.1% per century since 1900, with the greatest increases within the East North Central climate region (11.6% per century) and the South (11.1%). Hawaii was the only region to show a decrease (−9.25%).

Changes due to urban heat island
The urban heat island warms cities 0.6 to 5.6 C-change above surrounding suburbs and rural areas. This extra heat leads to greater upward motion, which can induce additional shower and thunderstorm activity. Rainfall rates downwind of cities are increased between 48% and 116%. Partly as a result of this warming, monthly rainfall is about 28% greater between 20 and 40 mi downwind of cities, compared with upwind. Some cities induce a total precipitation increase of 51%.

Forecasting
The Quantitative Precipitation Forecast (abbreviated QPF) is the expected amount of liquid precipitation accumulated over a specified time period over a specified area. A QPF will be specified when a measurable precipitation type reaching a minimum threshold is forecast for any hour during a QPF valid period. Precipitation forecasts tend to be bound by synoptic hours such as 0000, 0600, 1200 and 1800 GMT. Terrain is considered in QPFs by use of topography or based upon climatological precipitation patterns from observations with fine detail. Starting in the mid to late 1990s, QPFs were used within hydrologic forecast models to simulate impact to rivers throughout the United States. Forecast models show significant sensitivity to humidity levels within the planetary boundary layer, or in the lowest levels of the atmosphere, which decreases with height. QPF can be generated on a quantitative, forecasting amounts, or a qualitative, forecasting the probability of a specific amount, basis. Radar imagery forecasting techniques show higher skill than model forecasts within six to seven hours of the time of the radar image. The forecasts can be verified through use of rain gauge measurements, weather radar estimates, or a combination of both. Various skill scores can be determined to measure the value of the rainfall forecast.

title: Precipitation


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Precipitation (chemistry)

In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant.

The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the supernate or supernatant.

The notion of precipitation can also be extended to other domains of chemistry (organic chemistry and biochemistry) and even be applied to the solid phases (e.g. metallurgy and alloys) when solid impurities segregate from a solid phase.

Supersaturation
The precipitation of a compound may occur when its concentration exceeds its solubility. This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution.

The formation of a precipitate can be caused by a chemical reaction. When a barium chloride solution reacts with sulphuric acid, a white precipitate of barium sulfate is formed. When a potassium iodide solution reacts with a lead(II) nitrate solution, a yellow precipitate of lead(II) iodide is formed.

Inorganic chemistry
Precipitate formation is useful in the detection of the type of cation in a salt. To do this, an alkali first reacts with the unknown salt to produce a precipitate that is the hydroxide of the unknown salt. To identify the cation, the color of the precipitate and its solubility in excess are noted. Similar processes are often used in sequence – for example, a barium nitrate solution will react with sulfate ions to form a solid barium sulfate precipitate, indicating that it is likely that sulfate ions are present.

A common example of precipitation from aqueous solution is that of silver chloride. When silver nitrate (AgNO3) is added to a solution of potassium chloride (KCl) the precipitation of a white solid (AgCl) is observed.

The ionic equation allows to write this reaction by detailing the dissociated ions present in aqueous solution.

Reductive precipitation
The Walden reductor is an illustration of a reduction reaction directly accompanied by the precipitation of a less soluble compound because of its lower chemical valence:

The Walden reductor made of tiny silver crystals obtained by the immersion of a copper wire into a solution of silver nitrate is used to reduce to their lower valence any metallic ion located above the silver couple (Ag+ + 1 e– → Ag) in the redox potential scale.

Colloidal suspensions
Without sufficient attraction forces (e.g., Van der Waals force) to aggregate the solid particles together and to remove them from solution by gravity (settling), they remain in suspension and form colloids. Sedimentation can be accelerated by high speed centrifugation. The compact mass thus obtained is sometimes referred to as a 'pellet'.

Digestion and precipitates ageing
Digestion, or precipitate ageing, happens when a freshly formed precipitate is left, usually at a higher temperature, in the solution from which it precipitates. It results in purer and larger recrystallized particles. The physico-chemical process underlying digestion is called Ostwald ripening.

Organic chemistry
While precipitation reactions can be used for making pigments, removing ions from solution in water treatment, and in classical qualitative inorganic analysis, precipitation is also commonly used to isolate the products of an organic reaction during workup and purification operations. Ideally, the product of the reaction is insoluble in the solvent used for the reaction. Thus, it precipitates as it is formed, preferably forming pure crystals. An example of this would be the synthesis of porphyrins in refluxing propionic acid. By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration on a Büchner filter as illustrated by the photograph here beside:

Precipitation may also occur when an antisolvent (a solvent in which the product is insoluble) is added, drastically reducing the solubility of the desired product. Thereafter, the precipitate may be easily separated by decanting, filtration, or by centrifugation. An example would be the synthesis of Cr3+tetraphenylporphyrin chloride: water is added to the dimethylformamide (DMF) solution in which the reaction occurred, and the product precipitates. Precipitation is useful in purifying many other products: e.g., crude bmim-Cl is taken up in acetonitrile, and dropped into ethyl acetate, where it precipitates.

Biochemistry
Proteins purification and separation can be performed by precipitation in changing the nature of the solvent or the value of its relative permittivity (e.g., by replacing water by ethanol), or by increasing the ionic strength of the solution. As proteins have complex tertiary and quaternary structures due to their specific folding and various weak intermolecular interactions (e.g., hydrogen bridges), these superstructures can be modified and proteins denaturated and precipitated. Another important application of an antisolvent is in ethanol precipitation of DNA.

Metallurgy and alloys
In solid phases, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to e.g. rapid quenching or ion implantation, and the temperature is high enough that diffusion can lead to segregation into precipitates. Precipitation in solids is routinely used to synthesize nanoclusters.

In metallurgy, precipitation from a solid solution is also a way to strengthen alloys.

Precipitation of ceramic phases in metallic alloys such as zirconium hydrides in zircaloy cladding of nuclear fuel pins can also render metallic alloys brittle and lead to their mechanical failure. Correctly mastering the precise temperature and pressure conditions when cooling down spent nuclear fuels is therefore essential to avoid damaging their cladding and to preserve the integrity of the spent fuel elements on the long term in dry storage casks and in geological disposal conditions.

Industrial processes
Hydroxide precipitation is probably the most widely used industrial precipitation process in which metal hydroxides are formed by adding calcium hydroxide (slaked lime) or sodium hydroxide (caustic soda) as precipitant.

History
Powders derived from different precipitation processes have also historically been known as 'flowers'.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Precipitation (chemistry)


text:
SJ AB

SJ (formally SJ AB) is a state-owned passenger train operator in Sweden. SJ was created in 2001, out of the public transport division of Statens Järnvägar, when the former government agency was divided into six separate state-owned limited companies. In 2018, SJ carried 31.8 million passengers.

Overview
SJ's operations fall broadly into subsidised and unsubsidised services. The unsubsidised services ran until the 2011 monopoly. The subsidised trains are awarded through competitive bids. However, some trains fall in between these categories, since public transit agencies can pay SJ to allow transit pass holders access to SJ's trains.

SJ received a government bailout a few years after its creation, but has since had profit margins of up to ten percent. All train operators in Sweden pay low track access charges to the track authority, Trafikverket.

SJ higher speed services (SJ Snabbtåg)
X2 serves for higher speed trains, with a top speed of 200 km/h, and tilts during high speed turns. The trains currently serves Stockholm-Gothenburg (Västra Stambanan) and Stockholm-Malmö-Copenhagen (Södra Stambanan and Öresund Line), but have previously served the lines Stockholm-Sundsvall and, seasonally, Stockholm-Strömstad, Stockholm-Oslo and Stockholm-Östersund-(Duved) lines. There are about 40 X2 sets in service.

X55 is a newer train introduced in 2012. The interior is mainly modern style, and the train has a top speed of 200 km/h and serves Stockholm-Östersund-(Duved) (Mittbanan-Norra Stambanan)-Stockholm-Uddevalla (Västra Stambanan and Bohusbanan) to advance to Gothenburg for night parking-Stockholm-Sundsvall-Umeå (Ostkustbanan, Botniabanan), Gothenburg-Malmö (Västkustbanan), Stockholm-Oslo or Stockholm-Karlstad (Västra Stambanan and Värmlandsbanan/Kongsvingerbanen) and Stockholm-Falun/Mora (Dalabanan). Some of these lines are run under the SJ InterCity-brand despite no difference in product with other lines run by the X55 train. SJ has ordered 25 Bombardier Zefiro high speed trains for 250 km/h to be delivered in 2026.

SJ InterCity
InterCity trains are Rc-hauled trains, often with many 2nd class cars, X55 trains or X40 trains. InterCity trains also have a bistro car, with the exception of the X40 that has no form of catering.

SJ Regional
SJ Regional services include double-deckers (X40), pull trains, X50 and X52 cars. The trains do not serve meals or drinks. The trains do not usually travel distances over 4 hours, except Coast to Coast (Gothenburg-Kalmar) and Stockholm-Gothenburg via Västerås. Most trains have first class, except the X50 and X52 trains. All push and pull regional services have since 2020 been replaced with new ER1 trains. A normal order in a pull train was AB7-BF7-B7 or B7-BF7-B7 or AB7-B7-BF7-B7. These trains were not usually longer than 4 cars, except Uppsalapendeln (Stockholm-Uppsala) which often has 8 cars and is a push and pull.

Sleeper services - SJ Nattåg
The SJ overnight train services (Swedish: SJ Nattåg) are Rc locomotive-hauled trains with both sleeper wagons as well as standard wagons. All services except for the Stockholm-Malmö route have a bistro wagon.

As of 2022 SJ has in collaboration with DSB and RDC begun to operate night train services between Sweden and Germany through Denmark. Three different locomotives are used due to compatibility issues with the electrification and signaling systems between the three countries.

Within Sweden are SJ Rc locomotives used, and in Denmark are DSB EA used, and in Germany are DB 101 used.

The night-trains are operated on the following lines:

SJ InterCity
The InterCity services are Rc-hauled trains with standard-seating carriages in both first and second class. There is always a bistro car available in the trainset.

Lines with InterCity service:

SJ Regional
Most of the SJ Regional network was concentrated in the area around lake Mälaren. Operated with either Rc-hauled trainsets, X12/X14 or X40 EMUs. These trains have no catering on board. The X40 is equipped with free 4G WiFi. Both first and second-class are usually offered. Most of this network has been incorporated into the new Mälartåg franchise, although some services remain outside of it.

Routes listed below are the satellite routes which are not subject to franchising.

Franchised operations
SJ operate a couple of regional rail franchises held by public transport authorities around the country. The most significant of these are Mälartåg and Västtågen serving the Mälaren valley and the region of West Götaland respectively. SJ AB also started operating the Öresundståg franchise for the 2020 timetable, taking over from Transdev. But due to serious inconsistencies between partners the contract will be terminated as of December 2022 where Transdev will take over again . MTR took over the Mälartåg contract in December 2021.

The stretch Malmö Central to Copenhagen Central is operated 50/50 alongside Danish State Railways (DSB) and Copenhagen to Østerport/Nivå by DSB only.

The initial contract for the Mälartåg franchise states that the operator may use their own fleet [of X12, X40 and X50 stock] until the delivery of ER1 Stadler Dosto 200 EMUs is completed. The Upptåget franchise will be merged into Mälartåg onwards from the 2022 timetable, meaning that services from Gävle gain additional stations inherited from the termination of the Upptåget franchise.

SJ higher speed trains
SJ higher speed trains (Swedish: SJ Snabbtåg) are X2 or X55 trains operating on the main routes in Sweden. The trains are equipped with WiFi and have a bistro. Stops at Arlanda and Uppsala are for boarding northbound or alighting southbound respectively, although passengers with railcards are exempted from this rule. Some services do also allow both boarding and alighting at Arlanda and Uppsala respectively.

SJ Norge
On 7 June 2020 SJ Norge commenced operating services on the Trøndelag Commuter Rail, as well as the Meråker, Røros, Rauma, Nordland, the Saltpendel Line and the Dovre Regional Line under a 10-year contract with the Norwegian Railway Directorate.

SJ is also set to start up services on the Stockholm - Trondheim stretch as soon as the Norwegian part of the railway is electrified. SJ will operate trains owned by Norske Tog (Norwegian Trains) and these are:

 * Class 76 or Stadler FLIRT Bio-Modes (hybrid electric EMUs) as well as Di - 4 diesel-electric locomotives and Class 92 Duewag DMUs
 * EL18 electric locomotives, Class 93 Bombardier Talent DMUs, and Class 73 ADtranz EMUs.

The rail routes SJ Norge operate are:

 * Steinkjer – Trondheim Central
 * Steinkjer – Lerkendal/Trondheim Outskirts
 * Steinkjer – Lundamo
 * Steinkjer – Melhus
 * Lerkendal/Trondheim Outskirts – Trondheim Central
 * Trondheim Central – Heimdal
 * Trondheim Central – Melhus
 * Trondheim Central – Lundamo
 * Trondheim Central – Røros
 * Trondheim Central – Stjørdal/Værnes Airport
 * Heimdal – Storlien (interchange with Norrtåg toward Östersund
 * Trondheim Central – Bodø
 * Trondheim Central – Mo i Rana
 * Trondheim Central – Oslo Central
 * Rotvoll – Røros
 * Rotvoll – Støren
 * Steinkjer – Støren
 * Røros – Hamar
 * Saltenpendelen

The rail routes SJ Norge are set to operate are:

 * Stockholm — Trondheim

Identity document requirements
From September 2009, SJ requires an identity document from passengers with a pre-paid ticket (which is mandatory on many trains). This can be a Nordic ID card or any passport. This is due to an effort to stop private trading of train tickets.

title: SJ AB


text:
Talk:Messerschmitt Me 262

Meteor
User:BilCat reverted me saying "it's the second jet fighter, and first allied one, so naturally itll.be compared"

I think that's a pretty weak argument for reverting my change that was well explained without going to the talk page or contacting me. There are several problems with that. One is the fact it was second is irrelevant, another is most readers of that page will have never even heard of the Gloster even if they are relatively well versed in the air war over Europe because it makes no contribution at all. There's no combat footage and no combat stories. Another is that it looks like it was tagged on to the sentence that was trying to make the point that the 262 was faster and outgunned the fighters that it actually faced in combat which doesn't include the Gloster.

"The Me 262 was faster and more heavily armed than any Allied fighter, including the British jet-powered Gloster Meteor."

Does a "fighter" that doesn't fight deserve to be mentioned in the same breath as the legendary Me 262? The Gloster Meteor was a fighter in name only. It was not used in air to air combat at all. It has no air-to-air combat kills. It saw no combat over Europe and would never have seen a ME262. In fact, flying the aircraft over the continent was forbidden because they didn't want one falling into German hands. It no more deserves mention than the Bell P-59 Airacomet or the Lockheed P-80 Shooting Star which were both operational and deployed but never saw combat. When I read the article and saw it mentioned I thought "Gloster,? what's that doing here?" so I ended up in the British national archives looking at Gloster squadron daily reports. I was not used as a combat aircraft. The same can be said for the P-59 and P-80. It's an interesting side note that they destroyed maybe a dozen buzz bombs include some where the pilot used his wingtip vortices to upset the airflow over the wingtip of the bomb and spun them out of control. But that is not air-to-air combat. They trained for combat but didn't do any, not even over England. I find no evidence they shot down a single piloted aircraft. What is the argument for including it? The point being made on the page was that the 262 was faster and more heavily armed than any allied fight that it faced in combat. That did not include the Gloster. Jackhammer111 (talk) 22:13, 6 September 2021 (UTC)

 * I think you're reading far too much into what is just a general statement in the lead section, which is about Allied fighters in general, not just those it faced in combat. If you want to change the statement to say that, then propose doing that, along with reliable sources. You seem to have some objection to even mentioning the Meteor, or "Gloster" as you call it. The Meteor, unlike the Me 262, went on to have a long and relatively successful career with the RAF, and was also exported to several countries. So the fact that it was the first Allied jet fighter of the war is important to note, whether or not it ever faced the Me 262 in combat. BilCat (talk) 22:24, 6 September 2021 (UTC)
 * The Meteor was operational in Belgium. 88.98.205.213 (talk) 22:55, 28 October 2023 (UTC)
 * The Meteor was in Belgium and Holland, hoping the 262s would attack them. They destroyed 46 planes on the ground.
 * The Meteor was too advanced to allow the Germans to get hold of a crashed plane on their territory. 88.98.205.213 (talk) 23:04, 28 October 2023 (UTC)

 * It is not important to note here. You're not reading enough into it. The page and its lead are NOT about Allied fighters in general, it is about the ME262 in particular. I'm pointing out the glaring lack of relevance. It is no more relevant as a combat fighter than the P-59 and P-80. I'd be making the same argument if someone had tagged them onto that sentence. I don't object to mention of the Meteor, I object to it being mention here. This is not a page about the Meteor. It is notable as the first but f you want to note it put it on the Gloster Meteor page or put it somewhere other than the lead on the 262 pages. "The Meteor, unlike the Me 262, went on to have a long and relatively successful career". Unlike the Me 262? Seriously? That is an absurd thing to say. It did not have a long career as an air-to-air combat fighter but even if it did that doesn't make it relevant here. It is not a comparable aircraft. No combat in WWII and here is the first encounter of Meteors with Mig 15s in Korea. " 1 December (1951 )when twelve Meteors were engaged by over fifty MiG 15s over Pyongyang. For the destruction of one MiG, the squadron lost three Meteors with a further two damaged. This encounter highlighted the MiG's superiority in aerial combat, and as a result, the Meteors were confined to ground attack operations." In WWII it was not a fighter. That's what is relevant here.

https://www.airforce.gov.au/sites/default/files/minisite/static/7522/RAAFmuseum/research/units/77sqn.htm

Jackhammer111 (talk) 19:51, 8 September 2021 (UTC)

 * The article mentions the Meteor several times in its main text, this is because reliable sources on the Me 262 also tend to mention the Meteor. The lead of the article is a summary of the main body, so it naturally briefly mentions the Meteor. This is how Wikipedia works - it reflects what is in reliable sources. (Hohum @ ) 02:54, 10 September 2021 (UTC)

 * No, it does not get mentioned several times in the text. It gets mentioned twice in the body and I can understand the relevance there especially in the second mention in the body about post-war testing which goes on to mention the Lockheed shooting star. That is different than putting it in the lead. Obviously, everything that's mentioned in the article doesn't get mentioned in the lead anyway So there's nothing natural about it. I have been editing for 15 years so I don't need to be told how Wikipedia works. The obvious and Central point being made in the lead is that it was faster and more well-armed than any of the planes that it flew against in combat and was a dangerous aircraft that could have had serious consequences had it been developed earlier in the war. The Gloster jet was not an aircraft of consequence. It's like a false equivalency to be mentioning it in the same sentence in the lead as the 262. It did not fly against the Gloster meteor in combat, it flew against propeller-driven aircraft. The planes never met each other in the air so tell me again why it should be in the lead. Nobody yet has made that argument. The citation that comes after that line is to a book that's merely a directory of aircraft. So using that as a source you could also include two United States jet fighters that never saw air-to-air combat. Certainly, you wouldn't want me to do that to the lead just to prove a point. In fact, that would be so absurd that it makes my point for me. The Source in the lead merely proves that the aircraft existed. I'm still waiting you're somebody to argue why it belongs there. It did not shoot down a single German-manned aircraft. Jackhammer111 (talk) 21:39, 18 September 2021 (UTC)
 * It has has been pointed out why, multiple times, by different people. (Hohum @ ) 02:20, 19 September 2021 (UTC)
 * You Jackhammer111 (talk) 19:23, 17 March 2022 (UTC)

The Meteor is naturally mentioned as a comparator because it was the only other jet fighter to see operational service during the war, and indeed entered regular squadron service in late July 1944, shooting down enemy cruise missiles that August, while the 262 did not reach regular operational status until 1945 (serving only with a trials unit in 1944, and notably failing in its primary assigned task, to shoot down an RAF reconnaissance Mosquito). The Meteor and the 262 never met in combat for several reasons: only one squadron of Meteors was deployed to the Continent, they were forbidden to fly over enemy territory for the first few weeks and Me262s were by then tasked almost exclusively to intercept American day-bomber formations, which Meteors did not escort. By that time, Allied fighters not engaged in bomber escort seldom encountered German fighters. It did happen on the odd occasion, and RAF Tempests and Spitfire XIVs did destroy German jets, but it never happened to the Meteors, which like the Tempests and Spit XIVs were assigned to 'armed reconnaissance' at low level and mostly involved in ground attack. Ground attack was the principal task of Allied fighters at the time, since the Luftwaffe was a shrivelled husk and did not do very much except harass American bomber formations to remarkably little effect. The Meteor is not comparable to the P-59 or P-80 since neither of those machines saw service in the theatre of operations during the war. The Meteor and the 262 were the only jet fighters to achieve this, the Me163 being a rocket and the Ar234 being a bomber and reconnaissance aircraft. Khamba Tendal (talk) 19:27, 20 November 2022 (UTC)

 * Operational is when the plane has a trained ground and flight crews, with spare parts and ready to be deployed anywhere. The 262 was with a testing unit until Nov 1944. The first operational jet plane was the Meteor by a number of months.
 * The 262 did not shoot down a Meteor in July 1944. The Meteor landed in Italy. A fuselage door was blown off in a quick evasive action that was all.
 * The Meteor at the war's end was faster than the 262 with improved engines.
 * The Meteor was flying operationally until the 1980s/ Still flying today by Martin Baker.
 * After WW2 no one took up the 262s design which was based on a 1938 propeller air-frame.
 * The Meteor was an all new air-frame for jet engines - forward pilot position, high tail so as not to obstruct jet thrust flow, tricycle landing gear, etc.
 * This article is full of overt errors, written by fanboys.
 * 88.98.205.213 (talk) 22:51, 28 October 2023 (UTC)
 * If you have WP:Reliable sources to back all that up, then you can fix it. (Hohum @ ) 22:56, 28 October 2023 (UTC)
 * Well, the article's claim, under 'Introduction', that the 262 'could accelerate to speeds over 530mph, about 93mph faster than any Allied fighter in the European Theater of Operations' is cited to an American source and only in fact applies to US fighters, specifically the P-51 at 437mph (the British Spitfire XIV being about 10mph faster), while the Meteor F.3 operational with 616 Squadron RAF on the Continent from March 1945 was tested to 493mph at 30,000ft (William Green, War Planes of the Second World War: Fighters, Vol.II, Macdonald, London, 1961, ISBN 356 01446 0, p.56). This is fairly academic, since the Meteor and the 262 never met in combat, but still. The Meteor went on to set two world speed records of 606mph and 616 mph just after the war, while flight test (and bitter German experience) had established that any 262 attempting to go anywhere near that sort of speed would suffer a fatal rearward shift of the centre of pressure, putting the aircraft into an irrecoverable nose-dive, which is why so many 262 pilots died in crashes. The 262's airframe had severe high-Mach problems and its critical limit appears to have been inferior to the Spitfire's. (Spitfire PR XI PL827 was regularly and safely dived to Mach 0.85. PR XI EN409 achieved Mach 0.92. As the article notes, Messerschmitt was aware that the 262 could not reach Mach 0.86 and survive, and nor could its pilot.)
 * Additionally, the article's claim, in the lede, that the 262 influenced the design of the F-86, the MiG-15 and the B-47 is again odd, since a mere glance at the respective aircraft shows that they were swept-wing, which the 262 was not (its mild degree of sweep, done purely for centre-of-gravity reasons, does not amount to a swept-wing design). And the Soviet jet had a British-designed centrifugal engine (the Rolls-Royce Nene, reverse-engineered by the Russians), while the axial engines of the US types derived from the British Metrovick engine and not the German pattern.
 * The article isn't altogether bad, but it does suffer from the problem that the 262, because of its stylish appearance and its association with the Third Reich, has become a cult object which attracts fanboi claims. Khamba Tendal (talk) 19:12, 20 November 2023 (UTC)

Reference to "nose wheel" is nonsensical
This passage under "Test flights":

Its only major deficiency was that brakes could not be used until the nose wheel had touched down, because engaging them before would smash the nose wheel strongly into the runway, potentially destroying the nose wheel and even the aircraft.

Elsewhere (and just looking at the photos) the aircraft is described as using conventional landing gear, which does not have a nose wheel (such aircraft have, as pictured, a TAIL wheel). It sounds like applying the breaks too early could lead to the nose of the plane crashing into the runway, but no nosewheel would be involved in such a situation, as no nose wheel exists. I think this paragraph needs to be completely rewritten, but I'm not an authority on this. Kswoll (talk) 13:15, 27 November 2023 (UTC)

 * The first few prototypes had conventional (tailwheel) landing gear, later revised to tricycle gear for production aircraft. The first paragraph in the 'test flights' section is at minimum therefore misplaced, in that it seems not to be referring to test flights at all. The reference to smashing the nosewheel clearly applies to later aircraft, is out of chronological sequence, and probably belongs at the end of the section, or elsewhere. And given that the paragraph is based solely on a single primary source - the debriefing of Luftwaffe test pilot Hans Fey - we should probably make it clearer that it is all his subjective opinion, rather than an authoritative independent assessment. AndyTheGrump (talk) 13:38, 27 November 2023 (UTC)

 * Looking into this further, I've removed the paragraph detailing Englander's debriefing of Fay entirely, for now at least. Not only was the paragraph out of place chronologically, but the way it was worded was misleading - describing it as "a report by Major Ernst Englander", rather than what is actually was: a debriefing of a Messerschmitt test pilot, Hans Fay. The comments on the attributes of the Me 262 are Fay's, not Englander's. And even if we take the source as legitimate (which it most likely is, though I'd rather see an alternative source for what is clearly a transcription - preferably one that actually stated where the original could be located) it is very much primary, and originates in circumstances where objectivity might very well be called into question. As I understand it, the general practice amongst the allies when interviewing POWs was to record what they said more or less verbatim, rather than immediately analyse it for veracity - intelligence was collated later, through cross-checking of sources. Accordingly, I don't think we should be using this debriefing in the manner it has been in this article - as an objective report on the handling of the Me 262. Such commentary is better left to secondary sources, and if we decide to include Fay's opinions at all, make the circumstances under which he expressed them clearer. AndyTheGrump (talk) 22:01, 30 November 2023 (UTC)

Projekt 1065 Gratz
Why does the link in the origins section link to a YA author? 2600:1702:4B05:800:5575:827B:FABB:50EC (talk) 02:42, 5 January 2024 (UTC)

 * Have removed it as an unlikely confusion. Nimbus (Cumulus nimbus floats by)  11:26, 18 January 2024 (UTC)

title: Talk:Messerschmitt Me 262