Hugo Laffolley
email: hugo.laffolley@cea.fr

Christophe Journeau

Jules Delacroix

Bernd Grambow

Christophe Suteau

Synthesis of Fukushima Daiichi Cs-bearing microparticles through molten core-concrete interaction in nitrogen atmosphere

Keywords: CsMP, Fukushima Daiichi, experimental synthesis, molten core-concrete interaction

teaching and research institutions in France or abroad, or from public or private research centers.

MAIN BODY

In 2011, three reactors of the Fukushima Daiichi Nuclear Power Station (FDNPS) experienced core meltdown due to a loss of coolant in the primary loop. The total source term (excluding noble gases) is estimated to be of 520 PBq [START_REF] Steinhauser | Comparison of the Chernobyl and Fukushima nuclear accidents: A review of the environmental impacts[END_REF]. Radionuclides were released into the Pacific Ocean and on Japanese lands, depending on the wind direction [START_REF] Katata | Atmospheric discharge and dispersion of radionuclides during the Fukushima Dai-ichi Nuclear Power Plant accident. Part I: Source term estimation and local-scale atmospheric dispersion in early phase of the accident[END_REF].

On March 14 th and 15 th , radioactive Cs-bearing Microparticles (CsMP) were discovered on air monitoring filters at Tsukuba, Japan (170 km southwest of the FDNPS) [START_REF] Adachi | Emission of spherical cesium-bearing particles from an early stage of the Fukushima nuclear accident[END_REF] (Figure 1). CsMP are micrometric particles mainly made of amorphous silica, containing a diversity of other major elements (depending on the particle analysed) such as iron (Fe), zinc (Zn), tin (Sn), potassium (K), rubidium (Rb), chlorine (Cl), carbon (C), sodium (Na) and caesium (Cs) [START_REF] Kogure | Constituent elements and their distribution in the radioactive Cs-bearing silicate glass microparticles released from Fukushima nuclear plant[END_REF][START_REF] Yamaguchi | Internal structure of cesium-bearing radioactive microparticles released from Fukushima nuclear power plant[END_REF]. Cs is the principal source of radioactivity of CsMP due to its radioisotopes 134 Cs and 137 Cs (half-lives of 2.2 and 30 years respectively [START_REF] Finston | The radiochemistry of cesium[END_REF]). Other elements such as actinides or fission products (FP) can also be found as traces or inclusions [START_REF] Hagiwara | Characterization of radiocesium-bearing microparticles with different morphologies in soil around the Fukushima Daiichi nuclear power plant[END_REF][START_REF] Kurihara | Particulate plutonium released from the Fukushima Daiichi meltdowns[END_REF]. It must be noted that this type of Cs-bearing particles had not been anticipated and is not currently taken into account in severe accident modelling. This paper reports the first achievement in the attempt of synthesising CsMP through molten core concrete interaction (MCCI), to provide key information about the FDNPS accident and improve the understanding of radioactive aerosol release after lower head failure and core relocation.

Experimental synthesis of type-A (i.e. ≈1 µm diameter and high specific radioactivity) CsMP has been set up on the VITI facility of PLINIUS platform to investigate the generation process and the physicochemical conditions of the source reactor [START_REF] Journeau | Upgrading the PLINIUS platform toward smarter prototypiccorium experimental R&D[END_REF]. Among the few hypotheses justifying a sufficient source of Si, molten core-concrete interaction (MCCI) after molten fuel relocation on the concrete pedestal is supported by several researchers and investigated in this study [START_REF] Furuki | Caesiumrich micro-particles: A window into the meltdown events at the Fukushima Daiichi Nuclear Power Plant[END_REF][START_REF] Ohnuki | Formation of radioactive cesium microparticles originating from the Fukushima Daiichi Nuclear Power Plant accident: characteristics and perspectives[END_REF]. Structural stainless steel, silicate insulation materials or high-efficiency particulate air filters are also considered as possible source of Si in the literature [START_REF] Zheng | A proposed formation mechanism of the Type-A radiocaesium-bearing microparticles released from Units 2/3 during the Fukushima Daiichi Nuclear Power Plant accident[END_REF][START_REF] Rizaal | Investigation of high-temperature chemical interaction of calcium silicate insulation and cesium hydroxide[END_REF][START_REF] Hidaka | Identification of Carbon in Glassy Cesium-Bearing Microparticles Using Electron Microscopy and Formation Mechanisms of the Microparticles[END_REF]. The basaltic concrete used for FDNPS construction contains around 60% wt. of SiO 2 [START_REF] Bouyer | Large scale Vulcano molten core-concrete interaction test considering Fukushima Daiichi condition[END_REF]. When the molten fuel, containing a significant fraction of sub-oxidised Zircaloy cladding, hits the pedestal, highly exothermic reactions take place, producing atomic Si or gaseous SiO, as the temperature increases [START_REF] Alsmeyer | Molten corium/concrete interaction and corium coolability: a state of the art report[END_REF]. Then, silicon-containing vapours spread in the Primary Containment Vessel (PCV) and may condense as SiO 2 in colder locations.

The experimental test section is composed of a zirconia crucible, containing a corium simulant and concrete in a closed zirconia chamber (Figure 2). The heating process is achieved by electromagnetic induction from a 4-turn cooled inductor, on a tungsten hollow cylinder, radiating on the chamber. The test section lies inside a 70L water-cooled stainless steel vessel filled with nitrogen at atmospheric pressure. The experimental set-up is also composed of a heated sample line (150 • C) to carry (and dilute) the aerosols from the vessel to a High-Efficiency Particulate Air (HEPA) filter and a particle counter (Pegasor®PPS-M).

An in-vessel corium composition has been defined to interact with concrete and simulate MCCI. For this set of trials, the corium composition is based on results of the OECD/NEA Benchmark Study of the Accident at the Fukushima Daiichi nuclear power plant (BSAF) project (Phase I, Unit 2) [START_REF] Pellegrini | Benchmark Study of the Accident at the Fukushima Daiichi NPS: Best-Estimate Case Comparison[END_REF]. The corium is composed of depleted uranium oxide, Zircaloy-2, zirconia, stainless steel, stainless steel oxides, boron carbide and some fission products of interest available as stable isotopes (Table S1). The concrete used for the trials is basaltic concrete based on the real composition of FDNPS concrete.

Aerosols are not collected all along the heating process but only at a defined target temperature. This experimental procedure has been designed to keep the most volatile species inside VITI vessel until the end of the trial. The target temperature is defined as the temperature providing a vapour composition that best satisfies the desired aerosol composition (i.e. CsMP composition). This temperature has been estimated by thermodynamics calculations using the Thermodynamics of Advanced Fuels -International Database (TAF-ID) and ThermoCalc software, considering that the gaseous phase may be an indicator of the final composition of particles [START_REF] Laffolley | Thermodynamics of aerosols during a molten core-concrete interaction at Fukushima Daiichi Unit 2 conditions[END_REF]. The collecting process starts as the crucible reaches 2200 • C (corium temperature between 2100 and 2200 • C) and lasts 10 to 30 seconds depending on the particle counting. Vessel pressure is slightly above the atmospheric pressure, ensuring the path of aerosols from the vessel to the sampling line. A moderate gas flow (5 L/min) blowing under the crucible (from the bottom to top direction) carries aerosols and prevents the pressure from dropping under 1 atm. A volumetric pump downstream ensures also that the gas flows through the HEPA filter.

The preparation process for Scanning Electron Microscopy (SEM) observations and Energy-Dispersive X-ray spectroscopy (EDX) analyses consists of taking a small HEPA filter portion (< 1 cm 2 ) with aerosols and transfer it into a test tube filled with a few millilitres of demineralised water. An energetic shaking of the tube (1 to 2 min) is performed to take off the aerosol from the filter, disperse them and dissolve soluble aerosols. The suspension is finally passed through a filter syringe (0.22 µm pores) to keep the insoluble aerosols. The filter is then dried at room temperature and fixed with carbon tape onto a sample holder. Samples are coated with carbon through vapour deposition for electric conduction.

Macroscopic SEM observations show a large diversity of aerosols with irregular shapes and sizes on the filter. Close observations led to the identification of numerous spherical particles with a diameter varying between 250 nm and 6.4 µm (Figure 3). The median diameter is around 2 µm, which is consistent with most of identified CsMP from the FDNPS [START_REF] Igarashi | A review of Csbearing microparticles in the environment emitted by the Fukushima Dai-ichi Nuclear Power Plant accident[END_REF]. In total, 21 spherical particles have been studied, all having a spherical shape and some small background aerosols sometimes stuck on the surface. In comparison, a particle has been identified on a non-dispersed sample (directly transferred onto the carbon tape) and seems to have more aerosol stuck on its surface, implying that the water dispersion mostly removed or dissolved the background aerosols on other particles. A study suggests that particles greater than 1 µm were mostly found because their radioactivity i.e. their radiocaesium content was higher, but even more minute particles exist. In this study, particles are only sought visually, with the microscope, implying that this bias is less likely to occur, although larger particles are easier to find [START_REF] Okumura | Finding Radiocesium-bearing Microparticles More Minute than Previously Reported, Emitted by the Fukushima Nuclear Accident[END_REF]. Moreover, if some synthesised particles have a diameter below 200 nm, they may have passed through the filter during the preparation process. These particles would require ultrafiltration to be isolated, after a segregation from background aerosols.

EDX chemical composition has for now been conducted on a few particles. This experimental method provides qualitative or semi-quantitative results on major elements. Light elements such as boron (B) cannot be accurately identified. Carbon contents cannot be assessed as the sample is coated with carbon. Chemical analyses have been made on specific particles, chosen for their size or background, as larger particles will provide spectra with less background noise. Particle 59 (diameter of 1.5 µm, very low background noise) is mainly made of Si and O, the other main elements are alkali elements (Na, K and Cs), Fe and magnesium (Mg) (Figure 4a). This EDX analysis suggest that the particle is mainly made of SiO 2 like CsMP. Na and K are reliable elements for further comparisons with CsMP since they are inherent concrete components, but Cs has been artificially added to the concrete composition and the Cs content of the particles may directly be influenced by the initial corium content in Cs. The Fe content of the particles is mainly due to the presence of stainless steel, even if concrete aggregates are a minor source of Fe. The largest particle collected (Figure 3, bottom right, diameter of 6.4 µm) has the same spectrum with slightly different intensities.

Other spectra with possible background influence show also contents of Ca, Zn, Al, S, and W, the latter due to pollution from the susceptor (Figure 4b). Ca, Al and S are major or minor elements of concrete and have been found in several CsMP. The source (thus initial quantity) of Zn is uncertain but supposed to be from paint. It was added in the experimental composition as ZnO (Table S1).

Semi-quantitative chemical analyses have been carried out and are compared with CsMP from other studies [START_REF] Okumura | Reactor environment during the Fukushima nuclear accident inferred from radiocaesium-bearing microparticles[END_REF][START_REF] Hagiwara | Characterization of radiocesium-bearing microparticles with different morphologies in soil around the Fukushima Daiichi nuclear power plant[END_REF]. Note the impossibility to determine carbon concentration even though carbon has been measured, sometimes more than Si in some particles of the literature [START_REF] Hagiwara | Characterization of radiocesium-bearing microparticles with different morphologies in soil around the Fukushima Daiichi nuclear power plant[END_REF]. Hence, the present semi-quantitative ratios on Si may be significantly underestimated. Al, Na and K are elements that are only provided by concrete in the experiments. Al is not found in every CsMP and often as a minor element (< 1% wt.), which is consistent with the three experimental particles considered here, as Al/Si ratios are in the same order of magnitude. K is found in every CsMP but seems to be in lower concentration compared to the synthesised particles with the same order of magnitude. In FDNPS, concrete is also the main source of K. On the other hand, Na is not measured 2/6 in every CsMP. In the first published papers, Na was not identified in EDX analysis as Zn and Na peaks overlap [START_REF] Okumura | Reactor environment during the Fukushima nuclear accident inferred from radiocaesium-bearing microparticles[END_REF]. The synthesised particles have a similar Na/Si ratio with CsMP, but it may also be possible for Na to be brought by other source such as sea water, if CsMP were generated after sea water injection. Thus, results on Al/Si, K/Si and Na/Si tend to confirm MCCI as generation process compared to other sources of Si. Fe concentration of synthesised particles is at least one order of magnitude below CsMP. According to thermodynamics calculations, the Fe fraction in the gas phase is directly influenced by the stainless steel fraction in the corium. This result suggests that the corium responsible for CsMP generation may have been richer in stainless steel, or that CsMP were generated at interfaces rich in stainless steel, if the melt contained heterogeneities. Finally, Cs concentration seems lower in synthesised particles than CsMP (one order of magnitude) but this may due to different effects. Cs is a volatile FP and there are different hypotheses on its behaviour before the core may have hit the concrete pedestal. Cs was probably mostly released from degraded fuel rods and may have condensed on colder walls and on the concrete pedestal. As for Fe, Cs concentration may have varied in the PCV. Plus, observed CsMP are isolated with Imaging Plates (IP), based on their radioactivity that is brought (mainly) by radiocaesium. Thus, studied CsMP are certainly not representative of all silicate aerosol particles in terms of size and Cs activity.

These experiments are a first milestone towards the synthesis of representative artificial CsMP and will be followed by other sets of trials to evaluate the influence of corium and atmosphere composition. Further analysis will also be carried out to study more precisely the concentration of key elements, to confirm if the matrix is amorphous SiO 2 and to study if the particle contains concentration gradients. Synthesis is accompanied by thermodynamic calculations. The comparison of CsMP observed in Japan with both modelling and particle synthesis under well-controlled conditions will provide a powerful help of using CsMP to assess accident evolution in Fukushima.

Figure 1 .

 1 Figure 1. (left) SEM image of a spherical particle collected at Tsukuba (Japan) in the days following the accident and (right) its associated EDX spectrum (black line) [3].

Figure 2 . 6 Figure 3 .

 263 Figure 2. Test section schematic view for aerosol generation inside the vessel.

Figure 4 .

 4 Figure 4. EDX spectra of two synthesised particles with a low background noise. Carbon is due to the coating used for sample preparation even though particles may contain carbon. Tungsten (W) is a pollution from the susceptor for induction coupling.

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 6


Carina Furusho-Percot

Klaus Goergen

Carl Hartick

Ketan Kulkarni

Jessica Keune

Stefan Kollet

Pan-European groundwater to atmosphere terrestrial systems climatology from a physically consistent simulation

come

Background & Summary

One of the main impacts of climate change highlighted by the 5th IPCC assessment report (AR5) is "the amplification of temperature extremes by changes in soil moisture" [START_REF] Jaeger | Impact of soil moisture-atmosphere coupling on European climate extremes and trends in a regional climate model[END_REF][START_REF] Hirschi | Observational evidence for soil-moisture impact on hot extremes in southeastern Europe[END_REF][START_REF] Taylor | Ground water and climate change[END_REF] , via a positive feedback mechanism that intensifies and increases the frequency of heat waves given the projected increase in summer drying conditions. The associated processes of the terrestrial water and energy cycle result from the interactions between the subsurface, the land surface and the atmosphere. These processes are essential to reproduce, predict and project climatic extreme events in simulations [START_REF] Seneviratne | Investigating soil moisture-climate interactions in a changing climate: A review[END_REF][START_REF] Dirmeyer | Evidence for Enhanced Land-Atmosphere Feedback in a Warming Climate[END_REF] . Because in most land surface models (LSMs) water transport and runoff has historically been treated in a simplified way, combined with free drainage lower boundary conditions in the subsurface, soil moisture states and fluxes and interactions between groundwater and soil moisture are biased with multiple impacts especially in areas with shallower groundwater, e.g., on the land-atmosphere coupling and the reproduction of extremes such as heat waves [START_REF] Vautard | The simulation of European heat waves from an ensemble of regional climate models within the EURO-CORDEX project[END_REF] . Recent LSM model improvements for regional climate models (RCMs) [START_REF] Barlage | The effect of groundwater interaction in North American regional climate simulations with WRF/Noah-MP[END_REF][START_REF] Schlemmer | A Groundwater and Runoff Formulation for Weather and Climate Models[END_REF] can lead to physically consistent interactions between the groundwater, the vadose zone, and the land-surface. Yet, many RCMs and global climate models (GCMs), contributing to CMIP5 [START_REF] Taylor | Ground water and climate change[END_REF] or CORDEX [START_REF] Gutowski | WCRP COordinated Regional Downscaling EXperiment (CORDEX): a diagnostic MIP for CMIP6[END_REF] still simplify these interactions. The AR5 acknowledges that the spread in regional climate projections over Europe is still substantial, due to large uncertainties related to natural heterogeneity and chaotic processes, but also due the inherent model structural deficiencies in fully representing two-way, non-linear feedbacks across the terrestrial system.

The dynamic feedbacks between the interacting compartments of the terrestrial system have been studied previously and corroborate the added value in coupling the respective compartment models to improve simulations [START_REF] Barlage | The effect of groundwater interaction in North American regional climate simulations with WRF/Noah-MP[END_REF] and forecasts. Research has focused on the interactions of the soil moisture state and the atmosphere [START_REF] Entekhabi | Mutual interaction of soil moisture state and atmospheric processes[END_REF] . In addition, the sensitivity of land surface fluxes on the depth of the groundwater table has been demonstrated [START_REF] Kollet | Capturing the influence of groundwater dynamics on land surface processes using an integrated, distributed watershed model[END_REF] , particularly for a critical water table depth of 1-5 m where the influence on energy balance is most pronounced, depending on soil heterogeneity and land use type. Similar effects of water table depths on land surface fluxes have been found 5 using an idealized simulation set-up to infer the effects of topography, land cover, atmospheric forcing and subsurface heterogeneity. A study [START_REF] Ferguson | Role of groundwater in watershed response and land surface feedbacks under climate change[END_REF] on the feedback between groundwater table depth and energy fluxes under changing climate conditions showed that such interactions depend on the prevailing hydrological conditions (energy limited versus moisture limited).

Unlike previous approaches, in which groundwater dynamics are usually not interacting with the atmosphere, terrestrial models such as the Terrestrial Systems Modeling Platform (TSMP) can provide a fully coupled representation of the terrestrial water and energy cycles. The impact of the representation of groundwater in regional climate simulations, has been demonstrated in a number of studies [START_REF] Shrestha | A Scale-Consistent Terrestrial Systems Modeling Platform Based on COSMO, CLM, and ParFlow[END_REF][START_REF] Sulis | Coupling Groundwater, Vegetation, and Atmospheric Processes: A Comparison of Two Integrated Models[END_REF] from the catchment to the continental scale. Previous TSMP simulations over Europe concentrated on the 2003 heat wave, showing a significant impact of groundwater states and the related land-atmosphere feedbacks [START_REF] Keune | Studying the influence of groundwater representations on land surface-atmosphere feedbacks during the European heat wave in 2003[END_REF] , and demonstrating far reaching impacts of human water use, beyond the local scale through atmospheric moisture transport [START_REF] Keune | Human Water Use Impacts on the Strength of the Continental Sink for Atmospheric Water[END_REF] . However, no physically consistent climatology of the coupled terrestrial hydrologic and energy cycles from the groundwater into the atmosphere is currently available.

In this study, TSMP is run for the European CORDEX domain [START_REF] Giorgi | Addressing Climate Information Needs at the Regional Level: the CORDEX Framework[END_REF] as a first step to establish a terrestrial systems climatology for the past decades, with a focus on a physically consistent representation of variably saturated groundwater and overland flow coupled with land surface and atmospheric processes. The dataset we present features daily simulation results since January 1989, but as some grid cells only reach the groundwater equilibrium in 1995, the period applicable for analysis consists of 23 water-years from September 1996 to August 2018 of all essential variables to describe the terrestrial water and energy cycles (Online-only Table 1). The TSMP-G2A data set is a valuable innovative data set to analyze and understand the mechanisms and interactions of water and energy in the terrestrial system including extreme events such as heat waves and droughts.

Methods

Data generation method -the terrestrial systems modeling platform (TSMP). The Terrestrial

System Modeling Platform, TSMP [START_REF] Shrestha | A Scale-Consistent Terrestrial Systems Modeling Platform Based on COSMO, CLM, and ParFlow[END_REF][START_REF] Gasper | Implementation and scaling of the fully coupled Terrestrial Systems Modeling Platform (TerrSysMP) in a massively parallel supercomputing environment – a case study on JUQUEEN (IBM Blue Gene/Q)[END_REF] version 1.1 is a scale-consistent fully coupled regional Earth system model, comprising the numerical weather prediction model COSMO version 5.01 [START_REF] Baldauf | Operational Convective-Scale Numerical Weather Prediction with the COSMO Model: Description and Sensitivities[END_REF] , the land surface model CLM version 3.5 [START_REF] Oleson | Improvements to the Community Land Model and their impact on the hydrological cycle[END_REF] and the surface-subsurface hydrologic model ParFlow [START_REF] Kollet | Integrated Surface-groundwater Flow Modeling: a Free-surface Overland Flow Boundary Condition in a Parallel Groundwater Flow Model[END_REF][START_REF] Ashby | A parallel multigrid preconditioned conjugate gradient algorithm for groundwater flow simulations[END_REF][START_REF] Jones | Newton-Krylov-multigrid solvers for large-scale, highly heterogeneous, variably saturated flow problems[END_REF] version 3.2. The models are externally coupled via the Ocean Atmosphere Sea Ice Soil (OASIS3) Model Coupling Toolkit (MCT) coupler [START_REF] Valcke | The OASIS3 coupler: a European climate modelling community software[END_REF] .

The COnsortium for Small Scale MOdelling (COSMO) model system is used by several meteorological services for operational numerical weather prediction (NWP) [START_REF] Baldauf | Operational Convective-Scale Numerical Weather Prediction with the COSMO Model: Description and Sensitivities[END_REF] and for climate change research as the COSMO Climate Limited area Modelling system (CCLM) [START_REF] Giorgi | Approaches to the simulation of regional climate change: A review[END_REF] . COSMO is a non-hydrostatic limited-area atmospheric model based on the primitive thermo-hydrodynamic Euler equations without scale-dependent approximations, describing fully-compressible flow in a moist atmosphere [START_REF] Baldauf | Operational Convective-Scale Numerical Weather Prediction with the COSMO Model: Description and Sensitivities[END_REF] . In COSMO, both adiabatic transport processes and diabatic processes, such as radiation, turbulence, cloud formation and precipitation are included. The prognostic atmospheric variables in this study encompass pressure, horizontal and vertical wind components, temperature, water vapour, cloud water, cloud ice, rain, snow and the turbulent kinetic energy. At land grid points, additional diagnostic variables, such as the 2 m air temperature and humidity and 10 m wind are provided.

In TSMP, the lower boundary information for COSMO is provided by the widely used Community Land Model (CLM). This boundary condition is composed of surface albedo, upward longwave radiation, sensible heat flux, latent heat flux, water vapor flux, and zonal and meridional surface stresses required by the atmospheric model [START_REF] Oleson | Improvements to the Community Land Model and their impact on the hydrological cycle[END_REF] . These variables are determined by diverse eco-hydrological processes simulated by CLM, such as root water uptake and transpiration by plants. In turn, CLM receives the short-and long-wave radiation, near-surface temperature, barometric pressure, specific humidity, wind speeds, and precipitation from COSMO at each grid point.

In TSMP, the surface water and groundwater flow are calculated by ParFlow. In the coupling, CLM provides the sources and sinks for soil moisture to ParFlow; these are precipitation throughfall and depth-differentiated (root) water uptake from evapotranspiration. In turn, in order to calculate the land surface water and energy balances, CLM receives from ParFlow spatially distributed soil moisture and soil matric potential, which are calculated by ParFlow based on Richards equation and the appropriate initial and boundary conditions in a continuum approach [START_REF] Kollet | Integrated Surface-groundwater Flow Modeling: a Free-surface Overland Flow Boundary Condition in a Parallel Groundwater Flow Model[END_REF][START_REF] Jones | Newton-Krylov-multigrid solvers for large-scale, highly heterogeneous, variably saturated flow problems[END_REF] . Surface runoff is calculated by a kinematic wave equation in ParFlow [START_REF] Kollet | Integrated surface-groundwater flow modeling: A free-surface overland flow boundary condition in a parallel groundwater flow model[END_REF] . This leads to a dynamic coupling of land surface processes and 3D variably saturated groundwater flow 3D heterogeneity in soil and hydrogeologic hydraulic properties.

The component models are coupled using OASIS3-MCT [START_REF] Shrestha | A Scale-Consistent Terrestrial Systems Modeling Platform Based on COSMO, CLM, and ParFlow[END_REF] , following a Multiple Program Multiple Data (MPMD) paradigm in an efficient parallel approach for massively parallel supercomputer environments [START_REF] Gasper | Implementation and scaling of the fully coupled Terrestrial Systems Modeling Platform (TerrSysMP) in a massively parallel supercomputing environment – a case study on JUQUEEN (IBM Blue Gene/Q)[END_REF] . Hence all simulations of this study are based on TSMP in fully coupled mode including ParFlow, CLM and COSMO.

Model setup. The model is set up over the European continent (Fig. 1), using a rotated latitude-longitude model grid with a horizontal resolution of 0.11° (12.5 km, termed as the "EUR-11" grid) from the COordinated Regional Downscaling EXperiment (CORDEX) project [START_REF] Giorgi | Addressing Climate Information Needs at the Regional Level: the CORDEX Framework[END_REF][START_REF] Jacob | EURO-CORDEX: new high-resolution climate change projections for European impact research[END_REF][START_REF] Gutowski | WCRP COordinated Regional Downscaling EXperiment (CORDEX): a diagnostic MIP for CMIP6[END_REF] , to ensure consistency in comparison with the ensemble of CORDEX RCM experiments (Table 1).

In this setup, CLM has 10 soil layers with a total depth of 3 m. These layers correspond to the 10 top layers of ParFlow, which has 5 additional layers with increasing thickness towards the bottom of the model domain reaching a total depth of 57 m to represent most of the active aquifers in Europe [START_REF] Gleeson | The global volume and distribution of modern groundwater[END_REF] . Deeper multi-story confined aquifer system and very deep basin flow at a time scale of hundreds to thousands of years is not accounted for in the model. Along the coastlines the boundary condition is defined as a constant hydraulic pressure with a hydrostatic profile based on a shallow water table of 0.05 m below the land surface. The topography in ParFlow is represented by D4 slopes calculated from the USGS GTOPO30 digital elevation data set, and the terrain following grid transform [START_REF] Maxwell | A terrain-following grid transform and preconditioner for parallel, large-scale, integrated hydrologic modeling[END_REF] with variable vertical discretization in order to improve the simulations for large topographic gradients and coarse lateral resolutions. The time step for ParFlow and CLM is 15 minutes, while COSMO runs with a 60 seconds time step. The coupling frequency between the component models is 15 minutes using averaged values from COSMO.

The hydraulic conductivity parameters for ParFlow are estimated [START_REF] Schaap | Using neural networks to predict soil water retention and soil hydraulic conductivity[END_REF] based on the soil texture taken from the Food and Agricultural Organization (FAO) database [START_REF]FAO/UNESCO soil map of the world: revised legend -UNESCO Digital Library[END_REF] . Fifteen different soil types condition the permeability, so that, e.g., grid cells with a soil dominated by clay have a vertical permeability of 0.062 m/hr, while for those composed mainly of sand, a vertical permeability of 0.27 m/hr is defined. The horizontal permeability values are scaled by a factor of 1000, following the scaling effect of the hydraulic parameter according to the grid resolution, resulting from the loss of information of the terrain curvature as consequence of spatial aggregation [START_REF] Fang | Scale dependent parameterization of soil hydraulic conductivity in 3D simulation of hydrological processes in a forested headwater catchment[END_REF] . The land cover data from the Moderate Resolution Imaging Spectroradiometer (MODIS [START_REF] Friedl | Global land cover mapping from MODIS: algorithms and early results[END_REF] ) data is used to define the plant functional types (PFT) for CLM. The leaf area index, the stem area index, and the monthly bottom and top heights of each PFT are calculated based on the global CLM surface data set [START_REF] Oleson | Improvements to the Community Land Model and their impact on the hydrological cycle[END_REF] . The COSMO model configuration resembles the settings of the CCLM community (https://www.clm-community.eu/).

In order to initialize the model with regard to land surface and subsurface hydrologic and energy states, a dynamic hydrologic equilibrium with the atmosphere must be obtained via a spinup of the model system (Fig. 2, top right boxes). In the spinup, the groundwater-land surface subsystem was simulated using ParFlow-CLM using a 1979-1989 climatologic atmospheric forcing derived from the ERA-Interim [START_REF] Dee | The ERA-Interim reanalysis: configuration and performance of the data assimilation system[END_REF] reanalysis. This forcing consists of an annual time series of 6-hourly time steps at each grid point, averaged over 11 years (1979-1989). The reanalysis data were retrieved from the European Centre for Medium-Range Forecasting (ECMWF) MARS archive. The ERA-Interim variables specific humidity, air temperature, 10 m wind speed, precipitation, long and short wave as well as the geopotential height at 0.7° lateral resolution at the lowest ERA-Interim model level were resampled to the EUR-11 grid of TSMP using the COSMO "int2lm" pre-processing software (Fig. 2, top left boxes). A stable dynamic equilibrium with regard to, e.g., soil moisture and groundwater states was achieved after running the ParFlow-CLM model system in a closed loop for 20 cycles. One cycle means one year simulation (January to December) driven by the above mentioned data set. After 20 cycles, the surface and subsurface model states converge and then constitute the initial surface and subsurface conditions for the fully coupled simulation starting from 1989-01-01. The model initialisation in 1989 makes the simulations compatible with the experiment protocol of the EURO-CORDEX RCM ensemble experiments. The ERA-Interim reanalysis data is also used for the COSMO model atmospheric initial and lateral boundary conditions for the EUR-11 domain throughout the fully coupled model simulations. In order to update the lateral boundaries more frequently than the available 00 and 12 UTC analyses, additional 3, 6, 9 and 15, 18 and 21 UTC forecasts from ERA-Interim were estimated by linear interpolation via the MARS retrieval system of ECMWF to inform the model every 3 h along the boundaries. TSMP is run transient from January 1989 to August 2018, with monthly restarts and no re-initializations of any compartment. Nudging is not used in order to let the evolution of feedback processes evolve freely.

The simulation workflow (Fig. 2) commences with the extraction of initial conditions (IC) and boundary conditions (BC) from ECMWF, followed by the pre-processing of the COSMO inputs with int2lm as a driver for the spin-up runs and as forcing data for the main TSMP simulations. The model spin-up of 20 cycles (years) is performed once before the actual climate simulations with TSMP (run TSMP in Fig. 2) can be launched. Concurrently to the model runs, TSMP outputs are continuously post-processed, analysed, visualized and stored at the Jülich Supercomputing Centre following a data-centric simulation and processing paradigm where data moving is kept to a minimum.

The raw outputs from the three component models are archived with 3 h frequency in monthly netCDF files. In addition to data format conversion (binary files from ParFlow to netCDF) and the reduction of the number of files by merging the data in monthly files, post processing also consists of temporal aggregation, calculating daily, monthly and seasonal temporal averages using primarily the Climate Data Operators (CDO, available at http:// www.mpimet.mpg.de/cdo). Boundary relaxation zones are removed from each side of the domain. In order to efficiently exchange data and as a means of data provenance tracking, final outputs are transferred to be as much as possible compliant with the CORDEX Archive Design, which in turn is derived from the CMIP specifications. In the process of "CMORization", data are stored using a predefined Data Reference Syntax (DRS) for the paths and filenames, and defined meta-data per variable as well as global attributes to describe the experiment. This ensures re-usability and interoperability.

Data records

The data set is available as netCDF V3 files without compression and is stored at a persistent data repository at the Jülich Supercomputing Centre 36 , as well as at PANGAEA [START_REF] Furusho | Pan-european, physically consistent simulations from groundwater to the atmosphere with the Terrestrial Systems Modeling Platform, TerrSysMP[END_REF] . The spatial resolution and grid specification corresponds to the EURO-CORDEX EUR-11 domain, according to the CORDEX data protocol specification (Version 3.1, 3 March 2014, http://is-enes-data.github.io/cordex_archive_specifications.pdf), with 424 × 412 grid elements on the rotated 0.11° grid. We provide time-series of daily means, aggregated into yearly files. The file Fig. 2 TSMP workflow for climate simulation experiments. Tasks and data flow are presented from the extraction of initial conditions (IC), atmospheric forcing for spin-up and boundary conditions (BC) every 3 h, through pre-processing COSMO inputs with int2lm, model spin-up, climate simulations with TSMP (run TSMP) down to the visualisation and analysis, also showing in which steps input and output data are stored on the Jülich Supercomputing Centre tape archive system ($ARCHIVE). Limitations. Due to the fact that the simulation was run transient after initialisation in 1989-01-01, without re-initializations, the model solution is expected to diverge from the forcing data as well as observations at the event scale. However, the regional anomalies compared to reference observational datasets show that the model captures the system dynamics and succession of dry/wet years, as well as heat waves and cold spells (Figs. 3 and4). Furthermore, the 12.5 km resolution is not high enough to explicitly resolve convection and the development of convective precipitation [START_REF] Prein | A review on regional convection-permitting climate modeling: Demonstrations, prospects, and challenges[END_REF][START_REF] Knist | Evaluation and projected changes of precipitation statistics in convection-permitting WRF climate simulations over Central Europe[END_REF] or the hydrology of smaller headwater catchments, including flash-flood prone watersheds.

technical Validation

The current experiment was designed to produce a near-natural climatology of the physical states of the terrestrial system, without the influence of, e.g., human water use. Accordingly, no real-world measurements are available for this type of system state for comparison and validation. Nevertheless, Figs. 3 and4 show that the model reproduces the succession of warm/cold and wet/dry seasons on the regional scale for the PRUDENCE analysis regions [START_REF] Christensen | A summary of the PRUDENCE model projections of changes in European climate by the end of this century[END_REF] (boxes in Fig. 1), compared to the one of the commonly used reference datasets for temperature and precipitation, the 0.25 degrees gridded European Climate Assessment and Dataset 41 (E-OBS v19, ECA&D). The Pearson's correlation values between the simulated and observed data series show good agreement in most European regions, with scores ranging from 0.73 to 0.94 for mean temperature anomalies and from 0.62 to 0.88 for precipitation anomalies. The time-series used for the validation period comprises 22 years from 01-01-1996 to 31-12-2018, because the model had not reached full groundwater states equilibrium in all grid cells until 1995.

The total column water storage simulated by TSMP was assessed by comparing to the observations of GRACE [START_REF] Watkins | Improved methods for observing Earth's time variable mass distribution with GRACE using spherical cap mascons[END_REF] (Fig. 5). The total column water storage i, j (L) from the land surface to the bottom of the aquifer constitutes an integrated measure of water resources calculated as follows [START_REF] Hartick | probabilistic prediction of water resources over Europe following the heatwave and drought[END_REF] in Eq. ( 1): where sat i,j,k is the relative saturation (-), por i,j,k the porosity (-) for a pixel with indices i, j, k in the lateral and vertical direction, respectively, dz k is the extent of a vertical grid cell (L) and nz is the number of grid cells in the vertical direction. Monthly anomalies were calculated for each pixel and then within each PRUDENCE region.

Figure 5 shows that the column water storage simulated by TSMP is in good agreement with the GRACE data in most PRUDENCE regions, but there are discrepancies in the Alpine region (AL) as well as in Scandinavia (SC).

The model capability of reproducing water storage and water table depth have been discussed in previous studies focusing on the European heat wave of 2003 [START_REF] Keune | Studying the influence of groundwater representations on land surface-atmosphere feedbacks during the European heat wave in 2003[END_REF][START_REF] Keune | Human Water Use Impacts on the Strength of the Continental Sink for Atmospheric Water[END_REF] . The overall WTDs simulated with TSMP are comparable to the WTD composition by an observation based global gridded model of WTD [START_REF] Fan | Global Patterns of Groundwater Table Depth[END_REF] with large-scale patterns, following the terrain, representing a shallow WTD along the coastlines and in arid valleys and also inundated wetlands in lowland regions, e.g., Netherlands [START_REF] Keune | Studying the influence of groundwater representations on land surface-atmosphere feedbacks during the European heat wave in 2003[END_REF] .

Usage Notes

As most climate data in netCDF, starting with a quick visualization can be easily achieved with any netCDF viewer such as ncview (http://meteora.ucsd.edu/~pierce/ncview_home_page.html), meta data of the file may be best viewed using the ncdump command; a list of software tools and libraries for using netCDF is available from the developers of the netCDF format at UCAR (https://www.unidata.ucar.edu/software/netcdf/software.html). The CDO software is a collection of operators for standard processing of climate model data and can be directly used to work with this dataset taking into account the spatial reference of the data as well as the temporal information. The application is straightforward and allows a wide range of calculations from space-time aggregation to sophisticated climate index calculations. For more personalized analysis and visualization, we also recommend using Python with specific libraries such as Pandas or xarray. Codes created specifically for post-processing TSMP are also available with the TSMP release version. post-processing tools. TSMP is essentially released without its component models, i.e., the release contains the built system, all configuration files, such as namelists, for the sample cases, the component model code patches and all coupler related modifications. The user must download the component models from their respective separate repositories: All ParFlow releases are available via GitHub (https://github.com/parflow/parflow). The official CLM website (http://www.cgd.ucar.edu/tss/clm/distribution/clm3.5/index.html) offers all links to

Fig. 1

 1 Fig. 1 Water table depth [m] climatology from September 1st 1996 to August 31st 2018, represented within the EURO-CORDEX domain (412 × 424 grid cells). The black boxes correspond to the PRUDENCE regions, for which the data time-series validation has been performed.

  names are structured according to the Data Reference Syntax as defined by the EURO-CORDEX archive design: <variable>_<spatial resolution>_<boundary conditions dataset>_<period>_<run identification>_<insti-tute>_<model>_<data version>_<time step>_<initial time step>_<final time step>. For example, the file clw_EUR-11_ECMWF-ERAINT_evaluation_r1i1p1_FZJ-IBG3-TSMP11_v1_ day_20070101-20071231.nc is the vertical integrated cloud ice variable, at the EUR-11 resolution (12.5 km). The run used ECMWF ERA-Interim data, ensemble member r1i1p1, as boundary conditions during the evaluation period, performed at the Research Centre Jülich (FZJ) at IBG-3 Institute, using TSMP version 1.1. It corresponds to the first data-set version (v1), and the file contains daily values between 2007-01-01 and 2007-12-31. Each self-describing file also contains the definition of the geographical coordinate system of the grid (latitudes, longitudes and rotated pole).

Fig. 3

 3 Fig. 3 Seasonal anomalies of the simulated (EVAL) 2 m air temperature compared to the E-OBS v19 dataset averaged over each PRUDENCE region. The gray line represents E-OBS v19 dataset whereas the continuous red line represents TSMP simulated data and the green dashed line, ERA-Interim data. The corresponding sample covariance or cross-correlation (CORR) values with no lag time follow the PRUDENCE region code (BI -British Isles, IB -Iberian Peninsula, FR -France, ME -Mid Europe, SC -Scandinavia, AL -Alps, MD -Mediterranean and EA -Eastern Europe, see Fig. 1).

Fig. 4

 4 Fig.4 Seasonal anomalies of the simulated (EVAL) precipitation (mm) compared to the E-OBS v19 dataset and ERA-Interim over each PRUDENCE region. As in Fig.3, only for precipitation instead of temperature data.

Fig. 5

 5 Fig.5 Storage anomalies s calculated for the entire soil column including soil water, ss, and aquifer, as storages (ss + as) and surface water storage (ss + as + sws) on the time period used on the GRACE mascon data set, 2003-2011, over each PRUDENCE region (Fig.1).

Table 1 .

 1 Model

		ParFlow	CLM	COSMO
	Horizontal grid specifications (number of grid points)	436 × 424	436 × 424	444 × 436
	Horizontal resolution	0.11°0.11°0.11°V
	ertical levels	15	10	50
	Vertical resolution	variable	variable	variable
	Depth/height	57 m	3 m	22 km
	Time step	900 s	900 s	60 s

setup of TSMP over the EURO-CORDEX EUR-11 domain. ParFlow and CLM use the same equal-area rotated standardized latitude-longitude grid as COSMO. Please note the grid specification here is including the lateral boundary relaxation zone. The EUR-11 grid mandatory focus area is 424 × 412 grid elements.

Scientific Data | (2019) 6:320 | https://doi.org/10.1038/s41597-019-0328-7

Code availability

Stable release versions of TSMP are provided through a git development repository available at the model's website (https://www.terrsysmp.org). The release version includes extensive instructions for installing the system, including sample reference test cases for typical application examples, as well as a suite of pre-processing and

acknowledgements

The authors gratefully acknowledge the computing time granted through JARA-HPC and the VSR commission on the supercomputer JURECA at Forschungszentrum Jülich through compute time projects cjibg33 and cjibg35. The work described in this paper has received funding from the Initiative and Networking Fund of the Helmholtz Association (HGF) through the project "Advanced Earth System Modelling Capacity (ESM)". The content of the paper is the sole responsibility of the author(s) and it does not represent the opinion of the Helmholtz Association, and the Helmholtz Association is not responsible for any use that might be made of the information contained.

Author contributions

Conceived and designed the experiments: J.K., K.K. and S.K. Performed the experiments: C.F. and K.K. Analyzed the data: C.F., S.K., K.G. and C.H. Contributed with analysis tools: J.K., Wrote the paper: C.F., K.G. and S.K.

Competing interests

The authors declare no competing interests.

Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


PRELIMINARY DATA OF REPTILES AND AMPHIBIANS FROM EL SALT Xb (MIDDLE PALAEOLITHIC, ALCOY, SPAIN): PALAEOCLIMATIC IMPLICATIONS

The locality of El Salt (Middle Paleolithic, Alcoy, Spain) is mainly known by having one of the youngest Neanderthals records of the Southeastern Iberian Peninsula. The upper part of stratigraphic unit Xb, dated at 52.3 ± 4.6 ka (MIS 3), is characterized by the presence of several archaeological assemblages, comprising vertebrate faunal remains, lithics elements and anthropogenically modified cobbles. The stratigraphic column of El Salt consists of 6.3 mthick of sediments divided in 13 lithostratigraphic units [START_REF] Fumanal | El yacimiento musteriense de El Salt (Alcoi, País Valenciano). Rasgos geomorfológicos y climatoestratigrafía de sus registros[END_REF]. The field campaign of 2013 in unit Xb, have yielded for the first time in this locality a small sample of amphibian and reptiles remains

The faunal list for unit Xb is composed by: three taxa of anurans (Alytes obstetricans; Bufo bufo sensu lato and Epidalea calamita), one taxon of blanid (Blanus cinereus sensu lato), two taxa of lizards (Chalcides bedriagai and cf.

Acanthodactylus erythrurus) and one taxon of snakes (cf.

Rhinechis scalaris).

Marquina, R. 1,2, , * Gamonal, A. 1 , Fagoaga, A. 1,2 , Crespo, V. D. 1,2 , Ruiz-Sánchez, F. J. 1,2,3 , Bailon, S. 4,5 , Hernández, C. M. 6 , & Galván, B. 6 * rafael.marquina@uv.es In order to reconstruct the climate at the moment of formation of the unit, we studied the current distribution of the reptiles and amphibians species described by using

Fig. 1 .

 1 Fig. 1. A, Geographical location of El Salt archaeological site. B, General view of the locality. C, Stratigraphic column of El Salt showing the different litostratigraphic units described by Fumanal (1994).

Fig. 2 .

 2 Fig. 2. Palaeoherpetological remains from El Salt Xb. A) Alytes obstetricans, left humerus. B) Bufo bufo, s. l., left humerus. C) Epidalea calamita. a, right scapula, b, left ilim). D) Blanus cinereus, s. l., left dentary. E) Chalcides bedriagai. a, right premaxilla, b, right dentary. F) cf. Acanthodactylus erythrurus. a, premaxilla, b, right pterygoid, c, right dentary. G) cf. Rhinechis scalaris, dorsal vertebra in dorsal (right) and ventral (left) view. Scale bars equal to 1 mm for amphibians and 0.5 for reptiles. Images of live animals taken from Wikimedia Commons.

  b

ACKNOWLEDGEMENTS

The present work was supported by the Sociedad Española de Paleontología (SEP) grant (Ayuda a la Investigación de la SEP 2015-2016 003 "La herpetofauna fósil como herramienta para la reconstrucción paleoclimática: el caso de El Salt (nivel Xb, Paleolítico medio; Alcoy, Alicante)").