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This work improves the characterization and knowledge of the surface wind climatology over Europe with the development of an observational database with unprecedented quality control (QC), the European Surface Wind Observational database (EuSWiO). EuSWiO includes more than 3,829 stations with sub-daily resolution for wind speed and direction, with a number of sites spanning the period of 1880–2017, a few hundred time series starting in the 1930s and relatively good spatial coverage since the 1970s. The creation of EuSWiO entails the merging of eight different data sets and its submission to a common QC. About 5% of the total observations were flagged, correcting a great part of the extreme and unrealistic values, which have a discernible impact on the statistics of the database. The daily wind variability was characterized by means of a classification technique, identifying 11 independent subregions with distinct temporal wind variability over the 2000–2015 period. Significant decreases in the wind speed during this period are found in five regions, whereas two regions show increases. Most regions allow for extending the analysis to earlier decades. Caution in interpreting long-term trends is needed as wind speed data have not been homogenized. Nevertheless, decreases in the wind speed since the 1980s can be noticed in most of the regions. This work contributes to a deeper understanding of the temporal and spatial surface wind variability in Europe. It will allow from meteorological to climate and climate change studies, including potential applications to the analyses of extreme events, wind power assessments or the evaluation of reanalysis or model-data comparison exercises at continental scales.

© 2010 American Meteorological Society. The National Center for Atmospheric Research is sponsored by the National Science Foundation.This project was accomplished within the Collaboration Agreement 09/153 between UCM and CIEMAT, and it was partially funded by Project CGL2005-06966-C07/CLI. We thank the Navarra Government for providing us with the wind dataset used in this study and ECMWF for free access to its datasets. An initial version of the wavelet software was provided by C. Torrence and G. Compo (available online at http:// atoc.colorado.edu/research/). We also thank the three reviewers for their helpful comments., This study analyzes the daily-mean surface wind variability over an area characterized by complex topography through comparing observations and a 2-km-spatial-resolution simulation performed with the Weather Research and Forecasting (WRF) model for the period 1992-2005. The evaluation focuses on the performance of the simulation to reproduce the wind variability within subregions identified from observations over the 1999-2002 period in a previous study. By comparing with wind observations, the model results show the ability of the WRF dynamical downscaling over a region of complex terrain. The higher spatio-temporal resolution of the WRF simulation is used to evaluate the extent to which the length of the observational period and the limited spatial coverage of observations condition one's understanding of the wind variability over the area. The subregions identified with the simulation during the 1992-2005 period are similar to those identified with observations (1999-2002). In addition, the reduced number of stations reasonably represents the spatial wind variability over the area. However, the analysis of the full spatial dimension simulated by the model suggests that observational coverage could be improved in some subregions. The approach adopted here can have a direct application to the design of observational networks., National Science Foundation (NSF), Universidad Complutense de Madrid (UCM), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Meteorological Society. This investigation was partially supported by Projects CGL-2008-05093/CLI and CGL-2011-29677-C02 and was accomplished within the Collaboration Agreement 09/490 between CIEMAT and NCAR as well as the Collaboration Agreement 09/153 between CIEMAT and UCM. NCAR is sponsored by the National Science Foundation. We thank the Navarra government for providing us with the observations used in this study. Discussion with Fei Chen and Peggy Lemone were helpful during this work. The authors would also like to thank Maria Tombrou for her comments regarding the similarity functions in unstable conditions. We would also like to thank the reviewers for their constructive comments., This study summarizes the revision performed on the surface layer formulation of the Weather Research and Forecasting (WRF) model. A first set of modifications are introduced to provide more suitable similarity functions to simulate the surface layer evolution under strong stable/unstable conditions. A second set of changes are incorporated to reduce or suppress the limits that are imposed on certain variables in order to avoid undesired effects (e. g., a lower limit in u_*). The changes introduced lead to a more consistent surface layer formulation that covers the full range of atmospheric stabilities. The turbulent fluxes are more (less) efficient during the day (night) in the revised scheme and produce a sharper afternoon transition that shows the largest impacts in the planetary boundary layer meteorological variables. The most important impacts in the near-surface diagnostic variables are analyzed and compared with observations from a mesoscale network., National Science Foundation (NSF), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Universidad Complutense de Madrid (UCM), National Center for Atmospheric Research (NCAR), Depto. de Física Teórica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 American Meteorological Society. This project was accomplished within the collaboration agreement 091153 between UCM and CIEMAT, and it was partially funded by projects CGL2005-06966-C07/CLI and PSE-120000-2008-9 We thank the Navarra Government for providing us with the wind dataset used in this study. We also like to thank the reviewers for their helpful comments., Meteorological data of good quality arc important for understanding both global and regional climates In this respect, great efforts have been made to evaluate temperature- and precipitation-related records This study summarizes the evaluations made to date of the quality of wind speed and direction records acquired at 41 automated weather stations in the northeast of the Iberian Peninsula Observations were acquired from 1992 to 2005 at a temporal resolution of 10 and 30 min A quality assurance system was imposed to select) the records for 1) manipulation errors associated with storage and management of the data. 2) consistency limits to to ensure that observations ale within their natural limits of variation, and 3) temporal consistency to assess abnormally low/high variations in the individual time series In addition. the most important biases of the dataset are analyzed and corrected wherever possible A total of 1 8% wind speed and 3 7% wind direction records was assumed invalid. pointing to specific problems in wind measurement The study not only tiles to contribute to the science with the creation of a wind damsel of unmoved quality. but it also reports on potential errors that could be plc:sent in other wind datasets, Universidad Complutense de Madrid (UCM), Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Meteorological Society. The National Center for Atmospheric Research is sponsored by the National Science Foundation.We thank the Navarra government and the ECMWF for providing us with the datasets used in this study. This investigation was partially supported by Projects CGL-2008-05093/CLI and PSE-120000-2008-9 and was accomplished within the Collaboration Agreement 09/490 between CIEMAT and NCAR as well as the Collaboration Agreement 09/153 between CIEMAT and UCM. We also thank the reviewers for their helpful comments., Variations in the diurnal wind pattern associated with heat waves and drought conditions are investigated climatologically at a regional level (northeast of the Iberian Peninsula). The study, based on high-density observational evidence and fine spatial-scale mesoscale modeling for the 1992-2004 period, shows that wind speed can decrease up to 22% under situations characterized by extremely high temperatures and severe drought, such as the European summer of 2003. By examining the role of the different atmospheric scales of motion that determine the wind diurnal variability, it is found that the 2003 synoptic conditions are the main driver for changes in the wind speed field. In turn, these changes are modulated by mesoscale circulations influenced by the soil moisture availability. The results have implications for broad regional modeling studies of current climate and climate change simulations in as much as the study demonstrates that a correct representation of local soil moisture conditions impacts atmospheric circulation and therefore the regional climate state., National Science Foundation, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), España, National Center for Atmospheric Research (NCAR), EE.UU., Universidad Complutense de Madrid (UCM), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

The land is a pivotal component of the Earth and its climate system since many processes of natural variations in the climate system, which affect the environment and human society, are governed by the land surface. Hence, a good representation of the thermal and hydrological states of the land surface in climate models is important to have a realistic simulation of the coupling between the atmosphere and the lito-biosphere. An influencing factor for improving the realism of the ground energy and water balance in climate models is the depth of the land zero-flux Bottom Boundary Condition Placement (BBCP). Despite recent improvements in modeling land surface processes in climate models, only limited attention has been directed toward the effect of the BBCP in Land Surface Models (LSMs) and its impact on the representation of terrestrial thermodynamics. Previous analytical and modeling studies suggest that the simulation of subsurface thermodynamics in current-generation climate models is not accurate due to the zero-heat-flux BBCP being imposed too close to the surface. An insufficiently deep land component in current-generation climate models compromises the simulation of the terrestrial thermal state and can influence land-atmosphere interactions. Further improvements in LSMs relate to the representation and sensitivity of coupling processes between the ground thermodynamic and hydrological regimes. As moisture is one of the main drivers of near-surface climate interactions, the hydro-thermodynamic coupling is crucial for studying the impacts of perturbations caused by human activity. Under climate change conditions, some areas and ecosystems are more vulnerable to a rapidly warming world than others..., El suelo es un componente fundamental de la Tierra y su sistema climático, ya que muchos procesos de variabilidad natural en el sistema climático, que afectan al medio ambiente y la sociedad humana, se rigen por lo que ocurre en la superficie terrestre. Por lo tanto, una buena representación de los estados térmicos e hidrológicos de la superficie terrestre en los modelos climáticos es importante para tener una simulación realista del acoplamiento entre la atmósfera y la lito-biosfera. Un factor que influye en la mejora del realismo de la energía del suelo y el equilibrio hídrico en los modelos climáticos es la profundidad de la posición de la condición de contorno del fondo (BBCP) de la tierra. Los estudios anteriores sugieren que la simulación dela termodinámica del subsuelo en los modelos climáticos de la generación actual no es precisa debido a que el BBCP de flujo de calor cero se impone demasiado cerca de la superficie. Una componente terrestre insuficientemente profunda en los modelos climáticos compromete la simulación del estado térmico terrestre y puede influir en las interacciones tierra-atmósfera. Otras mejoras en los LSM se relacionan con la representación y la sensibilidad de los procesos de acoplamiento entre los regímenes hidrológico y termodinámico del suelo. Dado que la humedad es uno delos principales impulsores de las interacciones climáticas cercanas a la superficie, el acoplamiento hidro-termodinámico es crucial para estudiar los impactos de las perturbaciones causadas por la actividad humana. En condiciones de cambio climático, algunos hábitats y ecosistemas son más vulnerables que otros en un mundo que se calienta rápidamente en un contexto de vertiginoso cambio global...

© 2022 Royal Meteorological Society. We gratefully acknowledge the IlModels (CGL2014-59644-R) and GreatModelS (RTI2018-102305-B-C21) projects. We also thank the Spanish Meteorological Agency (AEMET) for the data. The ERA5-Land reanalysis used in this work is funded under the Copernicus Regulation and operated by ECMWF under the ECMWF Agreement. Francisco José Cuesta-Valero is funded by the Alexander von Humboldt Foundation. FUNDING INFORMATION Ministerio de Economía, Industria y Competitividad, Grant/ Award Number: BES-2015-075019; Ministerio de Ciencia, Innovación y Universidades, RTI2018-102305-B-C21., Understanding the near-surface soil thermal regime and its connection to the atmospheric state is important for the assessment of several climate-related processes. However, the lack of in situ soil temperatures measurements limits the analysis of such processes. In this study, we have developed a quality-controlled soil temperature database for Spain that consists of 39 sites spanning from 1987 to 2018. We have used this database to assess the near-surface soil thermal regime. Likewise, we evaluate at seasonal to multidecadal timescales the land-air temperature coupling over Spain by analysing the structure of the surface air temperature (SAT) and the ground surface temperature (GST) covariance and also their long-term evolution. In addition, we have employed the ERA5-Land reanalysis to test the consistence between observations and reanalysis. The results show that the near-surface soil thermal structure is dominated by conduction despite some influence of hydrology-related processes. Regarding the land-air temperature coupling, we have found a strong connection between SAT and GST. However, in the summer months there is an offset in SAT-GST at some sites due to limited evaporation and enhanced sensible heat fluxes. Furthermore, multidecadal SAT-GST decoupling may exist over some sites as a response to decreasing precipitation. The ERA5-Land represents the observations' climatology well, but it underestimates the summer soil temperature observations and the long-term trends at some sites., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Ministerio de Economía, Industria y Competitividad (MINECO), Copernicus Regulation, operated by ECMWF under the ECMWF Agreement, Alexander von Humboldt Foundation, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

This research has been supported by the Canadian Network for Research and Innovation in Machining Technology, Natural Sciences and Engineering Research Council of Canada (grant no. DG 140576948), the Canada Excellence Research Chairs, Government of Canada (grant no. 230687), and the Canada Foundation for Innovation (CFI)., Understanding the differences between regional simulations of land-atmosphere interactions and near-surface conditions is crucial for a more reliable representation of past and future climate. Here, we explore the effect of changes in the model's horizontal resolution on the simulated energy balance at the surface and near-surface conditions using the Weather Research and Forecasting (WRF) model. To this aim, an ensemble of 12 simulations using three different horizontal resolutions (25, 50 and 100 km) and four different land surface model (LSM) configurations over North America from 1980 to 2013 is developed. Our results show that finer resolutions lead to higher surface net shortwave radiation and maximum temperatures at mid and high latitudes. At low latitudes over coastal areas, an increase in resolution leads to lower values of sensible heat flux and higher values of latent heat flux, as well as lower values of surface temperatures and higher values of precipitation, and soil moisture in summer. The use of finer resolutions leads then to an increase in summer values of latent heat flux and convective and non-convective precipitation and soil moisture at low latitudes. The effect of the LSM choice is larger than the effect of horizontal resolution on the near-surface temperature conditions. By contrast, the effect of the LSM choice on the simulation of precipitation is weaker than the effect of horizontal resolution, showing larger differences among LSM simulations in summer and over regions with high latent heat flux. Comparison between observations and the simulation of daily maximum and minimum temperatures and accumulated precipitation indicates that the CLM4 LSM yields the lowest biases in maximum and minimum mean temperatures but the highest biases in extreme temperatures. Increasing horizontal resolution leads to larger biases in accumulated precipitation over all regions particularly in summer. The reasons behind this are related to the partition between, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2022). © 2022 The Authors. CRL was supported by the NEWA ERANET project (PCIN-2014-015-C07-06, PCIN-2016-009) and 18 ROJAS-LABANDA ET AL. GReatModelS RTI2018-102305- B-C21 from MINECO. This research has been conducted under the Joint Research Unit between UCM and CIEMAT, by the Collaboration Agreement 7158/ 2016. We acknowledge the data providers in the ECA&D project, the Royal Netherlands Meteorological Institute, the Swedish Meteorological and Hydrological Institute, the Deutscher Wetterdienst and the National Center for Atmospheric Research. Initial and future versions of the EuSWiO will be made available under the European Climate Assessment & Dataset (www.ecad.eu)., This work improves the characterization and knowledge of the surface wind climatology over Europe with the development of an observational database with unprecedented quality control (QC), the European Surface Wind Observational database (EuSWiO). EuSWiO includes more than 3,829 stations with sub-daily resolution for wind speed and direction, with a number of sites spanning the period of 1880–2017, a few hundred time series starting in the 1930s and relatively good spatial coverage since the 1970s. The creation of EuSWiO entails the merging of eight different data sets and its submission to a common QC. About 5% of the total observations were flagged, correcting a great part of the extreme and unrealistic values, which have a discernible impact on the statistics of the database. The daily wind variability was characterized by means of a classification technique, identifying 11 independent subregions with distinct temporal wind variability over the 2000–2015 period. Significant decreases in the wind speed during this period are found in five regions, whereas two regions show increases. Most regions allow for extending the analysis to earlier decades. Caution in interpreting long-term trends is needed as wind speed data have not been homogenized. Nevertheless, decreases in the wind speed since the 1980s can be noticed in most of the regions. This work contributes to a deeper understanding of the temporal and spatial surface wind variability in Europe. It will allow from meteorological to climate and climate change studies, including potential applications to the analyses of extreme events, wind power assessments or the evaluation of reanalysis or model-data comparison exercises at continental scales., Ministerio de Ciencia e Innovación (MICINN), Ministerio de Ciencia e Innovación (MICINN), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2021 American Meteorological Society. L Thanks to R. Schnur and V. Gayler from MPI Hamburg. We gratefully acknowledge the IlModels (CGL2014-59644-R) and GreatModelS (RTI2018102305-B-C21 and RTI2018-102305-A-C22) projects funded by the Spanish MINECO. SH contributed in the frame of the ERANET-plus-Russia project SODEEP (Study Of the Development of Extreme Events over Permafrost areas) supported by BMBF (Grant 01DJ18016A). This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID bm1026., The representation of the thermal and hydrological states in land surface models is important for a realistic simulation of land-atmosphere coupling processes. The available evidence indicates that the simulation of subsurface thermodynamics in Earth system models is inaccurate due to a zero-heat-flux bottom boundary condition being imposed too close to the surface. To assess the influence of soil model depth on the simulated terrestrial energy and subsurface thermal state, sensitivity experiments have been carried out in piControl, historical, and RCP scenarios. A deeper bottom boundary condition placement has been introduced into the JSBACH land surface model by enlarging the vertical stratification from 5 to 12 layers, thereby expanding its depth from 9.83 to 1416.84 m. The model takes several hundred years to reach an equilibrium state in stand-alone piControl simulations. A depth of 100 m is necessary, and 300 m recommendable, to handle the warming trends in historical and scenario simulations. Using a deep bottom boundary, warming of the soil column is reduced by 0.5 to 1.5 K in scenario simulations over most land areas, with the largest changes occurring in northern high latitudes, consistent with polar amplification. Energy storage is 3-5 times larger in the deep than in the shallow model and increases progressively with additional soil layers until the model depth reaches about 200 m. While the contents of Part I focus on the sensitivity of subsurface thermodynamics to enlarging the space for energy, Part II addresses the sensitivity to changing the space for water and improving hydrological and phase-change interactions., Ministerio de Economía y Competitividad (MINECO), BMBF Federal Ministry of Education & Research, Scientific Steering Committee (WLA), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

This work was supported by the projects IlModelS, project no. CGL2014-726 59644-R and GReatModelS, project no. RTI2018-102305-B-C21. The work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID bm1026. Vladimir Alexeev was supported by the Interdisciplinary Research for Arctic Coastal Environments (InteRFACE) project through the Department of Energy, Office of Science, Biological and Environmental Research Program's Regional and Global Model Analysis program, and by NOAA project NA18OAR4590417. We also wish to thank Veronika Gayler for technical support on JSBACH and Christian Reick for helpful comments and discussion., Previous analytical and simulation-based analyses suggest that deeper land surface models are needed to realistically simulate the terrestrial thermal state in climate models, with implications for land-atmosphere interactions. Analytical approaches mainly focused on the subsurface propagation of harmonics such as the annual temperature signal, and a direct comparison with climate-change model output has been elusive. This study addresses the propagation of a harmonic pulse fitted to represent the timescale and amplitude of anthropogenic warming. Its comparison to land model simulations with stepwise increased bottom boundary depth leads to an agreement between the simulation-based and analytical frameworks for long-term climate trends. Any depth increase gradually decreases the relative error in the subsurface thermodynamics, and a minimum depth of 170 m is recommended to simulate the ground climate adequately. The approach provides an accurate estimate of the required land-model depth for climate-change simulations and assesses the relative bias in insufficiently deep land models. Plain Language Summary Many current-generation climate models have land components that are too shallow. Under climate change conditions, the long-term warming trend at the surface propagates deeper into the ground than the commonly used 3-10 m. Shallow models alter the terrestrial heat storage and distribution of temperatures in the subsurface, influencing the simulated land-atmosphere interactions. Previous studies focusing on annual timescales suggest that deeper models are required to match subsurface-temperature observations and the classic analytical heat conduction solution. However, for a systematic investigation of land-model deepening in the frame of anthropogenic climate change, the classic analytical solution is inaccurate because it does not mimic the timescale and amplitude of the simulated warming trend. This study intends to bridge the gap between analytical and simulatio, Ministerio de Economía y Competitividad (MINECO), Scientific Steering Committee (WLA), Interdisciplinary Research for Arctic Coastal Environments (InteRFACE) project through the Department of Energy, Office of Science, Biological and Environmental Research Program's Regional and Global Model Analysis program, NOAA project, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2021 American Meteorological Society. We gratefully acknowledge the IlModelS (CGL2014-59644-R) and GreatModelS (RTI2018-102355505B-C21 and RTI2018-102305-A-C22) projects. Stefan Hagemann contributed in the frame of the ERANET-plus-Russia project SODEEP (Study Of the Development of Extreme Events over Permafrost areas) supported by BMBF (Grant 01DJ18016A). This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted by its Scientific Steering Committee (WLA) under project ID bm1026. We also wish to thank Veronika Gayler for technical support on JSBACH., The impact of various modifications of the JSBACH land surface model to represent soil temperature and cold-region hydro-thermodynamic processes in climate projections of the twenty-first century is examined. We explore the sensitivity of JSBACH to changes in the soil thermodynamics, energy balance and storage, and the effect of including freezing and thawing processes. The changes involve 1) the net effect of an improved soil physical representation and 2) the sensitivity of our results to changed soil parameter values and their contribution to the simulation of soil temperatures and soil moisture, both aspects being presented in the frame of an increased bottom boundary depth from 9.83 to 1418.84 m. The implementation of water phase changes and supercooled water in the ground creates a coupling between the soil thermal and hydrological regimes through latent heat exchange. Momentous effects on subsurface temperature of up to +/- 3 K, together with soil drying in the high northern latitudes, can be found at regional scales when applying improved hydro-thermodynamic soil physics. The sensitivity of the model to different soil parameter datasets is relatively low but shows important implications for the root zone soil moisture content. The evolution of permafrost under preindustrial forcing conditions emerges in simulated trajectories of stable states that differ by 4-6 x 10(6) km(2) and shows large differences in the spatial extent of 10(5)-10(6) km(2) by 2100, depending on the model configuration., Ministerio de Economía y Competitividad (MINECO), BMBF Federal Ministry of Education & Research, Scientific Steering Committee (WLA), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Author(s) 2021. We are grateful for two anonymous reviewers and their thoughtful and constructive feedback. This analysis contributes to the PALEOLINK project (http://pastglobalchanges. org/science/wg/2knetwork/projects/paleolink/intro, last access: 16 February 2021), part of the PAGES 2k Network. Hugo Beltrami was supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs Program, and the Canada Foundation for Innovation. Hugo Beltrami holds the Canada Research Chair in Climate Dynamics. Almudena García-García and Francisco José Cuesta-Valero were funded by Hugo Beltrami’s Canada Research Chair program, the School of Graduate Students at the Memorial University of Newfoundland, and the Research Office at St. Francis Xavier University. This research has been supported by the Natural Sciences and Engineering Research Council of Canada (grant no. NSERC DG 140576948) and the Canada Research Chairs (grant no. CRC 230687)., Energy exchanges among climate subsystems are of critical importance to determine the climate sensitivity of the Earth’s system to greenhouse gases, to quantify the magnitude and evolution of the Earth’s energy imbalance, and to project the evolution of future climate. Thus, ascertaining the magnitude of and change in the Earth’s energy partition within climate subsystems has become urgent in recent years. Here, we provide new global estimates of changes in ground surface temperature, ground surface heat flux, and continental heat storage derived from geothermal data using an expanded database and new techniques. Results reveal markedly higher changes in ground heat flux and heat storage within the continental subsurface than previously reported, with land temperature changes of 1 K and continental heat gains of around 12 ZJ during the last part of the 20th century relative to preindustrial times. Half of the heat gain by the continental subsurface since 1960 has occurred in the last 20 years., Natural Sciences and Engineering Research Council of Canada, Canada Research Chairs Program, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Global Forecasters S.L. provided part of the funding for this research. Additionally, the study was partly funded by the project "GReatModelS-Global and Regional Impacts of using more realistic Land Modelling on Historical and Climate Change scenario Simulations (refs. RTI2018102305-A-C22 and RTI2018-102305-B-C21)" funded by the Spanish Government (Ministerio de Ciencia, Innovación y Universidades)., Estimating the probability of the occurrence of hazardous winds is crucial for their impact in human activities; however, this is inherently affected by the shortage of observations. This becomes critical in poorly sampled regions, such as the northwestern Sahara, where this work is focused. The selection of any single methodological variant contributes with additional uncertainty. To gain robustness in the estimates, we expand the uncertainty space by applying a large body of methodologies. The methodological uncertainty is constrained afterward by keeping only the reliable experiments. In doing so, we considerably narrow the uncertainty associated with the wind return levels. The analysis suggest that not necessarily all methodologies are equally robust. The highest 10-min speed (wind gust) for a return period of 50 years is about 45 ms-1 (56 ms-1). The intensity of the expected extreme winds is closely related to orography. The study is based on wind and wind gust observations that were collected and quality controlled for the specific purposes herein. We also make use of a 12-year high-resolution regional simulation to provide simulation-based wind return level maps that endorse the observation-based results. Such an exhaustive methodological sensitivity analysis with a long high-resolution simulation over this region was lacking in the literature., Ministerio de Ciencia e Innovación (MICINN), Global Forecasters S.L., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

The land is a pivotal component of the Earth and its climate system since many processes of natural variations in the climate system, which affect the environment and human society, are governed by the land surface. Hence, a good representation of the thermal and hydrological states of the land surface in climate models is important to have a realistic simulation of the coupling between the atmosphere and the lito-biosphere. An influencing factor for improving the realism of the ground energy and water balance in climate models is the depth of the land zero-flux Bottom Boundary Condition Placement (BBCP). Despite recent improvements in modeling land surface processes in climate models, only limited attention has been directed toward the effect of the BBCP in Land Surface Models (LSMs) and its impact on the representation of terrestrial thermodynamics. Previous analytical and modeling studies suggest that the simulation of subsurface thermodynamics in current-generation climate models is not accurate due to the zero-heat-flux BBCP being imposed too close to the surface. An insufficiently deep land component in current-generation climate models compromises the simulation of the terrestrial thermal state and can influence land-atmosphere interactions. Further improvements in LSMs relate to the representation and sensitivity of coupling processes between the ground thermodynamic and hydrological regimes. As moisture is one of the main drivers of near-surface climate interactions, the hydro-thermodynamic coupling is crucial for studying the impacts of perturbations caused by human activity. Under climate change conditions, some areas and ecosystems are more vulnerable to a rapidly warming world than others...