The European CORDEX (EURO-CORDEX) initiative is a large voluntary effort that seeks to advance regional climate and Earth system science in Europe. As part of the World Climate Research Programme (WCRP)-Coordinated Regional Downscaling Experiment (CORDEX), it shares the broader goals of providing a model evaluation and climate projection framework and improving communication with both the General Circulation Model (GCM) and climate data user communities. EURO-CORDEX oversees the design and coordination of ongoing ensembles of regional climate projections of unprecedented size and resolution (0.11 • EUR-11 and 0.44 • EUR-44 domains). Additionally, the inclusion of empiricalstatistical downscaling allows investigation of much larger multi-model ensembles. These complementary approaches provide a foundation for scientific studies within the climate research community and others. The value of the EURO-CORDEX ensemble is shown via numerous peer-reviewed studies and its use in the development of climate services. Evaluations of the EUR-44 and EUR-11 ensembles also show the benefits of higher resolution. However, significant challenges remain. To further advance scientific understanding, two flagship pilot studies (FPS) were initiated. The first investigates local-regional phenomena at convection-permitting scales over central Europe and the Mediterranean in collaboration with the Med-CORDEX community. The second investigates the impacts of land cover changes on European climate across spatial and temporal scales. Over the coming years, the EURO-CORDEX community looks forward to closer collaboration with other communities, new advances, supporting international initiatives such as the IPCC reports, and continuing to provide the basis for research on regional climate impacts and adaptation in Europe.

Heat waves are among the most relevant extreme climatic events due to their effects on society, agriculture and environment. the aim of this work is to improve our understanding of heat waves over the Mediterranean basin during the 21 st century from an ensemble of Regional Climate Models (RCMs). focus has been placed on sensitivities to forcing global models, emissions scenarios and the RcM resolution, being the first work based on Euro-CORDEX simulations to fully analyze future heat waves in the Mediterranean. Heat wave features are studied with Warm Spell Duration Index (WSDI, duration) and Heat Wave Magnitude Index daily (HWMId, intensity). Results indicate a large increase by the end of the century in both intensity and length of heat waves from all emissions scenarios, global models, and regional models at any resolution. Exceptional heat waves observed early on the century could then become normal by the end of this period. Forcing global models and emissions scenarios play a major role. clear added value on spatial distribution and heat wave indices are obtained from global to regional models dynamical downscaling, related to the important coastal or orographic aspects widely present over the Mediterranean.

Understanding space-time features of wind speed is of high interest in meteorology and several applied sciences. Accurate wind speed measurements in combination with reliable gridded products, such as reanalyses, are needed to address the main characteristics of the wind field. Hourly 10 m wind speed from the European Centre for Medium-Range Weather Forecasts (ECMWF) latest reanalysis (ERA5) is compared with HadISD wind observations from 245 stations across Europe. Averaged ERA5 hourly data is able to reproduce the annual cycle of monthly wind speed in Europe. ERA5 presents slightly larger (shorter) monthly medians in winter (summer) than observations. ERA5 is compared against observations for each station using a frequency distribution-based score (score, from 0 to 1). Most of the stations exhibit hourly scores ranging from 0.8 to 0.9, indicating that ERA5 is able to reproduce the wind speed spectrum range, from light to strong relative frequencies, for any location over Europe. Ranges of mean values, variability, distribution function parameters and high or low wind thresholds frequencies are shown for this ensemble of European stations, allowing for an overall description of wind features. Generally, there is no clear relationship between scores and the variables analysed. The correlation and scores between ERA5 and HadISD is even further increased at longer time frequencies (6-24 hourly), together with centred rootmean-square error (RMSE) and standard deviation decreases. Hourly wind data from ERA5 reanalysis is, despite some shortcomings, valuable information to perform further detailed studies with a regular spatial and time wind distribution, from the climatological or renewable energy perspectives, for example.

In recent decades, trends in photovoltaic (PV) technology deployment have shown an overall increase across the world. Comprehensive knowledge of the solar resource and its future evolution is demanded by the energy sector. Solar resource and PV potential have been estimated in several studies using both the global climate model (GCM) and regional climate model (RCM), revealing a GCM-RCM discrepancy in the projected change over Europe. An increase in surface solar radiation (SSR) (and therefore in PV potential production) is projected by GCMs, whereas most RCM simulations project a decrease in SSR over Europe. In this work, we investigate the role of aerosol forcing in RCMs as a key explaining factor of this inconsistency. The results show that RCM simulations including evolving aerosols agree with GCMs in the sign and amplitude of the SSR change over Europe for mid-21st century projections (2021-2050 compared to 1971-2000 for representative concentration pathway climate change scenario RCP8.5). The opposite signal is projected by the rest of the RCMs. The amplitude of the changes likely depends on the RCM and on its aerosol forcing choice. In terms of PV potential, RCMs including evolving aerosols simulate an increase, especially in summer for Central and Eastern Europe, with maximum values reaching +10% in some cases. This study illustrates the key role of the often-neglected aerosol forcing evolution in RCMs. It also suggests that it is important to be very careful when using the multi-model Coordinated Regional Climate Downscaling Experiment (CORDEX) projections for solar radiation and related variables, and argues for the inclusion of aerosol forcing evolution in the next generation of CORDEX simulations.

No abstract