Historical (2005-2019) reconstruction of regional scale climate and atmospheric composition over Europe

The main objective of the Horizon Europe project FOCI (non-CO₂ Forcers and their Climate, Weather, Air Quality and Health Impacts) is to improve our knowledge of individual and cumulative contribution of non-CO₂ radiative forcers and their precursors on climate and air quality. Due to their short lifetime and their non-uniform emission footprint, the short-lived climate forcers (SLCF) are expected to have different impacts at regional scale. To describe and assess the impact of SLCF, we have developed a framework of coupling global climate model, EC-Earth3, to regional climate models (RCMs), to conduct historical simulations over Europe using CEDS SLCF emissions and LUCAS land cover to maintain consistency with CMIP6 simulations. During the first phase of the project RCMs, consisting of meteorological and chemical transport models WRF+CMAQ and WRF+FARM, have been applied over the CORDEX European domain for years 2005 -19 driven by ERA5 meteorological and CAMS global atmospheric composition reanalyses to provide an historical baseline simulation to be compared and verified versus observations and existing meteorological and tracers’ concentration reanalyses. The verification of the modelling systems performances reconstructing meteorological variables, pollutants’ concentration and their variability observed during the historical period is necessary to validate their planned downstream use to downscale EC-Earth3 CMIP6 simulations under the SSP3.7.0 and SSP3.7.0-lowNCTF scenarios. Meteorological variables compared positively with METAR observations at selected locations. Temperature increasing trend shows intensity and spatial features coherent with those depicted by existing analyses, with a limited negative bias on the annual mean values with respect to both analyses and selected stations (BIAS=-0.7 − +0.3 K; RMSE=1.6 − 2.2 K; correlation=0.97 − 0.98). Wind speed shows positive comparison with mixed bias values at selected airport locations (BIAS=-0.8 − +0.4 m/s; RMSE=1.2 − 2.1 m/s; correlation=0.48 − 0.80) similarly to relative humidity (BIAS=-5.3 − +6.4 %; RMSE=9 − 16 %; correlation=0.71 − 0.85). Precipitation fields have structure coherent with that of other analyses with increased resolution and different biases with respect to different analyses. Wind and precipitation show varying trends on different areas of the continent. Climate stressors trends will be compared too. Concentrations of the main pollutants show space distribution and values range similar to those shown by existing reanalyses (e.g. CAMS global and CAMS regional ensemble median). Local differences and biases are preliminary attributed to the significant differences of the emission inventories supporting RCMs simulations and existing analyses. Historical atmospheric composition simulations will be completed by early summer and a thorough comparison with observations and reanalyses will be presented at the meeting.