Abstract. In the current work we present six hindcast WRF (Weather Research and Forecasting model) simulations for the EURO-CORDEX (European Coordinated Regional Climate Downscaling Experiment) domain with different configurations in microphysics, convection and radiation for the time period 1990–2008. All regional model simulations are forced by the ERA-Interim reanalysis and have the same spatial resolution (0.44°). These simulations are evaluated for surface temperature, precipitation, short- and longwave downward radiation at the surface and total cloud cover. The analysis of the WRF ensemble indicates systematic temperature and precipitation biases, which are linked to different physical mechanisms in the summer and winter seasons. Overestimation of total cloud cover and underestimation of downward shortwave radiation at the surface, mostly linked to the Grell–Devenyi convection and CAM (Community Atmosphere Model) radiation schemes, intensifies the negative bias in summer temperatures over northern Europe (max −2.5 °C). Conversely, a strong positive bias in downward shortwave radiation in summer over central (40–60%) and southern Europe mitigates the systematic cold bias over these regions, signifying a typical case of error compensation. Maximum winter cold biases are over northeastern Europe (−2.8 °C); this location suggests that land–atmosphere rather than cloud–radiation interactions are to blame. Precipitation is overestimated in summer by all model configurations, especially the higher quantiles which are associated with summertime deep cumulus convection. The largest precipitation biases are produced by the Kain–Fritsch convection scheme over the Mediterranean. Precipitation biases in winter are lower than those for summer in all model configurations (15–30%). The results of this study indicate the importance of evaluating not only the basic climatic parameters of interest for climate change applications (temperature and precipitation), but also other components of the energy and water cycle, in order to identify the sources of systematic biases, possible compensatory or masking mechanisms and suggest pathways for model improvement.

[1] Regional climate-air quality simulations were performed over Europe for two future decades, 2041-2050 and 2091-2100 under IPCC A1B scenario and the control decade 1991-2000. The simulations serve as a theoretical experiment investigating the impact of changing climate on summer surface ozone. Our simulations suggest that changes in summer surface ozone imposed by climate change until the 2040s are below 1 ppbv and more pronounced until the 2090s. The median of summer near surface temperature for whole Europe is 2.7 K higher at the end of the 21st century than to the end of the 20th century with more intense temperature increase simulated for southern Europe. A prominent feature is the decrease of cloudiness mostly over western Europe at the end of the 21st century associated with an anticyclonic anomaly which favors more stagnant conditions and weakening of the westerly winds for the larger part Europe southern of 50°N. Biogenic emissions double in the simulation at the end of the 21st century for latitudes below 50°and together with changes in circulation patterns, temperature, and solar radiation, contribute to the enhanced average ozone concentrations at the end of the 21st century. The change is more intense over southwest Europe, where the median of ozone increases by 6.2 ppbv. Sensitivity simulations suggest that biogenic emissions, temperature and solar radiation have a comparable impact on average surface ozone in the examined range of perturbations. The maximum response of the imposed perturbations was seen over southern Europe.Citation: Katragkou, E., P. Zanis, I. Kioutsioukis, I. Tegoulias, D. Melas, B. C. Krüger, and E. Coppola (2011), Future climate change impacts on summer surface ozone from regional climate-air quality simulations over Europe,

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Abstract. In the current work we present six hindcast Weather Research and Forecasting (WRF) simulations for the EURO-CORDEX domain with different configurations in microphysics, convection and radiation for the time period 1990–2008. All regional model simulations are forced by the ERA-Interim reanalysis and have the same spatial resolution (0.44°). These simulations are evaluated for surface temperature, precipitation, short- and longwave downward radiation at the surface and total cloud cover. The analysis of the WRF ensemble indicates systematic biases in both temperature and precipitation linked to different physical mechanisms for the summer and winter season. Overestimation of total cloud cover and underestimation of downward shortwave radiation at the surface, mostly when using Grell–Devenyi convection and the CAM radiation scheme, intensifies the negative summer temperature bias in northern Europe (max −2.5 °C). Conversely, a strong positive downward shortwave summer bias in central (40–60%) and southern Europe mitigates the systematic cold bias in WRF over these regions, signifying a typical case of error compensation. Maximum winter cold bias is over north-eastern Europe (−2.8 °C); this location is indicative of land–atmosphere rather than cloud-radiation interactions. Precipitation is systematically overestimated in summer by all model configurations, especially the higher quantiles, which are associated with summertime deep cumulus convection. The Kain–Fritsch convection scheme produces the larger summertime precipitation biases over the Mediterranean. Winter precipitation is reproduced with lower biases by all model configurations (15–30%). The results of this study indicate the importance of evaluating not only the basic climatic parameters of interest for climate change applications (temperature-precipitation), but also other components of the energy and water cycle, in order to identify the sources of systematic biases, possible compensatory or masking mechanisms and suggest methodologies for model improvement.

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