Meteorological Factors Related to Summertime Temperature Extremes in Regional Climate Models over Europe

We evaluate the capability of regional climate models (RCMs) to simulate spatial patterns of links between atmospheric circulation, land–atmosphere interactions and summertime high temperature extremes (TE) over Europe. Five RCMs from the EURO-CORDEX project driven by global climate models were examined and compared to the reference data (ERA-Interim reanalysis). TE were analysed as excesses above the 90% quantile of daily maximum temperature distribution in summer over the 1979–2005 period. The occurrence and magnitude of TE was related to anomalies in 850 hPa u- and w-wind components, net shortwave radiation, and evaporative fraction. The links vary between geographical regions. In Scandinavia and the British Isles, increases of net shortwave radiation during TE are largest. A decrease of zonal flow is linked to TE mainly over the Atlantic coast and Eastern Europe, while southerly advection is enhanced during TE nearly over the whole domain. Differences in increases of net shortwave radiation during TE were found between European regions and also among the RCMs. The largest within-ensemble variability is manifested in evaporative fraction which is linked to the magnitude of TE but its relationships to precipitation are often suspicious in the RCMs. Substantially low values of evaporative fraction were associated with improper simulation of westerly advection in some RCMs, suggesting a relatively strong coupling between individual meteorological variables and their biases in the RCMs.