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The RegCM climate model was used at a 35 km resolution to downscale the 3-member global ECHAM5/MPI-OM ensemble based on the IPCC A2 scenario covering the EuropeanMediterranean domain. Within the reference climate (1961−1990), the model high 2 m temperatures (T2m) were reduced and low temperatures were increased relative to verification in a large portion of the domain. Precipitation was underestimated in summer over the Mediterranean region but was overestimated over western Europe in winter, probably due to excessive westerlies in the global model. When RegCM was forced by ERA-40, the dominant errors in the summer T2m appear to be genuine RegCM errors, but a large fraction of errors in winter precipitation was imported from the lateral boundaries. In the near future (2011−2040), the summer T2m is projected to increase by +1.8°C over southwest Europe. The simulated change in precipitation is small and is significant only in regions around the Mediterranean. The wetter north and drier south, a major feature in projections of the European winter climate in the late 21st century, is not predicted for the near future. Similarly, summer drying is confined to western Europe in contrast to nearly continental scale drying observed in projections of the late 21st century. This finding may influence the approaches for adaptation to climate change in the first half and at the end of this century. The effects of downscaling at small scales are analysed for the case of Croatia. The spatial distribution of the number of days with extreme T2m and precipitation in RegCM is consistent with observations. However, this metric is generally underestimated, indicating that over complex orography, even higher horizontal resolution is needed to better resolve climate extremes.

Five indices of extreme precipitation are analysed over the Croatian Adriatic region on a seasonal and annual basis from 19 meteorological stations and a 3-member ensemble of the Regional Climate Model (RegCM3) simulations in the reference (1961−1990) and the near-future (2011−2040) climate. Future climate integrations are performed under the IPCC A2 emission scenario. Uncertainty of projected changes is assessed by comparing RegCM3 results with those from a subset of the ENSEMBLES regional climate models. Observed wet extremes exhibit large values in the areas close to the coastal mountains. Interannual variability in the number of very wet days (R95) and the fraction of precipitation associated with very wet days (R95T) is relatively large in all seasons, indicating a variable synoptic activity over the Adriatic region from one year to the next, as well as variable intense showers in the summer. The most prominent feature is a statistically significant decrease in the observed maximum number of consecutive dry days (CDD) during the autumn. When compared against the observations, RegCM3 overestimates observed precipitation and maximum 5 d precipitation amounts (Rx5d) in all seasons except the summer with statistically significant differences. Simulated number of dry days (DD) is generally underestimated and, consequently, R95 is mostly overestimated. Of all indices considered, R95T is best simulated by the model. The interannual variability of precipitation and indices is generally well reproduced. The projected changes in the mean and indices of extreme precipitation in the near future are weak overall, except in the autumn, in both the RegCM3 ensemble and selected ENSEMBLES models. Although the Mediterranean region is characterised as one of the regions most responsive to climate change, our results indicate that over the eastern Adriatic region, significant changes may not occur in the near future.

Various measures of forecast quality are analyzed for 2-m temperature seasonal forecasts over Europe from global and regional model ensembles for winter and summer seasons during the period 1991 to 2001. The 50-km Regional Climate Model (RegCM3) is used to dynamically downscale nine-member ensembles of ECMWF global experimental seasonal forecasts. Three sets of RegCM3 experiments with different soil moisture initializations are performed: the RegCM3 default initial soil moisture, initial soil moisture taken from ECMWF seasonal forecasts, and initial soil moisture obtained from RegCM3 ECMWF interim ReAnalysis (ERA-Interim)-driven integrations (RegCM3 climatology). Both deterministic and probabilistic skill metrics are estimated.The better-resolved spatial scales in near-surface temperature by RegCM3 do not necessarily lead to the improved regional model skill in the regions where systematic errors are large. The impact of initial soil moisture on RegCM3 forecast skill is seen in summer in the southern part of the integration domain. When regional model soil moisture was initialized from ECMWF seasonal forecasts, systematic errors were reduced and deterministic skill was enhanced relative to the other RegCM3 experiments. The Brier skill score for rare cold anomalies in this experiment is comparable to that of the global model, whereas in other experiments it is significantly smaller than in global model.There is no major impact of soil moisture initialization on forecast skill in winter. However, some significant improvements in RegCM3 probabilistic skill scores for positive anomalies in winter are found in the central part of the domain where RegCM3 systematic errors are smaller than in global model.

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