Large-scale synoptic types and their impact on European precipitation

Atmospheric circulation strongly modulates precipitation patterns throughout Europe. A selection of synoptic types was chosen to investigate the impact of circulation on the spatial distribution of precipitation within Europe and neighbouring regions (for 1951-2010). Applied were (1) the original and one automated version of the Grosswetterlagen classification, (2) the Vangengeim-Girs classification and (3) a dataset of the North Atlantic Oscillation (NAO). Daily values of the E-OBS gridded precipitation dataset were allocated to synoptic types, visualising precipitation anomalies (in percent) during winter (October-March) and summer (April-September) half years. Anomalies from average precipitation conditions (only) contain days connected to each of the investigated synoptic types. Distinct anomaly patterns become visible and are explained by the location of pressure systems. Patterns are spatially similar between both half years for Grosswetterlagen and Vangengeim-Girs classifications, while the NAO shows pronounced seasonal changes. Precipitation anomaly maps were applied to help explain observed changes in European precipitation amounts from 1981 to 2010, as compared to 1951-1980. Changes of precipitation amounts were related to frequency changes of synoptic types, predominantly during the winter half year. Here, increasing (decreasing) frequencies of synoptic types connected to westerly (easterly) inflow supported higher precipitation amounts in northern Europe and lower amounts in southern Europe.