Attribution of European precipitation and temperature trends to changes in synoptic circulation

Abstract. Surface climate in Europe is changing and patterns in trends have been found to vary at sub-seasonal scales. This study aims to contribute to a better understanding of these changes across space and time by analysing to what degree observed climatic trends can be attributed to changes in synoptic atmospheric circulation. The relative importance of synoptic circulation changes (i.e. trends in synoptic type frequencies) as opposed to trends in the hydrothermal prop-erties of synoptic types (within-type trends) on precipitation and temperature trends in Europe is assessed on a monthly basis. The study is based on mapping spatial and temporal trend patterns and their variability at a relatively high res-olution (0.5◦ × 0.5◦; monthly) across Europe. Gridded pre-cipitation and temperature data (1963–2001) originate from the Watch Forcing Data set and synoptic types are define