Characteristics of extreme precipitation in the Vosges Mountains region (north-eastern France)

摘要

In this research, different characteristics (duration, affected area, extremity, and synoptic conditions) related to extreme precipitation events (EPEs), and the trends in frequency of EPEs in the Vosges Mountains (VG) region (north-eastern France) have been analysed and the events were evaluated on regional scale using the Weather Extremity Index. The index combines three aspects of an EPE - rarity, spatial extent, and duration - and it enables a quantitative comparison of these aspects in a data set of EPEs. In this study, 54 EPEs (which occurred during 1960-2013) were selected using daily precipitation totals from meteorological stations. Although possible maximum duration of an EPE was set to 10 days, all detected EPEs lasted 1-5 days. The prevailing short EPEs (1-2 days) affected smaller areas as compared to long EPEs (3-5 days). Instead of the winter maximum of mean precipitation in the VG, the autumn EPEs prevailed in the data set (40% of all EPEs including the four strongest EPEs). Using the manual and the automated catalogues (Grosswetterlagen and SynopVisGWL, respectively), majority of the 54 EPEs was found associated with the west cyclonic weather type; however, none of the five maximum events was produced by this weather type. The two strongest EPEs were related to the stationary cold front rather than to the expected strong zonal circulation. The EPEs were mostly related to strong southwest airflow and flux of specific humidity. No significant trend was found in frequency of EPEs during the 54 years. Our results highlight new insights into the extreme precipitation in VG region. We believe that the ranking of EPEs according to their extremity in the VG region provides useful information for local decision making authorities, engineers, and risk managers.