Atmospheric conditions favouring extreme precipitation and flash floods in temperate regions of Europe

Abstract. In recent years, flash floods have repeatedly occurred in temperate regions of central western Europe. Unlike Mediterranean catchments, this flooding behaviour is unusual. the past (especially 1990s), been characterized by predictable, slowly rising water levels during winter and driven westerly atmospheric fluxes. Here, we explore potential links causes between occurrence Europe to extreme precipitation specific conditions. We hypothesize that a change conditions has led more frequent events subsequently triggered flood To test hypothesis, compiled data on selected above 40 mm h−1 from radar (the RADOLAN “Radar-Online-Adjustment” dataset German Weather Service). Moreover, identified proxy parameters representative favouring ERA5 reanalysis dataset. High humidity (q) lower troposphere (q≥0.004 kg kg−1), sufficient latent instability (convective available energy (CAPE) ≥ 327 J weak wind speeds 10 m a.g.l. 500 hPa (WS10m-500hPa≤6 s−1) proved be characteristic intense rainfall can potentially trigger floods. relied linear models analyse years worth (1981–2020) as well related events. found significant increases moisture content instability. Parameters representing motion organization convective systems remained largely unchanged considered period (1981–2020); however, number events, their maximum 5 min intensities, hourly sums were large interannual variations, no trends could 2002 2020. Our study shows there single mechanistic path leading The interactions processes involved are so intricate analyses which consider other relevant factors, such intra-annual patterns or catchment-specific parameters, required.