Flood discharge in Europe influenced by atmospheric blocking

Floods are among the most disastrous and costly extreme weather events in Europe. Atmospheric blocking patterns (persistent and self-preserved weather systems that propagate very slowly and slow down the large-scale circulation) are part of the main weather regimes in the Euro-Atlantic region and play a central role in shaping the extreme weather of Europe and its impacts on the surface. Nevertheless its socioeconomic importance, the covariability between atmospheric blocking and river flood has rarely been examined on the climate and continental scales. Our study explores the hydrological way that atmospheric blocking propagates into floods and how this relationship varies over space and time, in >6000 basins of Europe during the last 60 years. We analyse flood discharge observations from a pancontinental database and atmospheric and terrestrial variables derived from reanalysis. Our results show clear relationships between flood characteristics and atmospheric blocking occurring in upstream to downstream relative positions. Our analyses highlight that atmospheric blocking significantly influences spatial and temporal variability of flood discharge in Europe, being this relationship modulated by regional hydrological characteristics and the interaction between soil and rainfall. These findings provide a framework to understand the regional impacts of atmospheric blocking over floods and point towards near-climate sources of predictability for floods in Europe.