Past evolution of western Europe large-scale circulation and link to precipitation trend in the northern French Alps

Abstract. Detecting trends in regional large-scale circulation (LSC) is an important challenge as LSC a key driver of local weather conditions. In this work, we investigate the past evolution western Europe based on 500 hPa geopotential height fields from 20CRv2c (1851–2010), ERA20C (1900–2010) and ERA5 (1950–2010) reanalyses. We focus characteristics using three atmospheric descriptors that are analogy by comparing daily to each other. They characterize stationarity shape how well reproduced climatology. A non-analogy descriptor also employed account for intensity centers action. then combine four with existing pattern classification over period 1950–2019 study recent changes two main influences driving precipitation northern French Alps. correspond Atlantic dominated zonal flow Mediterranean low-pressure anomalies near Atlantic, close Portugal. Even though consistent among reanalyses after 1950, find major differences between 1900 1950 accordance previous studies. Notably, produces flatter shapes beginning 20th century shows reinforcement meridional pressure gradient not observed 20CRv2c. Over 1950–2019, show winter circulations (zonal flows) tend be shifted northward, they become more similar known circulations. stationary, associated stronger action autumn, while opposite behavior winter. Finally, discuss role these seasonal extreme linked (a) decreasing contribution (b) likely generate autumn.