Will Future Southwestern Europe Large‐Scale Circulations Resemble Past Circulations? A Focus on the Circulations Driving Extreme Precipitation in the Northern French Alps

Abstract

AbstractDetecting trends in regional large‐scale circulation (LSC) is an important challenge as LSC is a key driver of local weather conditions. In this work, we focus on two LSC characteristics that are linked to the generation of extreme precipitation in the northern French Alps and that allow interpreting changes in flow direction and flow intensity. Considering 500 hPa geopotential height fields, we show that CNRM‐CM6‐1 climate model simulates that future circulations (2015–2100) will tend to feature stronger flows with more marked westerly component. They will visit up to 30% more often the atmospheric states that are characteristic of extreme precipitation in the northern French Alps with particularly over‐recurrence in winter (+60%) and spring (+50%). In a “fictive” world where only these characteristics would change, this would induce an overall over‐recurrence of extreme precipitation of up to 15% (30% in winter), which corresponds to about 20% of the change in extreme precipitation simulated directly by CNRM‐CM6‐1. Applying the present methodology to an ensemble of climate models appears as the next step to account for simulation uncertainties both in LSC and precipitation extremes.