Soil moisture-atmosphere coupling strength over Central Europe in the recent warming climate

Abstract. In the last decades, Europe more often experiences periods of severe drought and heatwaves which have a major impact on agriculture and society. While land surface conditions were found to be crucial for exacerbating duration and intensity of these events, their influence is typically quantified for climate periods or single events. To provide an overview of how surface conditions shape land-atmosphere (LA) coupling, this study investigates interannual variability of LA coupling strength for the summer seasons 1991–2022 over Europe. The focus is set on the warm summers and the analysis is based on ERA5.

Especially the drought summer seasons 2003, 2018, and 2022 can be identified by the changing soil moisture-atmosphere coupling pattern in turn leading to an increased lifted condensation level height inhibiting local deep convection triggering. Summer 2021 was a special case as spring precipitation was on average and a heavy rain event occurred during July, resulting in high moisture availability leading to a change in the LA feedback strength. During the four warm and wet summers since 1991 no strong soil moisture-atmosphere coupling is observed as there is always enough soil moisture available for evaporation. The results obtained with respect to LA coupling strength reflect a shift in the coupling relationships toward reinforced heating and drying by the land surface under heatwave and drought conditions, whose frequency is increasing with ongoing climate change.