Connecting Drought Events with Atmospheric Circulation Patterns in Western Central Europe: A Historical Perspective

Droughts in Western Central Europe (WCE) have recently attracted attention due to their detrimental impact on crops, ecosystems, and society, as evidenced by events in 2018 and 2022. In this region, however, their variability and underlying causes remain unclear. This study aims to associate droughts with the atmospheric circulation to gain insight into their drivers. We employed reanalysis datasets (ERA5, 20CRv3, and ModE-RA) to identify meteorological drought events using the Standardized Precipitation Evapotranspiration Index at a 3-month scale and consistently connect them to atmospheric circulation patterns through k-means clustering. The three datasets are evaluated over the WCE regions, showing that they are highly reliable over periods ranging from 70 to 180 years, providing a long perspective on the recent events. Firstly, we demonstrate that droughts in WCE display a strong multidecadal variability with no significant long-term trend. Although precipitation has increased over time, this has been offset by the rising atmospheric evaporative demand due to warming. Secondly, we identify three distinct atmospheric circulation patterns associated with drought events in WCE: a high-anomaly geopotential height centred over Western Central Europe (WCE+); a dipole of high-anomaly geopotential height over the British Isles and low-anomaly geopotential height over the Maghreb (BIM+); and the negative phase of the North Atlantic Oscillation (NAO-), predominantly in winter. Our analysis shows that droughts have become increasingly associated with WCE+ over the last century, while their association with NAO- has decreased over the past 180 years. This research provides a regional historical analysis of meteorological drought and its drivers, offering better insight into long-term regional climate change.