Linking European droughts to year-round weather regimes

Droughts are extreme events with major economic, social and environmental impacts, and it is crucial to be able to anticipate them.  To improve their prediction on a seasonal timescale, it is essential to better understand the underlying conditions that precede them. In  Europe, intra-seasonal to seasonal climatic variations are linked to atmospheric circulation and are weakly constrained by tropical teleconnections.

This study employs year-round weather regimes to demonstrate that the North Atlantic atmospheric circulation plays a fundamental role in precipitation deficits across Europe. Precipitation deficits are quantified using the reanalysed 3-month standardised precipitation index (SPI3). We use the SPI3 to define drought events and propose a new regionalisation of Europe, divided into regions with the same drought-related characteristics. We demonstrate that each weather regime is associated with a distinct precipitation pattern across regions, that remains relatively stable throughout the year. The representation of the regime-drought relationship in CMIP6 model simulations is then discussed.