Bridging Regional Hydroclimatic Extremes and Atmospheric Blocking: A German Case Study

Germany has experienced an increasing number of hydroclimatic extreme (HCE) events in recent decades. Heavy rainfall, dry spells, heatwaves, and (flash) droughts have intensified in both frequency and severity under ongoing climate change. However, the definition and monitoring of HCEs remain largely based on near-surface variables (e.g. precipitation, potential evapotranspiration, 2 m air temperature, and soil moisture), while their links to large-scale atmospheric dynamics and synoptic systems are still not well understood.

In this study, we map the occurrence and trends of multiple HCE types prevalent in Germany, investigate their co-occurrence, and assess their teleconnections with atmospheric blocking patterns. We use downscaled, gridded (1 × 1 km), daily data from the German Weather Service for the period 1970–2025 for precipitation, temperature, air humidity, and solar radiation to characterise the occurrence and trends of heavy rainfall, dry spells, heatwaves, and flash droughts. In addition, we use ERA5 reanalysis data to compute the Standardised Precipitation–Evapotranspiration Index (SPEI) and to assess drought occurrence and trends across Germany. ERA5 fields are also employed to identify blocking events following Detring et al. (2021).

Preliminary results indicate positive trends in the occurrence of dry spells, heatwaves, and flash droughts, particularly in southern Germany, and reveal strong links between droughts and Omega blocking, exemplified by the 2022 drought event.