6. Workshop Alpine Hydrologie

High-resolution climate projections indicate that the Eastern Alps will be among the regions most strongly affected by the intensification of sub-daily extreme precipitation during the twenty-first century. Using an ensemble of convection-permitting climate models (CPMs) with approximately 3-km resolution and the Simplified Metastatistical Extreme Value (SMEV) framework, the study shows that extreme precipitation events are expected to become both more frequent and more intense, with the largest increases occurring for short durations (1–6 hours) and for the rarest events.

Particular attention is devoted to the mountainous sector of the Eastern Alps influenced by both westerly weather systems and moisture transport from the Adriatic Sea. In this area, projected end-of-century changes under the RCP8.5 scenario reach 35–40% increases for hourly precipitation extremes, while substantial increases remain evident at longer durations. The amplification is even stronger for 100-year return levels than for 20-year return levels, indicating that the most severe events are expected to experience the largest relative increases.

A key finding of the study is that these projected changes cannot be explained solely by thermodynamic effects associated with a warmer atmosphere and increased moisture availability. In particular, the observed increases exceed what would be expected from the Clausius–Clapeyron scaling, which predicts an increase in atmospheric moisture-holding capacity of about 7% per degree Celsius of warming. Analysis of the statistical properties of precipitation extremes reveals a progressive increase in the heaviness of the distribution tails, suggesting that changes in atmospheric dynamics play a major role in shaping future extremes. Modifications in large-scale circulation patterns, moisture convergence, and seasonality of intense precipitation substantially amplify extreme precipitation beyond the increase attributable to Clausius–Clapeyron thermodynamic scaling alone

These results identify the Eastern Alps as a regional hotspot of future precipitation intensification and highlight the need to account for both thermodynamic and dynamical drivers when assessing future flood risk, infrastructure resilience, and climate adaptation strategies in mountain environments.