Understanding the observed changes in High-Impact Precipitation Events across the European Alps

The magnificent but complex topography of the Alps makes them Europe's indispensable water tower, channeling vital precipitation into rivers that sustain communities, economies, and ecosystems downstream. Therefore, gaining an understanding of how precipitation behaves in this mountain region is crucial. These mountain regions are home to a great variety of climatic regimes, from Mediterranean and Atlantic maritime to strongly continental, and yet, hydro-meteorological extremes pose an increasingly disastrous threat, heightening pressure on water security, infrastructure resilience, and transboundary risk management.

There has been much research into precipitation extremes that has taken place over various parts of the Alps, bringing to light their intensity, frequency, and dynamics. However, these studies are confined to specific regions of the mountain range. The novelty of this work is threefold: a) It is based on a consistent, high-resolution, observation-based, recently published alpine-wide database of High-Impact Precipitation Events (HIPEs), observed for the period 1961-2022 and developed through a homogeneous transnational approach (Lemus-Canovas et al., 2025); b) It is based on a multi-metric analysis to draw a comprehensive picture of changes in the HIPE features, including the assessment of their spatial extent, which has not been addressed before; and c) The variations in the different characteristics of these events, as well as the responsible drivers, are addressed by considering the contribution of the annual frequency of weather types.

By combining Regression Analysis with the modeling of the Generalized Extreme Value distribution, the study was able to identify significant patterns of increase in HIPE occurrences in subregions of the Alps, along with different contributions from the main weather types when explaining the annual variability of the different characteristics of HIPEs. Such techniques offer a nuanced view of the contribution of atmospheric dynamics and local factors in determining the observed variability of precipitation extremes.

Overall, our results indicate that the emerging shifts in HIPE behavior will most likely result from a nonlinear interaction of thermodynamic intensification and dynamics of circulation. The findings are intended to emphasize the emerging regional vulnerabilities and provide science-based support for cross-border preparedness for flooding and adaptation to climate change in Alpine environments.

Keywords: High-Impact Precipitation Events (HIPEs), European Alps, trend analysis, Alpine-wide observations

Reference: Lemus-Canovas, M. (2025). High-Impact Precipitation Events in the European Alps (1961–2022) [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.17047822