Recent and future variability in 1-day precipitation extremes in Trentino – South Tyrol (Eastern Italian Alps) based on observations (1956-2023) and climate model projections

Abstract

Precipitation extremes are some of the most impactful events in mountain environments due to their triggering potential for hazards, such as gravitational mass movements and floods, damaging human settlements and economic activities. Intensifying extreme precipitation has been documented for the Alps and projected for the future decades, although with substantial spatial variability. Understanding ongoing and future changes in heavy precipitation characteristics on a regional scale is crucial for informing risk-oriented applications and supporting local adaptation. This study presents a comprehensive assessment of 1-day precipitation extremes in Trentino – South Tyrol (eastern Italian Alps), based on past observations and climate model projections. We analyze observed trends and variability in intensity over the period 1956-2023 and assess changes under future global warming levels. A regional frequency analysis adopting a data-pooling approach is applied to estimate current and future occurrence probabilities of 1-day precipitation extremes. Increasing intensity and frequency are observed, with significant trends mostly in the northern part of the region, especially for autumn, summer and on an annual level. However, the long-term signal reveals decadal variations and a more pronounced increase over recent years. Greater intensity and frequency are also projected for the future throughout the region with major changes for higher warming levels and rarer events. Precipitation events like the one recorded during the exceptional Vaia Storm (October 2018) turn out to be more probable today than in earlier decades, and their recurrence interval is projected to further decrease by more than 50 % under the highest warming scenarios.