Maines et al. (2026) 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

Identification

• Journal: Weather and Climate Extremes
• Year: 2026
• Date: 2026-02-28
• Authors: Elena Maines, Alice Crespi, Massimiliano Pittore, Marc Zebisch
• DOI: 10.1016/j.wace.2026.100880

Research Groups

• Center for Climate Change and Transformation, Eurac Research, Bolzano, Italy
• Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy

Short Summary

This study comprehensively assesses 1-day precipitation extremes in Trentino – South Tyrol (eastern Italian Alps) using observations (1956-2023) and climate model projections, finding increasing intensity and frequency in both past observations (especially in the north, summer/autumn) and future projections, with rarer events becoming more probable under higher warming levels.

Objective

• To provide a comprehensive assessment of observed trends (1956-2023) and projected changes under future global warming levels in the intensity, frequency, and spatial patterns of 1-day precipitation extremes in Trentino – South Tyrol (eastern Italian Alps) to inform risk management and adaptation.

Study Configuration

• Spatial Scale: Regional scale (Trentino – South Tyrol, approximately 13,000 km²), with climate model projections on a 0.11° x 0.11° (~12.5 km) grid, bias-adjusted and resampled to a 1 km grid. Point observations from 66 meteorological stations.
• Temporal Scale: Historical observations from 1956 to 2023 (68 years). Future climate projections extend until 2100, analyzed across different Global Warming Levels (GWLs) defined by 20-year (extended to 30 or 40 years for Regional Frequency Analysis) periods.

Methodology and Data

• Models used: EURO-CORDEX Regional Climate Models (RCMs) ensemble (17 simulations) under Representative Concentration Pathway 8.5 (RCP 8.5) scenario.
• Data sources:
  • Observational daily precipitation data from 66 meteorological stations in Trentino – South Tyrol, Switzerland, and Austria (1956-2023).
  • Gridded observational dataset for Trentino – South Tyrol (Crespi et al., 2021) for bias adjustment.
  • EURO-CORDEX RCM simulations (bias-adjusted).
  • HadCRUT5 dataset for Northern Hemisphere temperature anomalies.

Main Results

• Observed 1-day precipitation maxima (Rx1day) show an overall increasing tendency over 1956-2023, with significant positive trends (+4.8 % per decade relative to 1991-2020 average) mostly in the north-central part of South Tyrol, particularly in summer and autumn.
• Multidecadal oscillations are observed, with a more pronounced increase in Rx1day anomalies after 2000.
• Climate scaling suggests Rx1day generally increases with warming, especially in summer (+6.3 % °C⁻¹) and autumn (+8.4 % °C⁻¹), but shows negative scaling in winter.
• Based on observations, median 20-year return levels for Rx1day range from approximately 70 mm/day to 120 mm/day across the region, while 100-year return levels range from approximately 90 mm/day to 140 mm/day.
• Future projections indicate an increase in annual Rx1day intensity across the entire region under all GWLs, with ensemble median increases ranging from +3 % (GWL +1.5 °C) to +18 % (GWL +4 °C) relative to current conditions (GWL +1 °C).
• The greatest projected increases are in southern Trentino and eastern parts of the region, with the highest seasonal changes in autumn and winter (e.g., +15.2 % for autumn and +17.8 % for winter under GWL +4 °C).
• Projected return levels for Rx1day show increases becoming larger for rarer events and under warmer scenarios, with ensemble-median changes rising from +3 % to +11 % under GWL +1.5 °C to +17 % to +37 % under GWL +4 °C across return periods.
• The increase in return levels scales at approximately +7 % °C⁻¹ per degree of warming.
• The exceptional Vaia Storm (October 2018) 3-day precipitation event is estimated to be more probable today than in earlier decades, and its recurrence interval is projected to decrease by more than 50 % under the highest warming scenarios (GWL +4 °C) at most locations.

Contributions

• Provides a comprehensive regional assessment of 1-day precipitation extremes for Trentino – South Tyrol, combining long-term observations (1956-2023) and future climate model projections.
• Offers a consistent and seamless understanding of ongoing and future tendencies in precipitation extremes at a local level.
• Delivers a risk-oriented understanding by assessing changes in intensity, occurrence probability, and return levels of rare events, including a detailed case study of the Vaia Storm.
• Generates supporting information for local risk management and adaptation strategies by quantifying future changes in extreme precipitation characteristics.

Funding

• Interreg Alpine Space Program 2021-27, project number ASP0100101, “How to adapt to changing weather eXtremes and associated compound and cascading RISKs in the context of Climate Change” (X-RISK-CC).

Citation

@article{Maines2026Recent,
  author = {Maines, Elena and Crespi, Alice and Pittore, Massimiliano and Zebisch, Marc},
  title = {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},
  journal = {Weather and Climate Extremes},
  year = {2026},
  doi = {10.1016/j.wace.2026.100880},
  url = {https://doi.org/10.1016/j.wace.2026.100880}
}