Dynamical Factors Heavily Modulate the Future Increase of Sub-Daily Extreme Precipitation in the Alpine-Mediterranean Region

Abstract

Quantifying the future probability of sub-daily extreme precipitation in a changing climate is crucial for risk management, engineering, and insurance. Kilometer-scale convection-permitting climate models (CPMs) represent convective precipitation and complex terrain more realistically than other climate models, thereby enhancing the representation of sub-daily extremes. This study employs a novel statistical approach to evaluate projected changes in extreme sub-daily precipitation and provides a physical interpretation of their driving processes. It focuses on the complex-topography area of northern Italy, where resides almost half of the Italian population and a significant portion of the Italian economy, with a rich diversity in industry, agriculture, tourism. We use precipitation data from a CPMs ensemble covering three periods: historical (1996–2005), near future (2041–2050), far future (2090–2099) under the RCP8.5 scenario. Sub-daily to daily precipitation extremes with return periods up to 100 years are examined. We find a general intensification of extremes across all durations (from 1 to 24 hr), stronger at shorter durations and rarer probabilities. Spatial patterns vary with duration, with higher and significant increases emerging in mountainous areas in Eastern Alps and North Apennines. The detected changes cannot be explained by thermodynamics alone, highlighting the modulating role of the changes in atmospheric dynamics. These findings are crucial for enhancing risk management strategies and adapting to natural hazards in a warming climate. This approach may be exploited in larger scale analysis.