Evaluation of Convection-Permitting Precipitation Simulations for the Study of Rainfall Erosivity in Sicily

Abstract

Recent European-scale studies highlight the susceptibility of the Italian territory to rainfall-induced soil erosion. As the climate warms, the water cycle is expected to intensify, leading to modifications in the rainfall patterns and to an increase in extreme precipitation events. Within this framework, climate models at convection-permitting resolutions have demonstrated to better represent intense precipitation at sub-daily durations than regional climate models. This enables a more accurate estimation of expected changes on those extremes. Our study aims to explore the capabilities of a convection-permitting model on providing rainfall data for a reliable estimation of rainfall erosivity. We rely on the climate model VHR-PRO_IT, available for over Italy and run by CMCC (Centro Euro-Mediterraneo sui Cambiamenti Climatici). We focus on the Sicily region, where an extensive dataset of rainfall erosivity is available, derived from estimation methods calibrated on erosivity measurements. The region represents an interesting study area due to the remarkable spatial variation in the rainfall regime and complex orography. We use data from 171 rain gauges evenly dis-tributed over Sicily as a benchmark. We investigate the capability of the climate model to simulate 2-yr return levels at 1 h, 6 h and 24 h duration, which provide the input for a rainfall erosivity model. The analysis highlights the impact of rain-fall duration and elevation on the climate model accuracy, with generally higher underestimation of return levels at short duration and in lowlands. These results provide indications for the development of bias adjustment on simulated return levels, in order to have reliable estimation of rainfall erosivity from the climate model. This preliminary application, centered on Sicily, sets the stage for potential extensions on entire Italy and on future climate scenarios.