Evaluation and projected changes in rainfall erosivity: Topography dependence revealed by Convection-Permitting climate projections for the Mediterranean island of Sicily

Abstract

Recent studies across Europe highlight the vulnerability of Mediterranean countries to rainfall-induced soil erosion. Climate change is intensifying the water cycle, leading to shifts in rainfall patterns and more frequent extreme precipitation events. Convection-permitting climate models (CPMs) outperform regional models in capturing intense sub-daily rainfall, providing more accurate projections of future extreme events. This study exploits a simplified rainfall erosivity model which uses 2-yr sub-daily rainfall quantiles as input to: investigate the ability of a CPM to provide reliable rainfall data for assessing rainfall erosivity; analyze the projected changes in rainfall quantiles and rainfall erosivity. The study is carried out in Sicily, which offers an ideal case study given its rainfall variability and complex topography. Data from 171 rain gauges are used to evaluate the CPM in simulating 2-year sub-daily rainfall quantiles and rainfall erosivity. Future changes are evaluated from the CPMs projections under the RCP8.5 scenario up to 2070.

The results show that model accuracy varies by rainfall duration and elevation, with greater underestimation of rainfall at shorter durations (up to −38 % on average at 1 h duration) and in coastal lowlands. Projections suggest an increase in intense rainfall, particularly for shorter durations, leading to higher rainfall erosivity (about + 20 % on average in the future). These findings underscore the need for bias adjustments in simulated rainfall data, considering both temporal scales and topographic influences. The study also highlights the potential for increased rainfall erosivity under climate warming, stressing the importance of developing soil conservation strategies and policies to address future challenges. This research set the stage for wider-area applications.