Increasing daily precipitation extremes despite declining annual totals in southern Europe: a modeling study on the effects of Mediterranean Sea warming

Understanding the evolving patterns of intense rainfall in the Mediterranean under climate change is an urgent challenge. Focusing on southern Italy, a representative sub-region of the Mediterranean basin, we examine in detail the role of sea-atmosphere-orography interactions, particularly the impact of increasing sea surface temperatures (SSTs), in enhancing heavy precipitation despite overall drying. Twenty consecutive precipitation events, identified during a particularly intense rainy season (September–December 2019), are reproduced at convection-permitting resolution (2 km) using the Weather Research and Forecasting (WRF) model forced by ERA5 reanalysis boundary conditions. Two additional scenarios are then tested: one with past SST levels approximating those of 1980, and another with SST increases consistent with end-of-century Shared Socioeconomic Pathways (SSPs), such as SSP 3-7.0 and SSP 5-8.5. The WRF simulations accurately reproduce cyclone tracks and precipitation patterns, indicating that, with all other factors held constant, increased SSTs could boost the frequency of heavy rainfall over land by intensifying otherwise weaker events. However, for the most intense events analyzed, spatially averaged accumulated precipitation over land remains largely unchanged because the heaviest precipitation occurs over the sea. The study highlights the value of high-resolution, convection-permitting simulations for capturing complex processes in orographically challenging regions and helps shed light on the seemingly contradictory coexistence of increasing daily precipitation extremes and declining annual precipitation totals in Southern Europe.