Land–Sea Distribution of Ground Precipitation in Mediterranean Storms

Abstract

The Mediterranean basin is traditionally a hotspot where copious amounts of water vapor at low- and mid-tropospheric levels often favor atmospheric instability and the deepening of storms, leading to intense rainfall events with consequent flash floods. Moreover, this region includes sharp land–sea transitions, narrow maritime areas, and mountain chains which enhance convective precipitation. In this study, radar precipitation data were used to investigate the spatial distribution of rainfall swaths for seven severe cyclones originating over the Mediterranean Sea which produced intense flash inundation events along the western coast of Italy in the last decade (2011–2020). Based on 5 min precipitation amounts gridded at a 1 km spatial resolution, the temporal evolution of these storms displays a curvilinear path moving from sea to inland. Results show that more than half of the total precipitation for the analyzed events occurred on sea, and the total amount of storm rainfall over the marine surface exceeded that over land in four events out of the seven. Since the coastline strongly affects the rainfall pattern, we analyzed the land–sea discontinuity, which is a key factor controlling the spatial distribution of storm rates through their trajectory, where a small shift in precipitation target might smooth ground effects and mitigate flood impacts.