Mediterranean Extreme Precipitation: Amplification by Warmer Sea Surface Temperatures in a Kilometer-Scale Regional Model
Résumé
We employ convection-permitting regional climate modeling to analyze the intense Mediterranean Heavy Precipitation Event (HPE) in October 2020 in the southeastern French Alps and northwestern Italian Alps regions, post passage of extra-tropical storm Alex. Exploring the event's sensitivity to warmer sea surface temperatures (SSTs), we conduct modeling experiments for September-October 2020 in western Europe. An ensemble-based approach is adopted to comprehensively assess local uncertainties purely driven by internal variability. Using the CNRM-AROME model, we accurately reproduce the HPE and precursor storm Alex characteristics, including the observed sequence of extreme events and related regional to local impacts. Sensitivity experiments are then conducted with idealized and uniform 2K warming and cooling patterns added to the SSTs over the entire domain and the Mediterranean Sea solely, all other forcings kept identical and representative of the 2020 observed conditions. SST warming intensifies the HPE's extremeness and accumulated precipitation amounts over the Alps. This is accompanied by a shift of the most intense precipitation eastward. In contrast, the strengthening of storm Alex with SST warming has limited impact on the Mediterranean HPE. Our findings underscore the crucial role of Mediterranean warming, enhancing moisture and instability upstream, and fostering deep atmospheric convection over the mountainous coastal region. A plausible worst-case scenario testing warmer SSTs in 2022 on HPE and storm Alex suggests milder precipitation-related impacts in the French Alpes-Maritimes region but increased damage in Italy.
Mots clés
Heavy precipitation events intensification of extreme precipitation sensitivity to sea surface temperature kilometer-scale regional climate modeling convection-permitting modeling
Heavy precipitation events
intensification of extreme precipitation
sensitivity to sea surface temperature
kilometer-scale regional climate modeling
convection-permitting modeling
Domaines
Océan, Atmosphère
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