Influence of submonthly air-sea coupling on heavy precipitation events in the Western Mediterranean basin
Berthou, Ségolène ; Mailler, Sylvain ; Drobinski, Philippe ; Arsouze, Thomas ; Bastin, Sophie ; Béranger, Karine ; Flaounas, Emmanouil ; Lebeaupin Brossier, Cindy ; Somot, Samuel ; Stéfanon, Marc
Heavy precipitation events (HPEs) can be a major cause of damage and casualties in the Mediterranean basin. With the use of atmosphere-ocean coupled regional climate models (AORCMs) and the advantage of 24 years of simulation (1989-2012), we identified regions with potential impact of submonthly air-sea coupling on HPEs among the regions hit by heavy rain during HyMeX 1st special observation period (SOP1): Valencia in Spain, the Cévennes in Southern France, Liguria in Northwestern Italy, Calabria in Southern Italy and Northeastern Italy. A first evaluation of the two AORCMs (MORCE and CNRM-RCSM4) against gridded precipitation datasets showed that 70 to 90% of the 30 most intense HPEs simulated were observed HPEs for most regions. The Cévennes, Valencia and Calabria were the only three regions to show a statistical relationship between rain differences and SST differences where the low-level jets that feed the events most frequently blow. This sensitivity of precipitation to SST changes is due to low-level wind changes related with changes in surface heat fluxes. Based on the calculation of submonthly variations in these regions during HyMeX, HPEs on the 28/09/2012 and 12/10/2012 in Valencia and on 25-26/10/2012 in the Cévennes have most probably been affected by submonthly air-sea coupling.
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