Assessment of the synoptic forcing associated with extreme precipitation events over Southeastern South America as depicted by RCMs at convective permitting resolution performed within a CORDEX FPS

SOLMAN, S.; FEIJOÓ, M.; LAVIN GULLON, A; FERNANDEZ, JESUS; PORFIRIO DA ROCHA, R; LLOPART, M.; CHOU, S; BETTOLLI MARIA LAURA; DOYLE, M; COPPOLA, E; GUTIERREZ LLORENTE, JM

Beijing

Conferencia; ICRC-CORDEX 2019; 2019

CORDEX

Southeastern South America (SESA) is one of the regions of the world where the deepest and mostintense convective storms develop. Initiated over the lee side of the Andes, these storms propagatefurther eastward as they grow up to the mature stage into mesoscale convective systems, fed bymoisture provided by a strengthened South American Low Level Jet, the development of a low levelpressure on the lee side of the Andes and a mid-level trough. In the context of the ongoing FlagshipPilot Study endorsed by CORDEX focused on extreme precipitation events over SESA, a series of RCM(regional climate model) simulations at convective permitting resolution (4 km) has been produced.The aim of this study is to assess the capability of these simulations in capturing the synoptic forcingassociated with the occurrence of extreme precipitation events over SESA. For that purpose, threeindividual storms of extreme characteristics were selected during the spring to summer season 2009-2010. Simulations were driven by the ERA-Interim reanalyses at two resolutions: 20 km and 4km. Twotypes of simulations were performed: the ?weather mode?, based on 72-hours simulations of theindividual cases, and the ?climate mode?, based on 6- months-length simulations for the period fromOctober 2009 to March 2010. The RCMs included in this first assessment are: RegCM4 (Univ. of SaoPaulo -Brazil), WRF3.8 (Univ. of Cantabria- Spain) and WRF3.9 (Univ. of Buenos Aires/CIMA-Argentina).The comparison among the convective permitting and parameterized convection simulations in termsof the triggering mechanisms associated with the extreme precipitation events is discussed. It wasfound that one of the largest differences among the two groups of simulations is in the low- levelmoisture flux convergence field, suggesting that the low-level wind and moisture fields are affected bythe occurrence of convection and they are sensitive to how convection is captured in the models.