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

SILVINA A SOLMAN; FEIJOO MARTIN; ALVARO LAVIN-GULLON; JESUS FERNANDEZ; ROSMERI PORFIRIO DA ROCHA; MARTA LLOPART; SIN CHAN CHOU; MARIA LAURA BETTOLLI; MOIRA DOYLE; ERIKA COPPOLA; JOSE MANUEL GUTIERREZ

BEIJING

Conferencia; INTERNATIONAL CONFERENCE ON REGIONAL CLIMATE ICRC2019-CORDEX ABSTRACT BOOK; 2019

WORLD CLIMATE RESEARCH PROGRAMME

Southeastern South America (SESA) is one of the regions of the world where the deepest and most intense convective storms develop. Initiated over the lee side of the Andes, these storms propagate further eastward as they grow up to the mature stage into mesoscale convective systems, fed by moisture provided by a strengthened South American Low Level Jet, the development of a low level pressure on the lee side of the Andes and a mid-level trough. In the context of the ongoing Flagship Pilot 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 forcing associated with the occurrence of extreme precipitation events over SESA. For that purpose, three individual 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. Two types of simulations were performed: the ?weather mode?, based on 72-hours simulations of the individual cases, and the ?climate mode?, based on 6- months-length simulations for the period from October 2009 to March 2010. The RCMs included in this first assessment are: RegCM4 (Univ. of Sao Paulo -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 terms of the triggering mechanisms associated with the extreme precipitation events is discussed. It was found that one of the largest differences among the two groups of simulations is in the low- level moisture flux convergence field, suggesting that the low-level wind and moisture fields are affected by the occurrence of convection and they are sensitive to how convection is captured in the models.