Physics Features of the Mesoscale Convective Systems that reached the Rio Grande do Sul from 2004 to 2008

A passagem de Sistemas Convectivos de Mesoescala (SCM) sobre uma regi??o causa impactos em superf??cie, pois geralmente est?? associada ?? precipita????o intensa, fortes rajadas de vento e granizo. Esse fen??meno bastante comum na regi??o sul do Brasil afeta o Rio Grande do Sul (RS) e causa preju??zos a sua economia. Portanto o estudo dos SCM que atingem o RS ?? de grande import??ncia, pois al??m de permitir um maior entendimento do tempo e do clima da regi??o tamb??m fornece subs??dios aos tomadores de decis??o. Assim, o objetivo deste trabalho foi estudar as caracter??sticas f??sicas sazonais dos SCM cuja g??nese e manuten????o ocorreu ao sul de 20??S, que apresentaram ciclo de vida de no m??nimo 6 h, que tiveram nascimento espont??neo e dissipa????o normal e que afetaram a regi??o que cobre o RS durante o per??odo de 2004 a 2008, utilizando a t??cnica ForTrACC (Forecasting and Tracking of Active Cloud Clusters). Foram utilizadas as imagens brutas do sat??lite GOES (Geostationary Operational Environmental Satellite) do canal 4, com resolu????o espacial no seu ponto subsatelite de 4 km x 4 km e resolu????o temporal de ?? hora, do per??odo de 01/01/2004 a 31/12/2008. Essas imagens foram fornecidas pela Divis??o de Sat??lites Ambientais do Centro de Previs??o de Tempo e Estudos Clim??ticos do Instituto Nacional de Pesquisas Espaciais (DSA/CPTEC/INPE) e serviram como base de dados para a utiliza????o da t??cnica ForTrACC. Os resultados para o per??odo de estudo mostraram que: i) os SCM que afetaram o RS apresentaram maior n??mero de ocorr??ncia no per??odo mais quente do ano (JFM); ii) nos quatro trimestres do per??odo de estudo a maioria dos SCM que afetou o RS (64,7%) apresentaram tempo de vida entre 6 e 12h; iii) SCM com maior tempo de vida cobrem ??reas maiores; iv) a temperatura m??nima (Tir) apresentou valores m??dios menores nos SCM observados em JFM e OND; v) em todos os per??odos do ano em torno de 6,4% dos SCM apresentaram formato mais linear, aproximadamente 64,0% apresentaram formato irregular e em torno de 29,6% apresentaram formato mais circular; vi) valores menores de Tir est??o relacionados ?? SCM com formato mais pr??ximo do formato circular (excentricidade igual ou maior do que 0,5) e com maior dura????o; vii) as 3 fases do ciclo de vida dos SCM que afetaram o RS podem ocorrer de forma distribu??da ao longo do dia; viii) em todos os per??odos do ano os nascimentos dos SCM que afetaram o RS ocorrem predominantemente dentro e em torno da grade que cobre o RS, com tend??ncia a iniciarem mais no lado oeste da grade sobre o continente; ix) em todos os trimestres h?? uma tend??ncia de a trajet??ria m??dia preferencial ser de oeste para leste.The happening of Mesoscale Convective Systems (MCS) over a region causes impacts on the surface, that is usually associated with heavy precipitation, strong wind gusts and hail. This phenomenon is common in southern Brazil reach the Rio Grande do Sul (RS) and causes damage to its economy. Therefore the MCS study that reaching of RS is of great importance, as well as allowing a greater understanding of weather and climate of the region also provide knowledge to decision makers. Thus, the aim was to study the seasonal physics features of MCS whose genesis and maintenance happened southward of 20 ?? S, with life cycle of at least 6 h, with spontaneous initiation and normal dissipation and that reached the region covering the RS from 2004 to 2008, using the FORTRACC method (Forecasting and Tracking of Active Cloud Clusters). Channel 4 Geostationary Operational Environmental Satellite (GOES) images from 2004/01/01 to 2008/12/31, with 4 km x 4 km spatial resolution in your subsatellite point and ?? hour temporal resolution were used. These images were provided by DSA/CPTEC/INPE (Satellite Division and Environmental Systems/Center for Weather Forecast and Climate Studies/National Institute for Space Research) and served as a database for the use of the FORTRACC method. The results showed that: i) the MCS that affected the RS occurring majority in the warmest quarter of the year (JFM), ii) in the four quarters of the study period most of the MCS that affected the RS (64.7%) had lifetime between 6 and 12 h, iii) MCS with longer life cover larger areas, and iv) the minimum temperature (Tir) had lower mean values observed in the MCS in OND and JFM, v) in all periods of the year around 6.4% of the MCS showed a more linear format, approximately 64.0% have irregular shape and about 29.6% had more circular shape, vi) lower values of Tir are related to MCS with shape close to circular (eccentricity equal to or greater than 0.5) and longer duration, vii) the three phases of the life cycle of MCS that affected the RS can occur in a distributed manner throughout the day, viii) in all periods of years the births of MCS that affected RS occur predominantly in and around the grill that covers the RS, with a tendency to start over on the west side of the grid on the mainland; ix) in all quarters there is a tendency for the mean trend preferential be from west to east