Avaliação da precipitação na Serra do Mar – SP em eventos de diferentes intensidade e duração

Abstract

Evaluation of precipitation at the serra do mar-sp during events with different intensity and duration. The Serra do Mar, in its longest part along the shore of the state of Sao Paulo, has, as one of its most distinctive climatologic traits, the influence of orography in the total amounts of precipitation. The configuration of obstacle and the action of atmospheric systems are responsible for total amounts of precipitation significantly different throughout its profile which, by its own right, presents different relief compartments, such as the Baixada Santista and the humid slopes of the hills and its countryside edge. The analysis of a series of precipitation events distributed according to intensity and duration shows the influence of orography by promoting total precipitation amounts that are among the highest ones in Brazil, up to areas with total amounts which, once compared to the amounts of the humid slopes, prove to be areas with rain shadows. In four events chosen throughout the year of 2005 utilizing five pluviometric posts, it has been analyzed both the hourly evolution and the accumulated precipitation for high and low intensity and also for long and short duration. The selected events show that the intensification of the orography happens, mostly, with association of atmospheric systems and the position of the measuring posts. Therefore, it has been noticed that during short duration events the variation of the total amounts of precipitation is significantly inferior to the spatial variation during the long duration events, once that, during short duration events, convective systems are predominant whereas, during long duration events, the predominance is of frontal systems, having been registered much higher total amounts of precipitation in the posts which were facing the ocean compared to those which were in the countryside posts.