Escoamentos de retorno de umidade na Bacia do Prata

Abstract

This study evaluated the seasonality of moisture supply on part of the Bacia do Prata (BP) in the context of transient anticyclones east of the Andes, phenomenon that receives the name of moisture return (RU). This phenomenon has two main phases: first, occurs the approach of a transient anticyclone and establishment of air cold and dry mass on the study region and the second with the return to this region of a warm and moist air due to displacement of transient system for lower latitudes in the South Atlantic. Were utilized Reanalysis of Climate Forecast System Analisys (CFSR) data for the period between 1990 and 2009. For the selection of candidates a RU were analyzed time series in four different sectors of the BP of the following variables: reduced pressure at mean level sea (PNM), specific humidity integrated between 1000 and 700 hPa (Uint), meridional wind at 850 hPa (V850) and air temperature at 1000 hPa. Then the candidate events undergo a synoptic analysis for selection only of the cases RU. For the confirmed cases were performed seasonal analysis of the synoptics field average of the variables temperature and specific humidity at 850 hPa (T850 e q850), V850 e PNM e the thickness between geopotential heights 500 hPa and 1000 hPa (ESP) and also was calculated the divergence of moisture flux vertically integrated in a domain that defines part of BP. Lastly, rainfall estimates by remote sensing by the method Center Morphing Method (CMORPH) between 2003 and 2009 were used to determine the seasonal pattern of rainfall in BP and in each of the sectors used in this work. The results show greater number of RU events in the winter months followed by spring, Also in the winter is observed changes more intense air masses between different phases of the RU and a higher moisture effectiveness for BP in the in phase 2 of RU. The precipitation in phase 2 of RU contributed to more intense rainfall in summer and in winter it is important for the total number of days with precipitation.