Atmospheric circulation features associated with the precipitation variability over the south region of Northeast Brazil

The atmospheric circulation features associated with the precipitation variability during the main rainy period (NDJ) of the south region of Northeast are determined through the ACP and Cluster analyses. Daily precipitation data and NCEP reanalysis data are used. The meteorological summer systems of South America, as well as the phenomena associated with their variability, such as ENSO, are identified. Positive (negative) anomalies of precipitation in the south region of Northeast are related to the positive (negative) phase of ENSO. It is pointed out that the wet pattern is related to the shift of the South Atlantic Convergence Zone (SACZ) northward and the South Pacific Convergence Zone (SPCZ )eastward. The rainy patterns are also associated with the tropical upper cyclonic vortex situated over the Atlantic Ocean, intense convection over the east region of Amazon and shift of the Bolivian High to the east. The flow at low levels is directed from the Amazon to the south region of Northeast and there is intensification of the northeast trade winds over the northern coast of South America. The dry pattern is associated with the SACZ displaced southwards and the tropical upper cyclonic vortex either close or over the continent. In this case, the Bolivian High is displaced to the west of its climatological position and the wind flow at low levels over South America is directed to southeast Brazil.