Variability of the Atlantic Intertropical Convergence Zone during dry and rainy seasons of tropical South America

Abstract

During the summer and early of austral autumn, several regions of Brazil suffer periods of intense precipitation generally associated with the South Atlantic Convergence Zone (SACZ) and with the Intertropical Convergence Zone (ITCZ), respectively. The SACZ acts in southeastern Brazil, northern Paraná and Central Brazil and the ITCZ mainly acts in eastern Amazon (EA) and northern Northeast of Brazil (NNB). Both of them are among the main systems that cause high precipitation amounts, and they are linked through mechanisms associated with a Hadley-type circulation. Thus, SACZ and ITCZ must have reciprocal relationships regarding to position and intensity of the convection during austral summer and early phases of austral autumn, when the SACZ is not active anymore and the ITCZ has most influence over NNB and EA. Intraseasonal phenomena, as Madden-Julian Oscillation (MJO), are important modulators of the precipitation in South America, influencing the SACZ phase (active/break) and the position of ITCZ. Thus, the general purpose of this work is to identify relationships between the position of ITCZ and periods of active and break phases of SACZ and between the intensities of the convective activity associated with these two systems. We intend also to identify characteristics in SACZ that can work as predictors of the quality of the rainy season of NNB (February to May), that is associated with ITCZ. This study will be carried out with detailed statistical analysis. Using an atmospheric numerical model we intend to simulate and analyze the mutual impact between the convection associated with ITCZ and SACZ. Regarding to teleconnections patterns, the objective of this research is to study the influences of MJO in the precipitation over South America, and particularly in the onset/demise of rainy season of NNEB.