Relationship between daily atmospheric circulation patterns and South Atlantic Convergence Zone (SACZ) events

Abstract

This study presents the daily atmospheric circulation patterns at surface and altitude related to the South Atlantic Convergence Zone (SACZ) events that occurred between 2007 and 2017. For this analysis, Principal Pattern Sequence Analysis (PPSA) and sea level pressure and geopotential height reanalysis were used. Four typical atmospheric circulation patterns associated with SACZ episodes were identified. Three of them are related to the propagation of a cold front toward southeastern Brazil with a post-frontal anticyclone moving over the Atlantic Ocean. The fourth pattern is associated with the presence of a cut-off low centered over the central-south region of Brazil that induces moisture transport from the Atlantic Ocean and from the Amazon basin to most of southeastern Brazil. Considering the first three patterns, they represent, respectively, a frontal wave, a classical cold front, and a slow-moving cold front. All of these patterns provide permanent northwesterly winds in the lower troposphere over southeastern Brazil from two days before the SACZ occurrence.