Classification of wintertime daily atmospheric circulation patterns over Brazil

Abstract

This study presents a synoptic classification at surface and at 500 hPa during the winter (June, July, and August) over Brazil, in order to identify the main synoptic-scale meteorological systems that influence the weather of this period. Through the Principal Components Analysis (PCA) for the 1979-2020 period, it was identified five main synoptic patterns that predominated during the winter which are practically the same for each of the three analyzed months. The most frequent synoptic pattern is associated with the climatological mean-field (CMF), represented by the two of the most characteristic systems of low-level atmospheric circulation in South America: The South Atlantic Subtropical High (SASH) and the North-Western Argentinean Low (NAL). There are two other synoptic patterns related to a classical cold front over the Southern (CF_SUL) and Southeastern (CF_SE) regions of Brazil, respectively. Finally, two other synoptic patterns are associated with a blocking anticyclone (BAn) and a cyclogenetic (CG) process over the Atlantic Ocean, respectively. Both of them correspond to the most frequent synoptic pattern related to cold waves and "Friagens" over Brazil.