Variability in warm-season atmospheric circulation and precipitation patterns over subtropical South America: relationships between the South Atlantic convergence zone and large-scale organized convection over the La Plata basin

摘要: Warm-season precipitation variability over subtropical South America is characterized by an inverse relationship between the Atlantic convergence zone (SACZ) and central western La Plata basin of southeastern America. This study extends analysis this “South American Seesaw” dipole to relationships SACZ large, long-lived mesoscale convective systems (LLCSs) basin. By classifying events into distinct continental oceanic categories building a logistic regression model that relates LLCS activity across region precipitation, detailed account spatial in out-of-phase coupling large-scale organized convection provided. Enhanced found result increased northern, northeastern, sections basin, association with poleward atmospheric moisture flux from Amazon toward these regions, decrease probability occurrence Increased however, was strongly related reduced decreased nearly entire These results suggest northern eastern are closely tied transport while warm coastal Brazil Current may also play important role as evaporative source for LLCSs