Atmospheric circulation and moisture transport associated with large-scale organized convection over subtropical South America

Abstract

Precipitation variability in the La Plata river basin of subtropical South America has wide-ranging social and economic implications. There is a well-documented out-of-phase relationship between precipitation in this region and in the South Atlantic Convergence Zone (SACZ), but few studies have investigated relationships between the SACZ and large, long-lived convective systems (LLCSs) that produce much of the annual precipitation over the La Plata basin. Additionally, the widespread presumption that these LLCSs are primarily initiated by moisture from the Amazon basin has heretofore received little scrutiny. This thesis demonstrates that active phases of the continental and oceanic portions of the SACZ have distinctly different relationships with La Plata LLCSs, and that the oceanic SACZ is more strongly related to LLCS activity over most of the La Plata basin. Results also suggest that regions other than the Amazon often contribute moisture to La Plata basin LLCSs, a finding that warrants further investigation.