Dynamics of Precipitation Anomalies in Tropical South America: A Multiscale Approach

Abstract

This PhD thesis aims to study the dynamics of precipitation anomalies and extreme precipitation events in tropical South America (TrSA). Precipitation anomalies in TrSA are influenced by a complex climate variability resulting from the superposition of various phenomena acting on different temporal and spatial scales, as well as several geographical features. The study uses interpolated gridded global datasets and climate reanalysis to understand dynamics of precipitation anomalies, while weather radar data and last-generation reanalysis datasets were employed to investigate extreme precipitation events. The study applied data analysis techniques and machine learning algorithms and incorporated process knowledge to select the input data and interpret the results. Three objectives were executed to understand precipitation anomalies and extreme precipitation events in TrSA using a multiscale perspective: 1) understanding the dynamics of precipitation anomalies in tropical South America in annual to monthly scales, 2) understanding the dynamics of precipitation anomalies in the tropical Andes in seasonal scale, and 3) understanding the dynamics of extreme precipitation at event scale in the southern Ecuadorian Andes. The study found that precipitation anomalies are mainly influenced by the intensity and position of the South Atlantic Convergence Zone (SACZ), El Niño Southern Oscillation (ENSO), the meridional position of the Intertropical Convergence Zone (ITCZ), and the strength of the South American Monsoon System. Moreover, Convective Available Potential Energy (CAPE), the vertical integral of divergence of moisture flux, and SSTbased oceanic indices were found to be important variables that influence precipitation anomalies in different regions of the tropical Andes. Finally, the study found distinct patterns of circulation anomalies for extreme events in the southern Ecuadorian Andes.