Interannual variability of Tropical Atlantic and its influence on extreme precipitation events: Focus on the Amazon Basin

• Main Author: López, Katherine Lisbeth Ccoica
• Other Authors: Hallak, Ricardo
• Format: Other/Unknown Material
• Language: English
• Published: Biblioteca Digital de Teses e Dissertações da USP 2020
• Subjects: análise de clusters; variabilidade interanual da SST; variabilidade da chuva; precipitação extrema; variabilidade interdecadal da SST; índices oceânicos; interdecadal SST variability; interannual SST variability; rainfall variability; extreme precipitation; cluster analysis; oceanic indices; Pacific; North Atlantic; South Atlantic Ocean
• Online Access: https://www.teses.usp.br/teses/disponiveis/14/14133/tde-27072020-135440/; https://doi.org/10.11606/D.14.2020.tde-27072020-135440

This study provides a detailed analysis, in the interannual time-scale, of the influence of the tropical Pacific and the Atlantic Ocean in the precipitation regime over South America, with a focus on the Amazon Basin. For this purpose, first, monthly sea surface temperature data is used to determine the principal modes of variability in three Atlantic regions: Tropical North Atlantic (TNA), Tropical South Atlantic (TSA), and Subtropical South Atlantic (STSA). These patterns are obtained from Empirical Orthogonal Function (EOF), where the first mode (PC1) of each region explains the interannual variability in high percentage. The PC1 time series also shows SST peaks related to extreme precipitation events in the Amazon Basin. In addition, the Pacific and Atlantic interaction was analyzed by moving correlations and cross-wavelets for the 1880-2017 period, using Pacific indices (E and C index) and the PC1 of each Atlantic region. We found that the Atlantic regions have been coupling and decoupling in specific periods. Likewise, the Pacific and the Atlantic oceans have been shown in-phase or in opposite phase in different periods of time and frequencies. Precipitation from satellite and combined observed-satellite for the 1940-2010 period were used to identify regions influenced by the Pacific and Atlantic SST. The results suggest that different El Niño Southern Oscillation (ENSO) flavors mainly impact precipitation during the onset (October-November) and peak (December-February) of the South America Monsoon System (SAMS). We have also shown that anomalous conditions over the Tropical North and South Atlantic Ocean impact precipitation regimes during the demise (March-April) and the absence of the SAMS (May-September), while the Subtropical South Atlantic impacts in precipitation during the peak and the absence of the SAMS. Additionally, moisture flux, its divergence, and vertical structure over South America and the adjoining oceans were obtained for different conditions of tropical oceans, through the oceanic ...