Influence of the Sea Surface Temperature Decadal Variability on Tropical Precipitation: West African and South American Monsoon

Abstract

The Sahel is the semiaridWest African region between the Sahara desert and the wet tropical savanna. The Sahel rainfall depends on the West African Monsoon (WAM) system and peaks between July and September. The rainfall regimes of the Amazonia and Northeast regions, located in northern Brazil, depend on the South American Monsoon system. The Amazonia is the region covered by the Amazon River basin, where heavy rains occur throughout the year but with a rainier season extending from December to May. The Northeast is a semiarid region with a short rainy season between March and May. Precipitation regimes in these three regions have undergone changes over time with important humanitarian, environmental and economic consequences and have been a major topic of study (e.g. Rodriguez-Fonseca et al., 2015; Zhou and Lau, 2001; Marengo et al., 2016). At decadal-to-multidecadal time scales, these changes have been mainly associated with the global sea surface temperature (SST) variability. Particularly, the Sahel precipitation has been associated with the global warming (GW), the Atlantic Multidecadal Variability (AMV) and the Interdecadal Pacific Oscillation (IPO) modes of decadal-to-multidecadal SST variability (e.g. Mohino et al., 2011a). The Amazonia and Northeast rainfall changes have been related to the Pacific and the Atlantic SST variability at decadal time scales (e.g. Grimm and Saboia, 2015), which is led by the AMV and IPO. Climate study through Global Circulation Models (GCMs) is crucial to understand climate changes and assessing its effects. So, in the first part of this Thesis a multi-model analysis is done addressing the influence of the main decadal-to-multidecadal modes of SST variability on precipitation in the Sahel, Amazonia and Northeast using different GCMs simulations from the 5th phase of the Coupled Model Intercomparison Project (CMIP5) (Taylor et al., 2012)...