Variabilidade sazonal da precipitação no sudeste da América do Sul associada com as fases da oscilação decenal do Pacífico

Abstract

The phenomena that most cause climate variability are those related to the oscillation of Sea Surface Temperature (SST). SST oscillations affect continental climates through a physical process known as atmospheric teleconnections. Studies of atmospheric teleconnections and their influences on the horizontal structure of atmospheric circulation can be useful for understanding the occurrence of anomalous rainfall or temperature events in various regions of the globe. Among the teleconnection phenomena that cause global climate variability is the Pacific Decadal Oscillation (PDO). The PDO is a pattern of decadal variability (30-40 years) that can modulate the effects of other areas of oceanic anomalies, such as the El Niño/Southern Oscillation (ENSO), in defining the climate variability of Southeast South America. Therefore, studies on the PDO are important in the scenario of climate projections of intensified ENSO events and general warming of global oceans. Thus, this research aims to analyze whether the different phases of the PDO influence precipitation patterns in Southeast South America (SESA), considering the different seasons of the year. The specific objectives are: a) to demonstrate the patterns of precipitation anomalies caused by the PDO for the southeastern region of South America; b) to analyze if there are differences in the effects of the PDO for different seasons of the year. Annual precipitation anomaly maps were developed for each phase of the PDO adopted in the research, namely: a) cold phase, 1950 to 1976; b) warm phase, 1977 to 1996; c) cold phase: 1997 to 2019. Maps were also developed for the 4 seasons of the year for each phase of the PDO. The results show that in the center of South America, there is an inverse pattern of precipitation anomalies in each phase of the PDO, with negative anomalies during cold phases and positive anomalies during warm phases. As for SESA, a positive trend in precipitation was observed during the analyzed period. In other words, it was identified that the PDO does not exert influence on precipitation anomalies in SESA, but rather a positive trend is observed, which also cannot be explained by another element of climate variability, such as El Niño, but is a result of the oceanic warming process in the equatorial region of the planet, with the expansion of the tropical region.