Padrões Decenais do Gradiente Inter-Pacífico-Atlântico e a Precipitação da América do Sul

Abstract

The Pacific and Atlantic Tropical oceans are responsible for most of the climate variability in the tropical region. Even though independent, they can form together an interannual variabil ity mechanism called the Inter-Pacific-Atlantic gradient, which is also modulated in decadal scales by the positive and negative phases of the Atlantic Multidecadal Oscillation (+AMO and -AMO). The present work investigated the variations in the associated atmospheric and oceanic patterns during austral winter through both AMO phases and its impacts on South America’s (SA) Precipitation anomalies (APRP). Results show that this phenomenon is a dominant vari ability mode during austral winter, characterized by Sea Level Pressure anomalies (SLPA) and Sea Surface Temperature anomalies (ASST) gradient between both tropical oceans. Selection of extreme events shows an equal distribution of positive events (+PC1) for both phases while the negatives (-PC1) are more frequent during -AMO. +PC1 events during +AMO are charac terized by an west-east ASST gradient made by the anomalous cooling (warming) of Tropical Pacific (Atlantic), especially at Central Pacific (Tropical North Atlantic, responsible for posi tive (negative) APRP at SA’s Extreme-North (Central-West and South) region. +PC1 events in -OMA are equatorially confined and show similar impacts in SA’s rainfall. The ATSM gradi ent becomes east-west for -PC1 events due to Tropical Pacific (Atlantic) anomalous warming (cooling), even though they are equatorially confined only during +AMO periods. These events are related to positive (negative) APRP for the Center-West and South-Southeast (North) SA regions during both phases. Results show that different oceanic and atmospheric patterns com pose the Inter-Pacific-Atlantic sector’s variability, which impacts SA’s rainfall significantly and can be felt though the entire continent.