Precipitação em verões sob influência de eventos ENOS canônico e Modoki no sudeste da América do Sul

Abstract

Extreme climatic events of rainfall occurring in Southeastern South America (SESA) are commonly related to the occurrence of "El Niño - Southern Oscillation" Events (ENSO). The ENSO can be identified by the variation of Sea Surface Temperature (SST), that can occur in the Pacific Ocean region called the East Equatorial (Canonic ENSO) and in the Central Pacific (Modoki ENSO). Both result in different precipitation anomalies in several areas of the globe, such as SESA. The objective of this research was to expand the studies on the effects of the ENSO Modoki, proposing to identify them and compare them to the ENSO Canonic, observing the implications in the alteration of atmospheric circulation that lead to precipitation anomalies on the SEAS. In order to identify the Canonic and Modoki phenomena, we used climatic indices and SST anomalies maps for the period of DecemberJanuary-February (DJF). After identifying the types of events, simple linear correlation calculations were developed between the Oceanic Niño Index (ONI) and the precipitation anomalies of the region in question for the years identified in the previous stage. Precipitation anomaly maps based on Reanalysis data completed the list of images for comparison with SST anomalies. In some Modoki years, their responses are within the expected range for the warming phase, with positive precipitation anomalies as well as in cooling phases with negative precipitation anomalies. However, in SESA, the reversal of the precipitation anomaly signal during Modoki events is apparent, since, with the expected warming (cooling) of the Pacific would be an increase (decrease) in the volume of rainfall, besides the inversion, also a displacement of the signal to the Atlantic, results of El Niño Modoki and La Niña Modoki. It is also interesting that in canonical years the inversion also happens. The studies also indicated that the common generic mention of SESA as being a homogeneous area of ENSO-related precipitation anomaly begins to fall. It was possible to identify four distinct areas that have also distinct anomalies, often contrary during the same ENSO event.