Os diferentes tipos de El Niño e seus impactos na precipitação sobre a América do Sul.

Abstract

The present work seeks to characterize the differences between the patterns of Sea Surface Temperature (SST) anomaly patterns associated with the diversity of the positive phase (El Niño - EN) of the El Niño - Southern Oscillation (ENOS) phenomenon, as well as to assess its impacts on precipitation over South America. For this, the years of El Niño events were selected within the period 1950-2019, and classified according according to their intensity (Strong El Niño), location (El Niño Modoki and Canonical) and duration time (Successive El Niño). Then, the analyses of seasonal compositions and compositional differences for the anomalies of Sea Surface Temperature, precipitation, Potential Velocity and Current Function Current at 200 hPa, Omega at 500 hPa and vertically integrated moisture flux and its divergence. and its divergence. Compositions of Sea Surface Temperature anomalies reproduce the characteristics associated with the event selection method, and show that, relative to the average of all events, strong El Niño events exhibit an intensification of the east-west sea surface temperature gradient over the equatorial Pacific over the equatorial Pacific from its initial phase until its decay, the strong El Niño events show an Modoki El Niño events show a cooling over the eastern Pacific, while canonical El Niño events did not show distinct canonical El Niño events showed no distinct characteristics from the average behavior of the surface temperature anomalies over the tropical Pacific and the successive El Niño events show a cooling over the Successive El Niño events reveal a weakening of the El Niño along its evolution, evolution, except in the austral winter. The differences in the evolution patterns of El Niños influence seasonal precipitation over South America differently. For strong El Niños there is an intensification of positive anomalies in response to the event, while over the affected regions a decrease in rainfall, changes in the intensity or positioning of the anomaly centers are observed. centers of precipitation anomalies are observed. For El Niños Modoki larger variations occur in the tropical region with the weakening of the typical El Niño response, while for successive El Niño events a weakening of the typical negative/positive negative/positive anomalies in response to El Niño is observed. These changes in the patterns of precipitation anomaly patterns are associated with differences in the patterns of Sea surface temperature anomaly patterns related to the different types of El Niño, that affect the intensities of the Walker circulation and Rossby waves, which modulate the regional circulation