Respuestas del clima de América del Sur a las fases de ENSO

Résumé 0

"The high phases of ENSO, El Niño (EN), and the low phases, Anti-Niño (AN) relate differently with the precipitation regimes of South America. In order to establish the character of these relations the annual precipitation totals have been analyzed with a probabilistic approach corresponding to three sub-populations: totals of EN, totals of AN, and totals of the rest of the years, or ?normal? years. Preceeding southern summers with EN, precipitation in Central Chile and Andean Argentina is above average. During particularly strong EN events in the tropical Pacific, droughts affect Northeast Brazil during the summers and falls preceding EN. From December to March of EN years, it rains copiously along the west coast of South America between the Bay of Tumaco and Pacasmayo. In the interior of the Sierra and the Peruvian/Bolivian Altiplano droughts occur during the same period. In the Bolivian lowlands, Paraguay, south-eastern Brazilian rains are abnormally high during the southern summer and fall. In mid fall, abundant rains occur in the Rio de la Plata lowlands and in southern Brazil. The northern segment and lower basin of the Amazon experience less rains during EN and higher pluviosity during AN. The interior Amazon basin tends to react inversely as it experiences higher totals during some extraordinary EN events. Over Venezuela and Colombia under the influence of the Caribbean and North Atlantic rains during EN years are lower than normal but high during AN. Some regions of the Pampa and Patagonia do not react to EN impulses. Also independent is the behavior of rains along the central part of Brazil. Precipitation during years termed as ?normal? suggest an independence of the rain-generating mechanisms from the extreme phases of ENSO, and impose the study of anomalous precipitation associated to other tropical circulation fluctuations."