El Niño signal variability in the precipitation over southeastern South America during austral summer

Abstract

Some aspects of El Niño (EN) events signal in the precipitation over southeastern South America (SESA) during austral summer are examined. In February - March this signal covers most of the southeast part of SESA and has a wide range of variability in its intensity. The rainiest EN events are characterized by an intensification of the moisture flow from the amazonic forest to SESA jointly with an enhancement of the subtropical jet over South America. The dynamics in upper-levels is associated with a circulation field in the Southern Hemisphere dominated by the presence of the ENSO pattern described in previous studies. During less rainy EN events the moisture flow towards SESA diminishes; and, the structure of the ENSO pattern of circulation over South America implicates a weakening of the subtropical jet. Therefore, the characteristics of the low and upper levels circulation modulate the intensity of the rain over SESA during these events. Copyright 2004 by the American Geophysical Union.