Precipitation response to El Niño/La Niña events in Southern South America. Emphasis in regional drought events

OLGA PENALBA; JUAN ANTONIO RIVERA

Guayaquil

Conferencia; III International Conference on ENSO; 2014

Centro Internacional para la Investigación del Fenómeno de El Niño

The ENSO phenomenon is one of the key factors that influence the interannual variability of precipitation over Southern South America (SSA). The aim of this study is to identify the regional response of precipitation to El Niño/La Niña events, with emphasis in drought conditions. The standardized precipitation index (SPI) was used to characterize precipitation variabilities through the 1961-2008 period. In order to identify the regional influence of El Niño and La Niña events on the SPI time series, we calculated the mean SPI values for the El Niño and La Niña years and assessed its significance through bootstrap analysis. We found coherent and significant SPI responses to ENSO phases in most of the seven regions considered, mainly for the 12 months SPI time series. The precipitation response to La Niña events is characterized with precipitation deficits, identified with negative values of the SPI, although the signal is not as clear as in the cases of El Niño events. During the year of development of El Niño events, it is expected to have precipitation deficits mainly in the central portion of SSA during the autumn season.