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Atlantic modulation of El Niño influence on summertime rainfall over southeastern South America
Author(s) -
Barreiro Marcelo,
Tippmann Andrés
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl035019
Subject(s) - climatology , environmental science , oceanography , atlantic hurricane , la niña , geology , el niño southern oscillation , tropical cyclone
This study addresses the effect of Atlantic sea surface temperature (SST) anomalies on rainfall over southeastern South America during January–February, particularly during El Niño years, using observations as well as model simulations. It is found that the state of the equatorial Atlantic during El Niño years can modulate its influence on rainfall over southeastern South America, such that when the equatorial Atlantic is warm, the El Niño influence is weaker. This Atlantic influence is shown to occur through the response of the low level winds to equatorial SST anomalies: the convergence of westerly anomalies onto the warm anomaly decreases the equatorial trades and moisture flow into the Amazon and, moreover, reduces the northerly flow that brings moisture to southeastern South America. The total rainfall response in this region can thus be thought as the combination of rainfall anomalies from the equatorial Pacific and Atlantic oceans.