| Summary: | Rainfall variability over the tropical Atlantic region is dominated by changes in the surfacetemperature of the surrounding oceans. In particular, the oceanic forcing over Northeast ofSouth America is dominated by the Atlantic interhemispheric temperature gradient, whichleads its predictability. Nevertheless, in recent decades, the SST influence on rainfall variabilityin some tropical Atlantic regions has been found to be non-stationary, with important changesof the Atlantic and Pacific influence on Sahelian rainfall which appear to be modulated atmultidecadal timescales. In this work, we revisit the SST influence over Northeast of SouthAmerica including the analysis of the stationarity of this relationship at interannual timescales.Principal Component Analysis has been applied to the interannual component of rainfallduring the March-April-May season. Results show how the SST forcing on the first mode ofrainfall variability, which is a dipole-like pattern generated by the changes in the seasonalmigration of the Intertropical Convergence Zone, is different depending of the consideredperiod. The response to the SST anomalies in the Pacific basin is opposite to the Atlantic oneand affects different areas. The Atlantic Niño influences rainfall variability at the beginning ofthe XX century and after 1970, while the Pacific Niño plays a major role in the variability ofthe rainfall in the Northeast of South America from 1970 onwards. The combined effect of bothbasins after the 1970s amplifies the anomalous rainfall response.
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