Exploring the impacts of the tropical Pacific SST on the precipitation patterns over South America during ENSO periods |
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Authors: | C A S Coelho C B Uvo T Ambrizzi |
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Institution: | Departamento de Ciências Atmosféricas, Instituto de Astronomia Geofísica e Ciências Atmosféricas, Universidade de S?o Paulo, S?o Paulo, Brasil, BR International Research Institute for Climate Prediction, Palisades, NY, USA, US
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Abstract: | Summary
Previous studies on precipitation over South America that strongly support the existence of links between precipitation and
SST anomalies in the Pacific Ocean have identified specific regions where the ENSO signal is particularly stronger. Northeast
of Brazil and some parts of southern South America are examples of these regions. However, the same attention was not taken
to identify which regions in the Central and East Pacific ocean are better correlated with the South America precipitation
during extreme ENSO events, and also which are the transition regions of the precipitation signal over South America during
these events.
Coincident periods of ENSO events for both SST over the tropical Pacific ocean and monthly precipitation sums from many observational
stations over South America were selected and analyzed. Two statistical methods were used for the data analysis: Singular
Value Decomposition (SVD) and Simple Linear Correlation (SLC). The SVD results for warmer events in the Pacific corroborate
previous ones and also clearly identified a transition region between the drier conditions in the Northeast of Brazil and
the wetter conditions in the Southeast/South of Brazil. Transition regions were also determined over Peru and central Amazon.
The SLC results indicated that the SST anomalies in the tropical east Pacific ocean has the strongest influence in the South
American precipitation during El Ni?o events. During La Ni?a events the central area of the Pacific, around 180°, has shown
a more significant influence.
Received August 10, 2000 Revised August 22, 2001 |
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