Precipitação sobre a América do Sul para uma situação de La Niña conjugada com Dipolo positivo e negativo de TSM no Atlantico em simulacoes com o MCG CPTEC/COLA

The role of the Atlantic Ocean in a La Niña episode over Northeast of Brazil is investigated using the CPTEC/COLA GCM. Two set of integration are performed using the same negative Sea Surface Temperature (SST) anomalies in the Tropical Pacific Ocean and changing the SST in the Atlantic Ocean. A positive dipole (higher than normal SST at the Tropical North Atlantic and below normal at the Tropical South Atlantic) and a negative dipole (opposite conditions), are set as boundary conditions of SST in the two experiments. Four initial conditions were integrated in each case in order to obtain two ensembles of results. When La Niña was tested conjugated with a positive dipole, the precipitation over Nordeste was below average and for the other case, using negative dipole over Tropical Atlantic, positive precipitation anomalies occurred over the whole Nordeste. Thus, the conditions over Atlantic Ocean have a greater effect on the precipitation of Nordeste than the Pacific Ocean in La Niña. In a previous study of El Niño situation, the north region of Nordeste is affected by the Atlantic SST, but other tropical areas of South America show a change only in the intensity of anomalies. Central and southeast of South America are affected by the Atlantic conditions only in La Niña situation, whereas in El Niño these regions are influenced only by the Pacific Ocean conditions.Pages: 1715-171