Impacto dos oceanos Pacífico e Atlântico no clima do Nordeste do Brasil.

Abstract

The impact of climatic events in thePacific (mainlyEl Niño and La Niña) and in the tropical Atlantic (meridional gradient of the SST anomaly) on the Northeast Brazil (NEB) precipitation was analysed, more specifically on three climatic sub-regions (north, east and center/south), from the analysis of composites and creation of scenarios. The analysis included observed precipitation (in situ and satellite data), simuled precipitation for MCGA ARPEGE, beyond data gotten from NCEP reanálises. The ARPEGE was run with two different configurations of the SST for the period 19481997: the first one, GOGA, was forced by observed SST on the Global Ocean; the second one, AOGA, was forced by observed SST on the Atlantic and climatic SST on the two other oceans. The model succeeded to represent the variability of the precipitation in the years of the events since the two types of simulation helped to identify the differentiated influence between the SST conditions over the Pacific and Atlantic on the precipitation variability in the three studied sub-regions. The results showed that during El Niño years, if the conditions of the Atlantic are unfavourable (favourable), the impact on the north and east sub-regions is a below (around or above) precipitation from average in the rainy season. The opposite was verified during La Niña years. The simulations of ARPEGE can capture these patterns that are GOGA better reproduce the precipitation for these years that SSTA in the Pacific and North Atlantic have the same signal and AOGA for the SSTA with different signals. The exception occurred in the sub-region east where AOGA was better than GOGA, suggesting that the Atlantic dominates the variability of the precipitation in the east of NEB during La Niña years. For the sub-region center/south it was noted that the simulations did not reproduce very well the precipitation during El Niño/La Niña years. Furthermore, the impact in that sub-region center/south is opposed to that of east and north sub-regions. It can be argued that the Atlantic determines with the strongest impact the rain behavior in the three NEB sub-regions. However that impact does not seem as well the consequence of the meridional gradient, as the direct SST anomaly situationinthesoutherntropical basin.