Relação entre a precipitação no Nordeste do Brasil e as anomalias de temperatura da superfície do mar dos oceanos Atlântico e Pacífico Tropicais.

Abstract

In this study different statistical techniques were utilized to analyze the relations between the rainy season of the "Northeast Brazil" (NEB) and the "sea surface temperature" (SST) anomalies of the tropical Atlantic and Pacific oceans for the period 1970-1988. reliminary correlations between the precipitation indices of the rainfall regimes of the north, east and south of NEB and SST anomalies were obtained. The results suggest the identification of relevant harmonics of the SST anomaly series. These series which were subjected to the harmonic analysis evidenced five significant harmonics, following the test of Fisher, with the approximate periods of 1, 2, 6, 10 and 19 years for the Atlantic and 2, 2.5, 4, 5 e 19 years for the Pacific. These harmonics explained a total variation of 65% and 78%, respectivety, for the Atlantic and the Pacific. The correlations of the series composed of the sum of the periodicities and the precipitation amount of each and every rainfall station delimited the areas of possible forecast, which comprises the whole north of NEB. The technique of principal component analysis applied to the forecastable series of the Atlantic and Pacific SST anomalies showed that the first and second components, which represent about 98% of the total variance can be substituted by SST anomalies with a lag of two months. The analysis of regression as a function of the SST anomaly forecastable series defined in the principal component analysis, showed that about 50% of the precipitation variability can be explained by this model. Within the limitations of the model, a prognostic tendency was worked out for the subsequent years of 1988.