O objetivo deste trabalho foi correlacionar a precipitação (março a julho) de um grupo de postos homogêneos do setor leste do Nordeste do Brasil (NEB) com Anomalia de Temperatura da Superfície do Mar (ATSM) e identificar áreas de influência deste parâmetro nas chuvas da região. O período de estudo foi de 1945 a 1985 e a análise mostrou influência do Atlântico e Pacífico sobre as chuvas do setor leste, sendo a correlação do Atlântico maior, principalmente na área do Dipolo (correlação maior que 0,6, significativa a p < 0,05). Os modos zonal e meridional, descritos por Servain & Arnault (1995) foram detectados durante análises feitas com defasagem temporal ("lags"). No Oceano Pacífico Tropical Leste se encontrou correlações negativas indicando a presença dos ramos descendentes da célula de Walker no setor leste do NEB.

The atmospheric structure over north‐east Brazil during anomalous rainfall years is studied in the 11 levels of the outputs of the Laboratoire de Météorologie Dynamique atmospheric general circulation model (LMD AGCM). Seven 19‐year simulations were performed using observed sea‐surface temperature (SST) corresponding to the period 1970– 1988. The ensemble mean is calculated for each month of the period, leading to an ensemble‐averaged simulation. The simulated March‐April rainfall is in good agreement with observations. Correlations of simulated rainfall and three SST indices relative to the equatorial Pacific and northern and southern parts of the Atlantic Ocean exhibit stronger relationships in the simulation than in the observations. This is particularly true with the SST gradient in the Atlantic (Atlantic dipole). Analyses on 200;hPa velocity potential, vertical velocity, and vertical integral of the zonal component of mass flux are performed for years of abnormal rainfall and positive/negative SST anomalies in the Pacific and Atlantic oceans in March–April during the rainy season over the Nordeste region. The results at 200 hPa show a convergence anomaly over Nordeste and a divergence anomaly over the Pacific concomitant with dry seasons associated with warm SST anomalies in the Pacific and warm (cold) waters in the North (South) Atlantic. During drought years convection inside the ITCZ indicated by the vertical velocity exhibits a displacement of the convection zone corresponding to a northward migration of the ITCZ. The east–west circulation depicted by the zonal divergent mass flux shows subsiding motion over Nordeste and ascending motion over the Pacific in drought years, accompanied by warm waters in the eastern Pacific and warm/cold waters in northern/southern Atlantic. Rainfall variability of the Nordeste rainfall is linked mainly to vertical motion and SST variability through the migration of the ITCZ and the east–west circulation.

The relationship between interannual variability of rainfall in north‐east Brazil and tropical sea‐surface temperature is studied using observations and model simulations. The simulated precipitation is the average of seven independent realizations performed using the Laboratoire de Météorologie Dynamique atmospheric general model forced by the 1970–1988 observed sea‐surface temperature. The model reproduces very well the rainfall anomalies (correlation of 0ċ91 between observed and modelled anomalies). The study confirms that precipitation in north‐east Brazil is highly correlated to the sea‐surface temperature in the tropical Atlantic and Pacific oceans. Using the singular value decomposition method, we find that Nordeste rainfall is modulated by two independent oscillations, both governed by the Atlantic dipole, but one involving only the Pacific, the other one having a period of about 10 years. Correlations between precipitation in north‐east Brazil during February–May and the sea‐surface temperature 6 months earlier indicate that both modes are essential to estimate the quality of the rainy season.

Objetivou-se, com este estudo, relacionar a precipitação no setor leste do Nordeste do Brasil (NEB) com a Temperatura da Superfície do Mar (TSM) nos oceanos Atlântico (área do Dipolo) e Pacífico, no período de 1945 a 1985. Através dessa análise pode-se ter uma idéia de como os episódios com anomalias de TSM influenciam na pluviometria da costa leste do NEB (que se estende do Rio Grande do Norte à Bahia). Os resultados mais significativos foram os seguintes: em anos com gradiente de temperatura negativo no Atlântico, aqui também chamado gradiente desfavorável, as chuvas ocorreram abaixo da média de longo período nos estados do Rio Grande do Norte (84%) e Paraíba (74%); em anos com gradiente de temperatura neutro, as chuvas foram normais ou acima do normal na Paraíba (73%); em anos com gradiente de temperatura positivo no Atlântico, aqui também chamado gradiente favorável, as chuvas ocorreram na média e acima da média de longo período, nos Estados de Alagoas (73%), Sergipe (73%) e Bahia (73%).