Tropical Atlantic Moisture Flux, Convection over Northeastern Brazil, and Pertinence of the PIRATA Network

Abstract

This study aims to examine the relationship between the tropical Atlantic latent heat flux and convective cloud coverage over northeast Brazil (NEB) during the four months of the main rainy season (February?May). The correlation with anomalies of these data is investigated, both without lag and with a 1-month lag (the heat flux in advance). In both cases, a significant positive correlation appears in the northwestern tropical Atlantic, and a significant negative correlation is obtained for a limited area off eastern NEB. These two correlation patterns are linked to anomalies in the trade wind intensity and in the meridional position of the intertropical convergence zone (ITCZ), which relate to the latent heat flux anomalies and NEB convective coverage anomalies, respectively. The positive correlation pattern is spread over a large part of the northern tropical Atlantic, whereas the negative correlation pattern is confined off NEB. This indicates the existence of different regional mechanisms in the tropical Atlantic basin. The impact of the Atlantic heat fluxes on NEB convection is somewhat different from the classical meridional dipole related to the SST variability. The analysis of the horizontal moisture flux shows that during flood years an additional meridional inflow balances the eastward loss, and the upward velocity reinforced over NEB contributes to intensify NEB convection. The positive correlation pattern indicates that the location of the northern branch of the Pilot Research moored Array in the Tropical Atlantic (PIRATA) moorings is pertinent to monitor the ocean?atmosphere interface parameters. The negative correlation pattern off NEB provides new support for the possible extension of the PIRATA array toward the Brazilian coast. Complementary results at 1-month lag and the real-time availability of the PIRATA data confirm the potential of NEB forecasting.