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Influence of isolated interannual and decadal scales on the water balance of the Amazon basin

Rildo Gonçalves de Moura*, Francis Wagner Silva Correia, José Augusto Paixão Veiga, Vinicius Buscioli Capistrano, Paulo Yoshio Kubota

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ABSTRACT: In this study, we evaluated the isolated effects of the interannual and decadal time scales on the water balance of the Amazon basin. This research is interesting because it brings the dynamical response of the water balance components to a particular ocean scale variability. For this, we used the Brazilian Global Atmospheric Model (BAM) and sea surface temperature (SST) filtration technique. The impact of the isolated interannual and decadal time scales was quantified for episodes of El Niño Southern Oscillation (ENSO) and the Atlantic Dipole (AD). The results show that isolated interannual scales weaken the impacts of El Niño and La Niña on water balance components in the north of the Amazon and northeastern Brazil. Such a weakening is more evident in the episodes of El Niño than in those of La Niña. This indicates that El Niño is more dependent on other time scales (in addition to the interannual) than La Niña. In relation to the Atlantic, the positive AD increases (decreases) the precipitation in the north (south) of the Amazon basin in the experiment with all SST time scale variabilities. On the other hand, when the decadal scale is isolated, the increase in precipitation in the north of the basin is not observed, losing the dipole pattern in the precipitation anomaly between the north and south of the Amazon basin. The BAM model is not sensitive to the negative AD when SST is isolated in the decadal scale. These results are important for monitoring the climate of humid tropical regions, mainly for the study of ENSO, since, according to recent research, these extreme events will be increasingly frequent and intense.