Observational data analyzed in this study showed that the rainy season during 1992 and 1994
years were characterized by a seasonal precipitation pattern predominantly drier and wetter
than normal, respectively, in association with unfavorable (favorable) SST conditions verified
in the intertropical Atlantic. Based on case studies, the intraseasonal variations (as estimated
from weekly means) of tropical convection and precipitation over Amazon and Brazil
Northeast related to propagation of the Madden-Julian oscillation (OMJ), before and during
its passage through South America were investigated. The results showed that there are
significant intraseasonal variations induced by the OMJ, independent of the Atlantic seasonal
modulation to be favorable or unfavorable to the seasonal precipitation. Therefore, even in
years with abundant rainfall observed during the rainy season (as observed in 1994) or with
deficient rainfall (as observed in 1992), the passage of OMJ can effectively change the
convective activity associated with Inter Tropical Convergence and Zone and Convergence
Zone of the South Atlantic and thus change the sign of regional precipitation.
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