Variacoes das Circulacoes Tropicais E as Anomalias de Precipitacao Associadas, Em Dois Anos de Contraste (Variations of Tropical Circulation and Associated Rainfall Anomalies, during 2 Years of Contrast)

摘要

During 1983 severe droughts were observed over large areas of tropical lands and above normal rainfall over equatorial central Pacific related to the 1982 to 1983 El Nino, while during 1984 the precipitation pattern almost reversed. The analysis of the vertical velocity, calculated using observed wind, for 1983 and 1984, showed that the intensities and locations of the ascending and descending branches of the Walker circulation were consistent with the anomalous precipitation distribution. The north-south ITCZ migration played an important role to modulate the tropical precipitation, during 1983 and 1984. The return from the El Nino atmospheric circulation features to a normal pattern seems to have started around May 1983. Seasonal changes, such as the establishment of the summer monsoon regime over the Indian Ocean and India, contributed to this return. Highly significant correlation is verified between the Southern Oscillation Index (SOI) and the atmospheric water vapor. These calculations showed negative correlations for the central Pacific stations and positive correlations for the Indonesian stations, suggesting that the water vapor variations over these regions are modulated by the Southern Oscillation. The water vapor fluctuations are synchronized to the changes of the low level divergence field, such that an increase (decrease) of the convergence causes an increase (decrease) of water vapor content.