Tropical Circulations and the Associated Rainfall Anomalies during Two Contrasting Years. Revised Version

摘要

The severe drought conditions observed during 1983 over large extensions of the tropical lands were associated with the 1982 to 1983 El Nino event. In contrast, during 1984, above normal rainfall was observed over these areas. The tropical circulations were examined for these two contrasting years. The intensity and location of the rising and sinking motions were consistent with the rainfall anomalies and also with the outgoing long wave radiation anomalies. It was found that the north-south migration of the tropical trough played an important role in modulating the tropical rainfall during these two years. In the context of the currently acceptable theoretical notions of the tropical circulation, it was found that some of the observed characteristics could be explained in terms of an atmospheric response to tropical heat sources. The results suggest that seasonal changes were involved in the 1982 to 1983 El Nino collapse.