Droughts and Floods in South America Due to the 1982-83 El Nino-Southern Oscillation Episode

摘要

The 1982 to 83 El Nino/Southern Oscillation (ENSO) was one of the most intense ever recorded and it has affected the climate and weather in South America in several ways causing floods in many areas and droughts in others. Two aspects are concentrated on: (1) the abnormal dry period during January to February 1983 in central and northern Amazon and the severe drought over Northeast Brazil, from January through June, and (2) the extensive flooding in southern Brazil, northern Argentina and Paraguay in May to July 1983. Analysis of the 200 mb velocity potential charts from December 1982 to Feburary 1983 seems to indicate that the cause of that unusual dry spell was an anomalous Walker circulation. The extensive flooding in southern South America in May to July 1983 was caused primarily by excessive rainfall from a few quasi-stationary frontal systems.