ANOMALOUS CHARACTERISTICS OF THE OCEAN CIRCULATION IN SOUTH CHINA SEA DURING THE El NIO EVENTS
El Nio事件期间南海环流的异常特征

Based on the CORA(China Ocean ReAnalysis) data sets,we analyze the seasonal characteristics of the circulation in the South China Sea(SCS) and its response to El Nio.The winter circulation in the SCS is overall cyclonic.The summer circulation can be divided into two parts,cyclonic in the north and anti-cyclonic in the south.We analyze the circulation anomalies in the SCS using the MV-EOF method.The first and second space modes of the circulation represent winter and summer circulation,respectively.The corresponding temporal coefficients have clear relationship with the Nio3.4 index.By analyzing the current and stream function anomaly during the El Nio events from 1986 to 2008,we find that the circulation changes during the different stages of the El Nio.In August,the stream function anomaly shows an anti-cyclonic circulation in the southern SCS and a cyclonic circulation in the northern part,strengthening the background summer circulation.The northern cyclonic circulation anomaly becomes larger as El Nio event goes on.By December,anti-cyclonic circulation anomalies prevail in the whole SCS except for the southeastern region,weakening the background winter circulation.In next August the circulations in the SCS were obviously weakened.