中文摘要：

基于CORA再分析资料对南海环流的季节特征和其受ElNino事件的响应进行了分析。结果表明，冬季整个南海海区表现为一个大的气旋式环流，夏季南海北部是气旋式环流，南部是一个反气旋式环流。通过对南海海区异常流场进行MV-EOF分解，分析其前两个模态，其空间型主要体现了南海环流冬季和夏季的特征，对应的时间系数与ElNino3.4_4NDJ指数有很好的相关性。通过分析南海环流在1986--2008年间ElNino年份的异常流场和异常流函数场，证明了MV-EOF分解后得到的联合时间系数所反映各阶段南海环流的季节特征与ElNino事件有相关性，即在8月[0]，南海南部异常流函数场表现为反气旋式环流，北部为气旋式环流，南海夏季环流被增强，且ElNino事件时间尺度越长，北部的气旋式异常流场的影响范围就越大；在12月[0]，南海除了东南部外，其余整个海区异常流函数场主要表现为反气旋式环流，冬季环流被减弱；在8月[＋1]，南海夏季流场强度都被削弱了。

英文摘要：

Based on the CORA （China Ocean ReAnalysis） data sets, we analyze the seasonal characteristics of the cir- culation in the South China Sea （SCS） and its response to ElNino. 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 ElNino3.4 index. By analyzing the current and stream function anomaly during the ElNino events from 1986 to 2008, we find that the circulation changes during the different stages of the E1 Nifio. 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 back-ground summer circulation. The northern cyclonic circulation anomaly becomes larger as ElNino 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.