华北夏季降水异常与南太平洋夏季海表温度变化主要模态的可能联系

利用1951—2006年NCEP/NCAR再分析资料,采用EOF（empirical orthogonal function,经验正交函数）展开方法提取了南太平洋12—2月海表温度变化的主要模态,其第一模态反映了ENSO（El Nino-Southern Oscillation）的信号,周期为3～5a;第二模态与南半球环状模（Southern-Hemi-sphere annual mode,SAM）相联系,周期为准两年。结果表明,南太平洋EOF1时间序列处于正（负）相位时华北地区后期5月多（少）雨,同时注意到南、北太平洋EOF1对中国5月降水的影响区域基本一致。南太平洋EOF2时间序列处于正（负）相位时江南地区的夏季平均降水减少（增多）。去掉EOF1和EOF2的线性趋势后,这种显著相关仍然存在,只是显著相关区域有所缩小。利用南、北太平洋EOF1时间序列作为预报因子,建立回归预报方程,可为预测中国华北地区5月降水提供依据

Possible relationship between summer rainfall anomaly in North China and principal modes of SST variations over the South Pacific

The NCEP/NCAR reanalysis data have been used to check the principal modes of the South Pacific sea surface temperature（SST） anomalies through empirical orthogonal function（EOF） in DJF.The EOF1 mode of SST anomalies in the South Pacific is related to ENSO（El Nio-Southern Oscillation）and bears periodicities of 3—5 years.The EOF2 mode is related to Southern-Hemisphere Annual Mode（SAM） and bears the periodicities of quasi-biennial.The relationship between precipitation anomalies in China and the EOF modes of SST anomalies in the South Pacific is analyzed.When time coefficient of South Pacific EOF1 is in positive（negative） phase,the rainfall in May is more（less） than normal in North China.This scenario seems to be similar to that between rainfall and EOF1 mode of SST anomalies in the North Pacific.When the time coefficient of South Pacific EOF2 is in the positive（negative） phase,the rainfall of South China reduces（enhances） in summer.These results almost keep unchanged when the linear trend is removed separately from the SST anomalies and rainfall data.Using the time series of EOF1s of the South and North Pacific as two predictors,the rainfall in North China in May could probably be predicted