南方涛动指数的多元统计分析及其与北半球500hPa月平均环流的关系

本文对美国的CAC南方涛动指数进行了相关分析、因子分析、模糊聚类、主成份分析。指出,月指数可分为二组:1—4月,5—12月,它们的持续性和相关性不相同。还指出,强弱南方涛动可以用涛动指数的第一主成份来定义。 此外,用1951—1984年的月资料讨论了南方涛动指数与当年1月到来年12月的500hPa位势高度场、月平均纬圈高度、月平均纬际高度差、大气活动中心以及大气环流特征量的相互关系。分析表明,在涛动低值年的前期4月份75°N以北的500hPa位势高度明显偏低,5月份偏高;低值年4月第一谐波槽位于东半球并且方差贡献小,5月份一波槽方差贡献大,高值年相反。500hPa位势高度在4—5月的这种变化是涛动在高纬度的一个早期讯号。 最后,我们建立了一个涛动指数的统计预报模式。利用这个模式可成功地预报出1986年的弱涛动并发生El Nino现象。

A MULTI-STATISTICAL ANALYSIS OF THE SOUTHERN OSCILLATION (SO) AND ITS RELATION TO THE MEAN MONTHLY ATMOSPHERIC CIRCULATION AT 500 hPa IN THE NORTHERN HEMISPHERE

In this paper the correlation analysis,factor analysis,fuzzy classification.,and principal component analysis (PCA) are performed for the southern osciliation index (SOI) from the Ciimate Analysis Center (CAC) at the NOAH.It is shown that the 12-month SOI can be classified into two groups:one from January through April and the other from May through December.They differ in persistency and correlation.It is also found that the year of strong or weak SO can be defined by the first principal component of the SOI.In addition.the relations beiwaen the SOI and 50p hPa geopotential height,mean monthly zonal height,mean monthly interzonal height differences,centers of atmospheric activities,characteristics of the atmospheric circulation int period of 24 months from January through December of the neat year have been.examinated based on the monthly data from 1951 t hrough 1984.Analysis indicates that in the early part of the low SOI year,i.e.,in April,the 500 hPa geopotential height north of 75°N is significantly low and then becomes higher in May.It is found that in April the trough of the first harmonic wave is in the eastern hemisphere and the contribution of its variance is smaller than in May.Analysis shows that the opposite is true in the high SOI year.Such variation in the height field during the April-May period is an early signal of the SO at higher latitudes.In the end,a statistical prediction model for the SOI is presented,by means of which a low SOI year as well as an E1 Nino event has been successfully predicted for 1986.