平流层30 hPa月平均高度场的气候特征

采用经验正交函数分解(EOF)方法对NCEP／NCAR全球再分析资料中1958—1997年共40年,30hPa月平均高度和月平均风场进行了分析，讨论了40年平流层的主要特征向量和相应时间系数的变化特征，发现高度场的EOF第一模态具有很好的空间整体性和明显的季节变化。在平流层中，北半球冬季为一较大的环极冷低压，夏季为一以整个半球为规模的环极暖高压。并以1月和7月代表冬、夏季，选取1月和7月的40年资料作为时间序列，用EOF分析了冬、夏季不同的空问振荡型的特征，运用小波分析方法考察了其年际及年代际变化周期。并据此定义了不同的振荡型指数，为以后分析平流层要素场与气候变化的关系奠定了基础。

Climatic Characteristics of Monthly Mean Height Field on 30 hPa in Stratosphere

Using the monthly mean height and wind fields on 30 hPa of NCEP/NCAR reanalysis data from 1958 to 1997, the climatic characteristics in the stratosphere of Northern Hemisphere have been analyzed. The featuresof the various eigenvectors of the EOF and their corresponding time coefficients are discussed.It is found that the first EOF mode of height field has in-phase and evident variations. In the stratosphere of Northern Hemisphere, there is a circumpolar cold low in winter, and for a circumpolar warm high in summer. Taking January and July as the representations of winter and summer, the characteristics of different spatial oscillation patterns in winter and summer are analyzed by using EOF, and the periods of interannual and interdecadal changes are analyzed by using wavelet transfer. The oscillation indexes of the spatial patterns are defined and the climatic change in stratosphereis discussed.