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.