The Fearures of the Wintertime Stratospheric Atmospheric Low-Frequency Oscillation in the Northern Hemisphere
北半球冬半年平流层大气低频振荡特征的研究

Based on the NCEP/NCAR reanalysis data(geopotential height field and wind field data from 1970 to 1999),the dominant period of the low-frequency oscillation in the wintertime stratospheric atmosphere of the Northern Hemisphere is examined distinctly by using morlet wave analysis.In the wintertime stratospheric atmosphere of the Northern Hemisphere,the vertical structure,the direction of the horizontal propagation and the most active areas of the low-frequency oscillation are related in detail.At last the spatial patterns of the low-frequency oscillation are also showed in the paper. By using the daily data at many levels,the wavelet analysis suggests that there is a remarkable low-frequency oscillation(a dominant period of 60 days) existing in the wintertime stratospheric atmosphere of the Northern Hemisphere.By the way,the results show that there is another period of 20 days,but the period of 60 days is more distinct.So the period of the band-pass filter in the text is 15 to 90 days.The low-frequency oscillation has a barotropic structure on the vertical plane and a westward propagation on the horizontal plane by using the daily data at many levels.And the Arctic oscillation(AO) is in particular dominant,three active centers are located in the Eurasia,the northern Pacific,the northern Atlantic. Results show the spatial patterns of the low-frequency oscillation by using the singular value decomposition(SVD) of the geopotential height fields at many levels.The leading mode is AO.By calculating the correlation coefficients of the geopotential height fields at many levels,the figures show the same result as the figures of SVD.In the wintertime stratospheric atmosphere of the Northern Hemisphere,there exists the negative correlation between AO and the other fields.And the figures also show some characters of PNA(Pacific-North American Pattern) and EUP(Eurasia-Pacific Pattern) in the stratospheric atmosphere of the Northern Hemisphere.Compared with those of the troposphere atmosphere,the spatial structure,propagation and regional distribution of the low frequency oscillation of the stratospheric atmosphere are different but related.