北半球冬半年平流层大气低频振荡特征的研究

利用NCEP/NCAR(1970～1999年)位势高度场和风场再分析资料,通过小波分析的方法,研究并揭示了北半球冬半年平流层大气低频振荡的周期,然后通过滤波等方法,揭示了冬半年平流层大气低频振荡的空间结构、传播规律、地域分布特征及北半球低频遥相关的一些分布特征,并且与对流层大气低频振荡作比较.作者对北半球平流层大气低频振荡进行的系统分析研究结果表明:在北半球冬半年平流层,大气低频振荡十分显著,其振荡周期以60天最为显著,在垂直方向上表现出正压结构特征,在水平方向上表现为一致西传,并且以北极涛动(the arctic oscillation)占据主导地位.北半球冬半年平流层大气低频振荡主要活动区域为北极地区,并且在45°N附近还存在3个活动中心,即欧亚大陆、北太平洋和北大西洋中心.

The Fearures of the Wintertime Stratospheric Atmospheric Low-Frequency Oscillation in the Northern Hemisphere

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.