中文摘要：

采用NCEP/NCAR逐日再分析资料,利用31点数字滤波器提取了58个冬季（1951/1952—2008/2009年）的500 hPa高度场低频分量,通过经验正交函数分析方法定义了6种低频环流型。从逐年低频环流型的差异和低频环流型系数两个角度分析低频环流型的年际变化特征;给出了58个冬季的主要低频环流型并分析了逐年低频环流型的变化特征;低频环流型系数的分析表明,Ⅰ型在20世纪90年代后振荡减弱,Ⅱ型表现为连续2 a为正（负）位相强年,Ⅲ型年代际变化明显,Ⅳ型在20世纪70年代到80年代之间年际振荡较强,Ⅴ型在20世纪80年代由正转负,Ⅵ型在20世纪70年代中期由负转正;低频环流型的显著周期大多出现在90年代之前。

英文摘要：

Based on the daily NCEP/NCAR reanalysis data,the 31-point low-pass filter was used to investigate the variation of atmospheric low frequency of 500 hPa height in winter in the Northern Hemisphere.By using the EOF analysis method,six leading EOF modes are defined six low frequency circulation patterns（LFCP） of 500 hPa geopotential height field.The interannual variation characteristics of LFCP are studied in view of the difference of the annual low frequency circulation and the low frequency circulation pattern index（LFCPI）.The paper presents the main LFCP of 58 winters（1951/1952—2008/2009） and analyses the characteristics of annual LFCP.The results show that the oscillation of Pattern Ⅰ decreases after 1990s,Pattern Ⅱ shows strong positive（negative） 2-years phase,Pattern Ⅲ has obvious interdecadal variation,Pattern Ⅳ behaves strong interannual oscillation between 1970s to 1980s,Pattern Ⅴ turns into negative phase from positive phase in 1980s,and Pattern Ⅵ changes into positive phase from negative phase in the mid-1970s.And the significant periods of LFCP mostly appear before 1990s.