中文摘要：

采用诊断方法研究了E1 Nino和La Nina事件与北半球中高纬大气低频振荡。用1950—2003年北半球中高纬逐日500hPa高度场资料进行功率谱分析得出：（1）ENSO事件对中高纬大气低频振荡有调频作用，即夏季低频振荡较弱，冬季低频振荡较强。（2）E1 Nino（La Nina）事件有使低频振荡周期缩短（延长）的趋势。（3）ENSO事件对中高纬大气低频振荡的调频作用比中低纬明显。

英文摘要：

A diagnostic analysis is carded out to investigate the relationship of ENSO episodes and the atmospheric low-frequency oscillation （LFO） in the mid-high latitudes of the Northern Hemisphere. The power spectral analysis is performed for the daily 500 hPa height field data in the mid-high latitudes of the Northern Hemisphere from 1950 to 2003. The results show that： （1） ENSO episodes have the frequency modulation effect on low-frequency oscillation （LFO） in the extra-tropical latitudes of the Northern Hemisphere, i.e. Intensity of low-frequency oscillation in winter is stronger than that in summer. （2） The main period of low-frequency oscillation show the shortened （lengthened） tendency during E1 Nino （La Nina） episodes. （3） The frequency modulation effect of ENSO episodes on atmospheric low-frequency oscillation （LFO） in the mid-high latitudes is clearer than that in the mid-low latitudes.