东亚夏季风的低频振荡及其与500hPa角动量输送变化的关系

LOW-FREQUENCY OSCILLATION OF SUMMER MON-SOON IN EAST ASIA AND ITS RELATION WITH THE TRANSPORT OF ANGULAR MOMENTUM AT 500hPa

摘要:

本文用谱分析和经验正交函数分析了1986年夏季风时期亚洲高空越赤道气流和低空赤道西风的低频振荡特征。高低空两支季风气流的30—50天滤波序列的主要经验正交函数能较好地反映亚洲夏季风低频振荡的空间特征。根据EOF1时间序列的振荡位相可以确定东亚夏季风活跃/中断的具体时间。后延相关揭示出北半球500hPa中低纬角动量输送的经向交换同东亚夏季风的低频活动有密切关系。

Abstract:

Based on spectral analysis and EOFs,the characteristics of low frequency oscillation are studied for the upper cross-equatorial flow and lower equato-rial westerly during 1986 Asian summer monsoon. The main EOFs in the filter series for the two monsoon flows well represent the spatial characteristics of the oscillation. The phase of the time series of EOFs determines the specific time for the active/break periods of the summer monsoon in East Asia. The lag correlation reveals a close relation of the meridional exchange in the 500 hPa transfer of angular momentum in the northern mid-and-low latitudes to the low frequency activity of the summer monsoon in East Asia.