东亚夏季风准40天振荡的垂直结构

THE VERTICAL STRUCTURE OF QUASI-40 DAY OSCILLATION OF EAST ASIAN SUMMER MONSOON

水文分析了1981年6—9月风场和温压场资料,发现各物理量都存在明显的准40天周期振荡,其振幅在200百帕上表现最为明显。结果表明中纬度和低纬度地区低频振荡的垂直结构和机制不同。振荡系统在中纬度地区表观为准正压结构,而在低纬地区具有明显的位相向上传播特征,其传播速度大约为300百帕/10天。指出了西风带的长波调整和东亚两支东风急流强度的变化与准40天振荡具有密切关系。

Based on wind, temperature and geopotential height data from July to September 1981, we find that there is a quasi-40 day oscillation in each field, the amplitude is much obvious in 200 hPa. The vertical structures and mechanism of low frequency fluctuation are different in midlatitude and tropic. Low frequency change shows quasi-barotropic character in midlatitude and has clear upward propagation with the velocity about 300 hPa per ten days in tropic. This paper points out that there is close relationship between Low frequency oscillation and long-wave adjustment process in westerly belt and the variation of two easterly jets in east Asian as well.