南亚夏季风期间OLR的准40天振荡和准双周振荡

THE QUASI-40 DAY AND QUASI-BIWEEKLY OSCILLATIONS OF OLR DURING THE SOUTH ASIA SUMMER MONSOON

摘要:

文中采用时间域的带通滤波方法和合成分析技术,通过对1981年夏季月份OLR资料的准40天和准双周振荡的对比分析得到:(1)南亚季风区普遍存在准40天和准双周振荡,季风的活跃和中断要受其影响。(2)江淮流域到日本地区和南海到西太平洋地区OLR的分布是反位相的,它表明只有当南海季风槽断裂时,热带西南季风才能进入东亚大陆,这时大陆的季风雨较强。(3)OLR的分布表明,东亚大陆和印度北部平原季风雨的活跃与中断,对准40天振荡是同步的,而对准双周振荡是反位相的。(4)东亚大陆季风雨活跃与中断位相的转变,准40天振荡是从南海扰动中分裂出一块向北移动引起,而准双周振荡则是来自印度北部平原的季风扰动有规律的向东移动引起。

Abstract:

Using the band-pass filter and composite analysis in a temporal domain,quasi-40 day and quasi-biweekly oscillations for the OLR data in summer months of 1981 are compared to show that: (1) there are quasi-40 day and biweekly oscillations throughout the South Asia monsoon region, which affect the active/break of the monsoon ; (2) the OLR distribution from East China to the area of Japan is of opposite phase to that from the south China Sea to West Pacific, indicating that the tropical southwest monsoon will not move over the East Asia continent to bring there strong monsoon rain unless the monsoon trough breaks in the South China Sea; (3) OLR is so distributed that the active/break for the monsoon rain over the East Asia continent and the northern Indian plain is in phase with the quasi-40 day oscillation but of opposite phase to the quasi-biweekly oscillation ;and (4)the transition of the active/break for the monsoon rain in the East Asia continent and the quasi-40 day oscillaiton are caused by a northward-going part dissociated from a disturbance in the South China Sea, while the quasi-biweekly ossillation is resulted from regular eastward movement of the monsoon disturbance over the northern Indian plain.