东亚夏季风成因的数值试验

NUMERICAL EXPERIMENTS ON THE FORMATION OF THE SUMMER MONSOON IN SOUTHEAST ASIA

本文应用中科院大气所二室设计的二层球谱模式,并引入 OSU 二层格点模式的物理过程,模拟了5月东亚夏季风的形成。通过四个试验的分析对比,揭示出:5月东亚季风的越赤道气流并不出现在105°E 附近,它位于45°—90°E 之间,但分析表明来自南半球的影响并不重要;海陆热力差异对低层西南风的形成起了一定的作用,但以地形的作用占主要,地形的动力作用在高原东南侧形成一个低压或槽,热力作用又使得它们加强并移近高原,于是形成了季风低压和季风槽。

A two-level spectral model of atmospheric circulation is adopted and the physics processes of the two-level atmospheric general circulation model of the OSU is introduced in this paper.In order to investigate the formation reason of the East Asia summer monsoon,four differentexperiments have been performed.By comparing and analysing of all these experiments,it revealsthat:(1)the diabatic heating distribution produces weak low-level southwestlies over the monsoonregion,(2)there is a mean across-equater airflow between the 45°-90°E,not in the vicinity of105°E and the analysis reveals that the affection of the south hemisphere is not important,(3)themountains have played very important role in the East Asia monsoon circulation.The mechanicaleffect produces a low or trough on the southeast side of the Plateau,then the thermodynamic ef-fect makes it strengthen and move close to the Plateau,thus the monsoon low or trough is formed.