A Study on the Mesoscale Convective Systems during the Summer Monsoon Onset over the South China Sea in 1998 Part Ⅱ: Eff
The apparent heat sources and apparent moisture sinks, and large-scale wind, temperature as well as the surface pressure fields during the summer monsoon onset over the northern South China Sea (SCS) in 1998 were diagnosed. The results suggested that there was a kind of positive feedback mechanism between large-scale circulations and mesoscale convective systems (MCSs). Before the monsoon onset, the largescale background provided favorable synoptic and dynamic conditions for the summer monsoon onset and the formation of mesoscale convective activities, whereas after the summer monsoon onset, occurrence of the persistent and extensive mesoscale convective activities produced obvious feedback effect on large-scale circulations. Because of the release of latent heating produced by enhanced convective activities, the intense atmospheric heating appeared over the northern SCS, which resulted in: (1) the meridional temperature gradient over the SCS reversed from upper-level to low-level and then the large-scale circulations were changed seasonally;(2) correspondingly, the surface pressure over the northern SCS deepened continually and formed a broad monsoon trough and the obvious pressure-fall areas, thus making the subtropical high move out of the SCS eventually;(3) with the development of the low pressure circulations in the middle and low troposphere, the MCSs further enhanced and extended southward, which was conducive to the SCS monsoon onset and maintenance over the middle and southern SCS;and (4) the deepening of monsoon trough facilitated the monsoon flow and moisture transport on its southern side, thus the monsoon onset reaching peak period.
作 者： LIU Yanju DING Yihui 作者单位： LIU Yanju(Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;National Climate Center, Beijing 100081;Graduate School of the Chinese Academy of Sciences, Beijing 100039)DING Yihui(National Climate Center, Beijing 100081)
刊 名： 气象学报（英文版） SCI 英文刊名： ACTA METEOROLOGICA SINICA 年，卷(期)： 2005 19(3) 分类号： P4 关键词： mesoscale convection apparent heat sources apparent moisture sinks feedback