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A Study on the Mesoscale Convective Systems during the Summer Monsoon Onset over the South China Sea in 1998 Part II: Effect of Mesoscale Convective Systems on Large-Scale Fields
作者姓名:LIU Yanju  DING Yihui
作者单位:Institute of Atmospheric Physics,Chinese Academy of Sciences,National Climate Center Beijing 100029National Climate Center,Beijing 100081Graduate School of the Chinese Academy of Sciences,Beijing 100039,Beijing 100081
基金项目:Supported by the National Key Program: SCSMEX under Grant 98-monsoon-7-3.
摘    要:1. Introduction The strong convective weather is developed under the favorable large-scale circulations, which demon- strated the large-scale weather system's controlling ef- fect on strong convections. Once the convection is formed, it will produce the feedback effect on the large-scale environmental conditions by transporting momentum, heat and moisture upward, and influence or change the environmental wind, humidity, tem- perature, atmospheric stratification fields and so on, thus forming t…

收稿时间:2004/10/10 0:00:00
修稿时间:1/4/2005 12:00:00 AM

A Study on the Mesoscale Convective Systems during the Summer Monsoon Onset over the South China Sea in 1998 Part II: Effect of Mesoscale Convective Systems on Large-Scale Fields
LIU Yanju,DING Yihui.A Study on the Mesoscale Convective Systems during the Summer Monsoon Onset over the South China Sea in 1998 Part II: Effect of Mesoscale Convective Systems on Large-Scale Fields[J].Acta Meteorologica Sinica,2005,19(3):289-301.
Authors:LIU Yanju    and DING Yihui Institute of Atmospheric Physics  Chinese Academy of Sciences  Beijing National Climate Center  Beijing Graduate School of the Chinese Academy of Sciences  Beijing
Institution:LIU Yanju1,2,3 and DING Yihui2 1Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029 2 National Climate Center,Beijing 100081 3 Graduate School of the Chinese Academy of Sciences,Beijing 100039
Abstract: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 large- scale 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.
Keywords:mesoscale convection  apparent heat sources  apparent moisture sinks  feedback  
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