SEASONAL TRANSITION OF EAST ASIAN SUBTROPICAL MONSOON AND ITS POSSIBLE MECHANISM  

作　　者：朱志伟 何金海 祁莉 

机构地区：[1]Jiangsu Key Laboratory of Meteorological Disaster,Nanjing University of Information Science and Technology

出　　处：《Journal of Tropical Meteorology》2012年第3期305-313,共9页热带气象学报（英文版）

基　　金：National Natural Science Foundation of China (41075068,40905044)

摘　　要：The NCEP/NCAR reanalysis datasets and Climate Prediction Center(CPC) Merged Analysis of Precipitation(CMAP) rain data are used to investigate the large scale seasonal transition of East Asian subtropical monsoon(EASM) and its possible mechanism.The key region of EASM is defined according to the seasonal transition feature of meridional wind.By combining the 'thermal wind' formula and the 'thermal adaptation' equation,a new 'thermal-wind-precipitation' relation is deduced.The area mean wind directions and thermal advections in different seasons are analyzed and it is shown that in summer(winter) monsoon period,the averaged wind direction in the EASM region varies clockwise(anticlockwise) with altitude,and the EASM region is dominated by warm(cold) advection.The seasonal transition of the wind direction at different levels and the corresponding meridional circulation consistently indicates that the subtropical summer monsoon is established between the end of March and the beginning of April.Finally,a conceptual schematic explanation for the mechanism of seasonal transition of EASM is proposed.The NCEP/NCAR reanalysis datasets and Climate Prediction Center （CPC） Merged Analysis of Precipitation （CMAP） rain data are used to investigate the large scale seasonal transition of East Asian subtropical monsoon （EASM） and its possible mechanism. The key region of EASM is defined according to the seasonal transition feature of meridional wind. By combining the ＇thermal wind＇ formula and the ＇thermal adaptation＇ equation, a new ＇thermal-wind-precipitation＇ relation is deduced. The area mean wind directions and thermal advections in different seasons are analyzed and it is shown that in summer （winter） monsoon period, the averaged wind direction in the EASM region varies clockwise （anticlockwise） with altitude, and the EASM region is dominated by warm （cold） advection. The seasonal transition of the wind direction at different levels and the corresponding meridional circulation consistently indicates that the subtropical summer monsoon is established between the end of March and the beginning of April. Finally, a conceptual schematic explanation for the mechanism of seasonal transition of EASM is proposed.

关 键 词：East Asian Subtropical Monsoon seasonal transition MECHANISM 

分 类 号：P462.4[天文地球—大气科学及气象学]