Possible mechanism of the effect of convection over Asian-Australian “land bridge” on the East Asian summer monsoon onset  

作　　者：HE Jinhai1, WEN Min2, DING Yihui3 & ZHANG Renhe2 1. Jiangsu Key Laboratory of Meteorological Disaster (KLME), Nanjing Institute of Meteorology, Nanjing University of Informa- tion Science and Technology, Nanjing 210044, China 2. State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorological Sciences, Beijing 100081, China 3. National Climate Center, Chinese Meteorological Administration, Beijing 100081, China 

出　　处：《Science China Earth Sciences》2006年第11期1223-1232,共10页中国科学（地球科学英文版）

基　　金：This work was supported by the National Natural Science Foundation of China(Grant Nos.40305005 and 40225012);the National Key Program for Developing Basic Sciences(Grant No.2004CB418302).

摘　　要：The Asian-Australian “land bridge” is an area with the most vigorous convection in Asian monsoon region in boreal spring, where the onset and march of convection are well associated with the onset of East Asian summer monsoon. The convection occurs over Indo-China Peninsula as early as mid-April, which exerts critical impact on the evolution of monsoon circulation. Before mid-April there are primarily sensible heatings to the atmosphere over Indo-China Peninsula and Indian Peninsula, so the apparent heating ratios over them decrease with height. However, after mid-April it changes into latent heating over Indo-China Peninsula due to the onset of convection, and the apparent heating ratio increases with height in mid- and lower troposphere. The vertical distribution of heating ratio and its differences between Indo-China Peninsula and Indian Peninsula are the key factors leading to the splitting of boreal subtropical high belt over the Bay of Bengal. Such mechanism is strongly supported by the fact that the evolution of the vertical heating ratio gradient above Indo-China Peninsula leads that of 850 hPa vorticity over the Bay of Bengal. Convections over Indo-China Peninsula and its surrounding areas further increase after the splitting. Since then, there is a positive feedback lying among the convective heating, the eastward retreat of the subtropical high and the march of monsoon, which is a possible mechanism of the advance of summer monsoon and convection from Indo-China Peninsula to South China Sea.The Asian-Australian 'land bridge' is an area with the most vigorousconvection in Asian monsoon region in boreal spring, where the onset and march of convection arewell associated with the onset of East Asian summer monsoon. The convection occurs over Indo-ChinaPeninsula as early as mid-April, which exerts critical impact on the evolution of monsooncirculation. Before mid-April there are primarily sensible heatings to the atmosphere overIndo-China Peninsula and Indian Peninsula, so the apparent heating ratios over them decrease withheight. However, after mid-April it changes into latent heating over Indo-China Peninsula due to theonset of convection, and the apparent heating ratio increases with height in mid- and lowertroposphere. The vertical distribution of heating ratio and its differences between Indo-ChinaPeninsula and Indian Peninsula are the key factors leading to the splitting of boreal subtropicalhigh belt over the Bay of Bengal. Such mechanism is strongly supported by the fact that theevolution of the vertical heating ratio gradient above Indo-China Peninsula leads that of 850 hPavorticity over the Bay of Bengal. Convections over Indo-China Peninsula and its surrounding areasfurther increase after the splitting. Since then, there is a positive feedback lying among theconvective heating, the eastward retreat of the subtropical high and the march of monsoon, which isa possible mechanism of the advance of summer monsoon and convection from Indo-China Peninsula toSouth China Sea.

关 键 词：Asian-Australian 'land bridge'  tropical convection  Indo-China Peninsula  the splitting of BOREAL SUBTROPICAL high belt  East ASIAN summer MONSOON onset. 

分 类 号：P425.42[天文地球—大气科学及气象学]