Possible mechanism of the effect of convection over Asian-Australian “land bridge” on the East Asian summer monsoon onset |
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| Authors: | He Jinhai Wen Min Ding Yihui and Zhang Renhe |
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| Institution: | (1) Jiangsu Key Laboratory of Meteorological Disaster (KLME), Nanjing Institute of Meteorology, Nanjing University of Information 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 |
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| Abstract: | 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. |
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| Keywords: | Asian-Australian “ land bridge” tropical convection Indo-China Peninsula the splitting of boreal subtropical high belt East Asian summer monsoon onset |
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