Effects of surface heating over Indochina and India landmasses on the summer monsoon over South China

Sensitivity experiments have been performed using a regional climate model to study the effect of land-surface heating over the Indochina and Indian Peninsulas on the summer monsoon over South China. The term surface heating is defined here as the sum of sensible heat flux and net flux of longwave radiation from the surface. In each sensitivity experiment, the surface heating over the land surface of the region considered is cut off, but evaporation over the land surface and latent heat release are still permitted. Compared with that of the Indian Peninsula, surface heating over the Indochina Peninsula has a much more significant effect on both the monsoon circulation and precipitation over South China and the East Asia regions, particularly during the onset period of the summer monsoon over South China. The effect of this surface heating on the vertical velocity over Indochina extends much deeper into the upper troposphere. Precipitation is reduced significantly not only locally, but also extends to South China, as well as the remote regions of East China and the western North Pacific. The variations in geopotential height fields in the lower troposphere and the zonal wind field in the upper troposphere suggest that the surface heating over Indochina may have an important effect on the strength of the subtropical high, and is closely related to the onset of the South China Sea summer monsoon. On the other hand, the surface-heating effect of the Indian Peninsula on precipitation as well as the monsoon circulation is found to be relatively local and mainly affects the Bay of Bengal region. Copyright (C) 2006 Royal Meteorological Society.