Role of Land-Atmosphere Interaction on Asian Monsoon Climate

Abstract

This paper has discussed the land-atmosphere interaction associated with the Asian monsoon climate and its variability. The snow cover and soil moisture are internal factors of the climate system panicularly in the seasonal to interannual time scales, but are suggested to play some important roles in changing large-scale surface energy and water balance, which in turn affect the monsoon circulation and precipitation. From the modeling as well as observational studies it has been suggested that the snow cover is most likely to influence atmosphere essentially through the albedo effect particularly in lower latitudes and on the Tibetan Plateau. The GCM experiments have strongly suggested that soil moisture anomalies efficiently affect the atmosphere under dry or semi-arid condition. Vegetation has also been noted as an important variable for the formation of moist monsoon flow over the continent, in addition to the dynamical and thermo-dynamical effect of the Tibetan Plateau.
Through the GCM and RCM experiments the anthropogenically-induced change of land coverluse including the deforestation has proved to be a great impact on regional precipitation and water cycle of the monsoon region by changing characteristics of vegetation control in energy and water cycle, which in turn affect atmospheric boundary layer (ABL) and cloud/precipitation processes in regional-scale. The discussion has also been made on how the land surface changes could induce change of precipitation through feedback processes of moisture convergence and in-situ evapo-transpiration processes. The critical role of moisture amount near surface and in the ABL is emphasized, to induce positive feedback to change of precipitation over land in the monsoon region.