资源环境科技发展态势分析平台

The origin of the East Asian summer monsoon (EASM)-the sole monsoon existing in the subtropics-midlatitude in the northern hemisphere-has long been recognized as an elevated heating and mechanical forcing of the Tibetan Plateau, and the land-sea zonal heat contrast. However, the relative contribution of individual processes to the generation of the East Asian summer monsoon and therefore the underlying basic physics are unexplored. Here we show that the EASM is mainly driven by the dynamical effect of the Tibetan Plateau, in which forced topographic Rossby waves induce downstream southerlies, a crucial factor in EASM precipitation. From idealized general circulation model simulations, the dynamical effect of mountains is revealed to account for similar to 65% of the total East Asian summer precipitation, whereas the elevated heating and land-sea heat contrast are only responsible for similar to 15% each and the mountain-drag effect accounts for less than 5%.