Dynamical Control of the Tibetan Plateau on the East Asian Summer Monsoon

During summer monsoon period, long term precipitation and southerly wind appears over the East Asia. The East Asian summer monsoon has long been recognized as a response to the elevated heating and mechanical effects of the Tibetan plateau, and the land–sea zonal heat contrast. However, the relative contribution of individual process to the East Asian summer monsoon generation and the underlying basic dynamics are not elucidated. As a predominant mechanism of the EASM, we stress the fluid dynamical effect of the Tibetan plateau, which is related to the forced topographic barotropic Rossby waves based on the potential vorticity conservation theory. The theoretical prediction of mid-latitude geopotential height is calculated by a function of zonal wind velocity above the Tibetan plateau. Theoretical derivations of the pressure gradient, meridional wind and precipitation over the East Asian summer monsoon area are all closely following the observations. In idealized GCM simulations, the rainfall forced by dynamical effect of mountain occupies most of the total East Asian precipitation. Our results highlight that the southerly wind caused by mid-latitude jet stream on the Tibetan plateau mainly generate the East Asian summer monsoon through the fluid dynamics. It can be used as a metric to evaluate the performance of GCM simulation and contribute to skillful prediction of the East Asian summer climate. In addition, this study provides a scientific cornerstone for developing theoretical framework.