Effect of the Tibetan Plateau on the East Asian Monsoon Circulations: A Regional Climate Model Study

It is well known that the Tibetan Plateau (TP) has great influence on the East Asian summer monsoon, as a primary heat source of the Tibetan High. In order to identify the effect of TP upon the East Asian summer monsoon, simulations are performed by using a Regional Spectral Model (RSM). These consist of nine different experiments depending on height variation of TP from 0% to 140%, and in these experiments, the land-sea distribution is prescribed same. These simulations are conducted during boreal summer of 2004, which the Korean peninsula has experienced much heavy rainfall and warmer than normal year. The simulations with the lower height of TP tend to force expansion of the North Pacific high but weaken of middle latitude jet flow in June and July. Therefore, Chang-ma is not well-simulated in the Korean Peninsula in June and July, but Mei-Yu and Baiu are well-simulated in the China and Japan in June. Also, in August it is shown that jet flow move to high latitude, whereas the cyclonic circulation is strengthened over the south China and India. It results in the change in the wind direction from ocean to continent over southeast China. Otherwise, the experiments with higher TP show that the moisture transport in the lower troposphere over the India region below 30°N tends to become stronger, which causes more precipitation over the East Asian region. Additionally, the simulations with higher TP result shows strengthen of precipitation over the south China in August, due to the strengthened the Tibetan High. The variation experiments with height of the TP show that precipitation over the Korea on June increase. But the precipitation decrease on July and August. Incase of the South China, the results reverse. In summery, variation of height of TP has a big change of the East Asian Monsoon intensification and timing due to generation of the change in large-scale circulation.