The impact of land surface processes on the East Asian summer monsoon

[[abstract]]In this study, the land surface scheme of the Purdue Regional Model (PRM) was improved. Sun and Chern (2005) had created a new land surface model which had the ability of long term continue simulation to the Sleeper River region. In the new land surface model, including the vegetation, snow and soil parts. The land surface model was tried to improve the land surface process of the PRM. To evaluate the performance of the PRM was simulated to the 1998 East Asian summer monsoon case. The PRM can hold the well major features of the East Asian summer monsoon include the location of summer seasonal mean, the date of the summer onset, the northward propagation of the rain bands and ISOs. The simulated surface temperature is warmer than observed, and the Pacific subtropical high also is too strong. Due to the tropical high is too strong induce the precipitation is less in the south China and Indochina. The location of Mei-Yu front is more northward. The UMD and CNRM land use datasets are more high resolution what datasets were collected. In the vegetation scheme, the LAI data is used to modify the vegetation fraction. In the 1998 summer case, there are better results by using the CNRM dataset and observed LAI. The interaction process is complex between the land and atmosphere. For understand that the impact of land surface process, design some sensitivity test for land surface processes change, such as the warm and cold effect, different land cover and soil moisture cases. In these testes, the land sea heat contrast is more important than the local evaporation release to the influence of monsoon flow change. The precipitation is dominated by the monsoon flow. As the land surface temperature is warm, the monsoon flow is stronger than control run, induce the precipitation increase over East Asian. The monsoon flow is strong because is warm land case, induce the subtropical high decrease and withdraw eastward. One cyclone over Japan Sea is generated because monsoon flow is stronger. In the cold temperature case, the Pacific subtropical high increase and extend westward. The moisture flow of the summer monsoon moves westward, and induce the precipitation decrease over East Asia.