Inter-annual Change Of East Asian Summer Monsoon And Simulating Analysis Of BCC_CSM

This paper firstly studied the process of East Asian Summer Monsoon activity in the year of 2007, and analyzed its influence on the precipitation of Yangtze-Huaihe Region. Then we calculated East Asian summer monsoon index (EASMI) for 50 years, studying the inter-annual change of East Asian Summer Monsoon as well as its association with general circulation over East Asian and precipitation of Meiyu front area. At last, characteristics of East Asian Summer Monsoon activity and its inter-annual variability were studied by numerical simulation and the simulating results of BCC_CSM had been checked and assessed. The work of this dissertation can be summarized in the following parts:(1) In the year of 2007, South China Sea Summer Monsoon broke out at 29th pentad, which indicated the beginning of East Asian Summer Monsoon activity. At the same time, both meridional temperature difference and wind shear of Mid-Low Latitudes had changed. After that, southwest flow moved eastward and northward, transporting moisture to the Yangtze and Huaihe River basins as well as south china, which was in favor of rain occurrence.(2) In the process of East Asian Summer Monsoon activity, general circulation was anomalous in the Meiyu period. There existed blocking high over high latitude of 500hPa at the beginning of meiyu event in 2007.During the meiyu period, the ridgeline of west Pacific subtropical high was on the south side and the activity of Monsoon Surge lasted for a long time. The southwest flow near Meiyu front was strong, transporting the vapor from monsoon trough to the Yangtze-Huaihe Region continuously, which caused flood disaster that only weaker than 1954 over the Huaihe basin.(3)When EASMI looked stronger, the west pacific subtropical high lay more northward and the intensity of meiyu front was weaker, meanwhile, rainfall of meiyu front over Yangtze River basin was less than normal years. On the contrary, when EASMI looked weaker, the west pacific subtropical high lay more southward and the intensity of meiyu front was stronger, rainfall of meiyu front over Yangtze River basin was more than normal years.(4)The coupled climate system model BCC_CSM1.0.1 is developed by National Climate Center. Using its output data to calculate East Asian summer monsoon index then check it, the results showed that whether EASMI was higher or lower, the precipitation of Meiyu front area could be simulated pretty well by this model. But the simulated anomalous precipitation was relative low, and some of the positive and negative zone didn't come out. So it is necessary to rectify the physical process of the model in order to improve its simulating ability.