Interannual Variability Of Surface Sensible Heat Flux In The Tibetan Plateau And Its Impacts On The Advancing Process Of East-Asian Subtropical Summer Monsoon

Both East Asian Subtropical Monsoon (EASM) and Sensible Heat Flux in the Tibetan Plateau (SHFTP) are very important systems. This study investigates characterists of EASM and SHFTP and their possible relationship. First, the soaking rainfall index is defined to determine the EASM’s advancing process and the monthly SHFTP from 1982 to 2012 were calculated with the satellite remote sensing data and the observations from 70 meteorological stations. By comparing with 2 other data, and using some mathematical statistics, the basic climatic features of SHFTP are analyzed. Then, the surface heating Index (ISH) has been established, and some relationships between SHFTP and the advancing process of SHFTP have been found. The main conclusions are as follows:(1) EASM onset around mid to late march in Chiangnan area. SLP first inversed from winter to summer pattern in this latitude. Then progressive northward and arrived north boundary around mid to late July. EASM northward faster When onset later, and advancing northerly.(2) The Ch values have significant spatial and seasonal differences that high in east (summer) and low in west (winter), and then monthly SHFTP have been calculated by bulk transfer method, and compared with the existing data.(3) The interannual variation of SHFTP is mainly affected by the change of surface wind (V) in summer but the change of difference between surface temperature and air temperature (Ts-Ta) in winter. Due to the decreasing trend of V slowing down and the increasing of Ts-Ta, the interannual change of SHFTP has been transformed from decreasing to increasing around 2003. Then ISH index has been established based on four representative stations (Rikaze, Daocheng, Nangqian and Banma).(4) ISH has a good correlation with the advancement of EASM. The positive (negative) anomaly of ISH index in previous winter and spring indicate EASM onset later (early), but advancing faster (slower) and northerly (southerly). And stronge ISH index in spring may lead to the arrival of EASM early in northeast China region.