The Differences and sames of vapor transportation between strong vapor transportation year and weak one in the East-Asia

By use of the NCEP/NCAR daily mean reanalysis data from 1950 to 2002, vertically integrated moisture fluxes (VIMFs) were calculated over East Asia, and a strong/weak moisture transport year (SMTY/WMTY) was defined according the coefficient of the first EEOF eigenvector of pentad mean VIMFs of the summer half-year (April-September) for the period 1950-2002. Similarities and differences of pentad mean VIMFs between SMTYs and WMTYs are studied through examination of the spatial distributions of mean moisture transport, seasonal advance of southerly wind moisture transport (SMT), and the intensity and evolution of the southeast wind moisture transport (SEMT) south of the Northwest Pacific subtropical high. The results show that:1) In SMTYs, the northward transport of VIMFs across the Equator from the Southern Hemisphere to the Northern Hemisphere, and the northeastward transport of VIMFs over the Arab Sea and the Bay of Bengal are significntly large, the westerly wind moisture transport belt in the mid-latitudes (40°-45°N) over East Asia is remarkable, and changes in moisture transport in the summer half-year are relatively small. However, in WMTYs, the opposite is true. Furthermore, there is a large VIMF belt over the Yunnan-Guizhou Plateau, the midreach of the Yangtze River, North China, and the southern part of Northeast China in SMTYs, but in WMTYs, there is only a small VIMFs belt over southern China,the east coast region, and the southern part of Northeast China. 2) The SMT in East Asia (100°-130°E) starts earlier in SMTYs, it reaches a higher latitude and prevails for a longer period of time, and retreats southwards at a later date in comparison with that in WMTYs. 3) The onset of SEMT at 160°E in SMTYs is earlier, the SEMT lasts longer, and reaches its western limit (95°E) later relative to the transport in WMTYs; and the SEMT west of 95°E in the south of Himalaya Mountains associated with the Indian monsoon trough has a longer duration and a larger influencing region in SMTYs than in WMTYs.