A Diagnostic Study of Water Vapor Transport and Budget during Heavy Precipitation over the Huaihe River Basin in 2007

By using the NCAR/NCEP reanalysis data and the HYSPLITv4.9 mode, the variation features of the water vapor transportation and the contribution of vapor for major passages are analyzed during the heavy precipitation over the Huaihe River basin from 19 June to 26 July in 2007 which is divided into three stages. The results show that there are three major vapor inflow corridors to the Huaihe River basin．One of them is the southeast flow around the western Pacific subtropical high, another is northward vapor transport from cross-equatorial flow in the southern South China Sea, the last is from Somali jet via the Arabian Sea and the northern Bay of Bengal．During the first stage, the transportation of vapor originating from the western Pacific is most important and accounts for 69% of the total transportation. During the second and third stages, the cross-equatorial flow in the southern South China Sea is dominant and accounts for 52% and 57% of total moisture transportation, respectively．Somali jet via the Bay of Bengal transports moisture to the levels above 750 hPa, and the South China Sea and the subtropical high moisture transports to the levels under 850hPa.