Analysis of water vapor transport characteristics during the Vleiyu over the Yangtze-Huaihe River valley using the Lagrangian method

Using the NCEP reanalysis data and the airflow trajectory model based on the Lagrangian method(HYSPLT_4.9).the climatological characteristics of water vapor transport associated with the Meiyu and its differences in the abnormal years have been discussed in this paper. The results showed that the water vapor of the Meiyu mainly come from the Bay of Bengal-South China Sea. the Indian Ocean.the Pacific region and the Eurasian continent.accounting for 19%, 35%, 22% and 19% of the total moisture transport, respectively. Among of them, the water vapor over the Indian Ocean,the Bay of Bengal-South China Sea and the Pacific Ocean are from the lower troposphere under the 850 hPa, while the water vapor over the Eurasian continent comes from the middle troposphere. Besides, by comparing with the differences in the abnormal years, we found that water vapors from the Fray of Bengal-South China Sea, the India Ocean, and the Pacific region have import influences on the Meiyu anomalies. In wet Meiyu years, water vapor coming from the Bay of Bengal-South China Sea is more by 13% than that in dry Meiyu years, reaching to 24%, but for the areas of the Pacific and India Oceans in dry years, the contribution rates of water vapor are 40% and 30% respectively.