Analysis On An Application Of Air Parcel Tracking Analysis Method Of Lagrangian In The Study Of Water Vapor Tranport

Using NCEP reanalysis data and the airflow trajectory model based on lagrangian method （HYSPLIT₄.9）, water vapor transport in weather and climate scale have been discussed in this paper. The simulation of air flow3-Dimension trajectories in the research region discuss the source of precipitation and the contribution rates of vapor of various regions. The application on the method of Lagrange trajectory in this article mainly focus on three conclusions:Firstly, the method of Lagrange trajectory is employed to perform diagnostic analyses on the water vapor transportation characteristics over Yangtze valley in1998, The results showed that the water vapor of summer rainfall in Yangtze River Basin mainly come from five regions, they are the Bay of Bengal-South China Sea, Indian Ocean, the Pacific region, the Eurasian continent and local continent. Further calculation the contribution rates of vapor, we find that during the first and three stages, the moisture of Yangtze valley mainly come from the Bay of Bengal-South China Sea, Indian Ocean, the Eurasian continent and local continent. Among of them, the vapor originate from the Bay of Bengal-South China Sea and Indian Ocean is account for65%of the total moisture transport and the vapor originate from the Eurasian continent and local continent is15%of the total moisture transport respectively, during the two and four stages the moisture of Yangtze valley mainly come from the Bay of Bengal-South China Sea, Indian Ocean, the Pacific region, accounting for65%and25%of the total moisture transport respectively.Secondly the method of Lagrange trajectory is employed to perform diagnostic analyses on the climatological characteristics of water vapor over Yangtze-Huaihe valley, The results showed that the water vapor of summer rainfall mainly come from Indian Ocean, the Bay of Bengal-South China Sea, the Pacific Ocean, the Eurasian continent, and local continent, accounting for29%,19%,28%,18%and5%of the total moisture transport respectively. In addition, by comparing the characteristics of hou evolution of water vapor sources, we found that water vapor sources of summer rainfall experience three changes:<1>60%water vapor is transported by westerly flow of high-latitude, from1hou to3hou in June,<2> the contribution rates of water vapor coming from tropical regions is80%, from5hou of June to5hou of july,<3> After5hou of july, water vapor coming from hight-latitude gradually become important, The the contribution rates of it is52%.Thirdly the method of Lagrange trajectory is employed to perform diagnostic analyses on the climatological characteristics of water vapor transport of Meiyu and its differences in the abnormal years, The results showed that the water vapor of Meiyu mainly come from the Bay of Bengal-South China Sea, Indian Ocean, the Pacific Ocean and the Eurasian continent, accounting for19%,35%,22%and19%of the total moisture transport respectively. Among of them, the water vapor of Indian Ocean, the Bay of Bengal-South China Sea and the Pacific Ocean are from lower troposphere where is under the850hPa, while the water vapor of Eurasian continent comes from the middle troposphere. Besides, by comparing the differences of Meiyu in abnormal years, we found that water vapor which is from the bay of Bengal-South China Sea, India ocean, and the Pacific region have import influences on the anomalies of Meiyu. In wet Meiyu years, water vapor coming from the bay of Bengal-South China Sea is more13%than that in dry Meiyu years, reaching to24%, but for the areas of Pacific and India Ocean in dry years, the contribution rates of water vapor are40%and30%respectively.