Interdecadal Changes Of Water Vapor Transport Source On East China Monsoon

Using air parcel tracking analysis method of Lagrangian (HYSPLITV4.9) and NCEP reanalysis data, Eastern China can be divided into four regions as Huanan, Jianghuai, Huaihe, Huabei Basin, according to the promotion of East Asian summer monsoon. This paper discusses the water vapor sources of precipitation and the contribution rates based on the analysis on climate scale and interdecadal characteristics of water vapor transport. The major results are as follows:(1) The water vapor of pre-flood season in South China mainly comes from three regions, they are the Indian Ocean, the Bay of Bengal-South China Sea and the Pacific Ocean, respectively with contribution rates of32%,32%and22%. From1950to2009, the water vapor transport contribution from the Indian Ocean region showed a decreasing trend, moisture transport contribution of Pacific was an increasing trend,moisture transport contribute of the Bay of Bengal-South China Sea less volatile.Water vapor transport contribution mutation began in1954.After mutation, water vapor transport contribution of the Indian Ocean region decreased from54%to30%, a decrease of24%;Moisture contribution of Pacific from26%to33%, an increase of7%;Water vapor contributions of the Bay of Bengal-the South China Sea, local and Eurasia have increased after1954, followed by an increase of3%,8%and5%.(2) The main water vapor sources of Jiangnan Meiyu Period is same as the Huanan Basin, with contribution rates of50%,22%and20%.Water vapor transport contribution of the Indian Ocean region and Eurasia region change significantly, Water vapor transport contribution of the Indian Ocean region showed a decreasing trend, moisture transport contribution of Eurasia showed an increasing trend.Water vapor transport contribution mutation began in1965.After mutation, water vapor transport contribution of the Indian Ocean region decreased from63%to45%, a decrease of18%; Eurasian water contribution from2%to7%, an increase of5%;Pacific water contribution from16%to20%, an increase of4%; Moisture contribution of the Bay of Bengal-South China Sea increased from18%to23%, an increase of5%;Local water vapor contribution increased from1%3%.(3) There exists four main regions of water vapor in the Huaihe Meiyu Period, which are the Indian Ocean, the Bay of Bengal-South China Sea, the Pacific Ocean and the Eurasian continent, accounting for42%,27%,17%and11%, respectively. From1950to2009, the water vapor transport contribution from the Indian Ocean region showed a decreasing trend, moisture transport contribution of Pacific and Eurasia was an increasing trend. Water vapor transport contribution mutation began in1968. After mutation, water vapor transport contribution of the Indian Ocean region decreased from61%to33%, a decrease of28%;Moisture contribution of Pacific from10%to18%, an increase of8%; Moisture contribution of Eurasia from3%to16%, an increase of13%; Moisture contribution of local increased from1%to6%, an increase of5%; Moisture contribution of Bay of Bengal-the South China Sea increased3%;(4) The water vapor during the rainy season of Huabei Basin mainly comes from five regions, which are the Indian Ocean, the Bay of Bengal-South China Sea, the Pacific Ocean, the Eurasian continent and local continent, accounting for25%,30%,14%,21%and10%. From1950to2009, water vapor contribution of Indian Ocean, Bay of Bengal-the South China Sea was a significant decreasing trend, water vapor contribution of Eurasia and local was a significant increasing trend. Water vapor transport contribution mutation began in1976. After mutation, water vapor transport contribution of the Indian Ocean region decreased from17%to5%, a decrease of12%; Moisture contribution of the Bay of Bengal-South China Sea decreased from34%to16%, an decrease of18%;Eurasia water vapor contribution increased from19%29%, an increase of19%; Local water vapor contribution increased from10%15%, an increase of5%; Small changes in water vapor contribute of Pacific.