Relationship Between Characteristics Of Perturbation & Average Water Vapor Transport In Asian-Australian Moonsoon Area And Jianghuai Meiyu Anomaly

Using the daily NCEP/NCAR reanalysis dataset for the period from1957～2001, the monthly water vapor transportation in the total atmosphere wasintegrated from the earth's surface to the top layer. The perturbation water vaportransport is defined as the difference between the monthly moisture transportationand its mean value. Several characteristics of seasonal variation of water vaportransport in Changjiang-Huaihe River Basin were obtained by analyzing theaverage and perturbation water vapor transport. The differences between averageand perturbation water vapor transportation in drought and flood years in JianghuaiMeiyu period were also investigated. A few conclusions are as follows:(1) The average water vapor transport in Jiang-huai Basin is mainly from theeastward flows in the middle-low latitude in winter. Such channel strengthens inspring accompanied with moisture derived from the West Pacific, carrying bywestward flows along the southern pariphery of the western Pacific subtropicalhigh, turning northeastward at the Indo-China Peninsula and the South China Sea,which enhances greatly the moisture transport in the south Jiang-Huai valley. Insummer, the uppermost moisture transport roots in the Arabian Sea and the Bay ofBengal, crosses the Indo-China Peninsula and the South China Sea and enters thesouth and east part of China. Still, the cross-equatorial flows near 105°E and thewestward flows along the southern periphery of the western Pacific subtropicalhigh can contribute the effect of moisture transport in Jiang-Huai valley. Theweakest water vapor transport presents at fall, and its main source is from the Bayof Bengal and the West Pacific.(2) The difference between the average water vapor transport in Jiang-HuaiMeiyu in both drought years and flood years reaches the maximum in north China, the West Pacific and the South China Sea. The abnormally strong moisturetransport from the West Pacific and north China is might be the key factorcontributing to the anomalous precipitation in Jiang-Huai Meiyu.(3) The perturbation water vapor transport differs greatly from the averageone. The average moisture transport from the Bay of Bengal effect greatly onprecipitation in east China, while the perturbation water vapor transport affectedthe Changjiang-Huaihe River Basin is mainly from the South China Sea. The valueof perturbation moisture transport near the equator is low, while the maximumvalue presents to northern periphery of the West Pacific subtropical high over thenorthwest Pacific.(4) The perturbation of water vapor transport contrary direction compared toaverage one in Jiang-Huai Meiyu anomaly. The divergence field of difference ofperturbation water transport shows adverse phase distributions comparing with theaverage one. Contrary situation shows in moisture balance between perturbationand average transport in Jiang-Huai Meiyu. It can be concluded that theperturbation moisture transport weaken the average moisture transport, thuscounteracts the effect of anomalous Meiyu precipitation in Jiang-Huai basin causedby anomalous average water vapor transport.