| Atmospheric process of hydrological cycle is one of the important processes of hydrological cycle,which greatly affects the structural composition and evolution of the global ecological environment system and water resources system,and to some extent changes the way of production and life of human beings.Atmospheric water vapor is also the key to regional hydrological cycle and the source of regional precipitation.The water diversion project in Central Yunnan is a century project to solve the uneven spatial distribution of water resources in yunnan province,and a strategic project,a support project,a livelihood project and an ecological project for yunnan's economic and social leaping development.Therefore,the study of water vapor transport and its budget in the Jinsha River Basin upstream of the intake point of the water diversion project in Central Yunnan can better formulate management measures and strengthen the management of water resources in the basin,and provide a basis for the comprehensive management and development of the basin.This paper is based on the topographic data ASTER GDEM V2,the ECMWF ERA-Interim monthly reanalysis data(0.25°×0.25°)from 1979 to 2018,and the monthly precipitation data of 22 meteorological stations in different provinces from 1979 to 2018 provided by China Meteorological Data Network.This paper systematically and comprehensively study the spatiotemporal variation characteristics of water vapor content and precipitation,water vapor transport characteristics,water vapor budget and its variation characteristics in the Jinsha River Basin upstream of the intake point of The water diversion project in Central Yunnan during the 40 years from 1979 to2018.The main contents and conclusions are as follows:(1)The water vapor content over Jinsha River basin upstream of the water intake point of the water diversion project in Central Yunnan decreases from south to north and from east to west.The water vapor content in each period presents an inverted"U"shape in the southwest and a positive"U"shape in the southeast.The mean annual water vapor content show an increasing trend with a linear change rate of 0.2mm/10a.The distribution pattern of the mean annual precipitation increase gradually from northwest to southeast in the basin,which is consistent with the change characteristics of"summer,autumn,spring and winter".The mean annual precipitation has a slight upward trend over the years.The precipitation in the headwaters and lower reaches of the river basin show a significant increasing trend,while there is no significant change trend in the middle reaches.The water vapor content and precipitation in the basin in four seasons from large to small are in order of summer,autumn,spring and winter.The distribution of the average monthly water vapor content and precipitation over the years presents a single peak pattern,with the highest value appearing in July and gradually decreasing to both sides,roughly forming a symmetrical distribution.There is a weak correlation between annual mean water vapor content and annual mean precipitation in the basin,and the correlation coefficient is 0.28.The seasonal correlation shows significant differences,with a moderate correlation in summer,and the highest correlation in July with a correlation coefficient as high as 0.809.In spring and autumn,the correlation is low,and in winter,the correlation is extremely weak.The monthly correlation analysis can provide important guidance for the precipitation in the basin.(2)The water vapor from westerly over the northern Arabian Sea and the water vapor from the Bay of Bengal are the main factors influencing the Jinsha River basin upstream of the water intake point of the water diversion project in Central Yunnan,and the westerly water vapor transport is dominant.The spring is influenced by the southwest westerly water vapor conveyor belt originating from the northern Arabian Sea.In summer,water vapor mainly comes from the Bay of Bengal and the Arabian Sea.The main water vapor sources in autumn include westerly water vapor transport,strong easterly water vapor transport over the western Pacific and water vapor transport over the Bay of Bengal.Water vapor in winter is mainly supplied by westerly winds in the north branch of the Qinghai-Tibet Plateau.Water vapor transport in the basin is mainly in the zonal direction from west to east,and the intensity is about 30-130 kg·m-1·s-1.The divergence and convergence areas are distributed in a ring pattern with different sizes and densities,concentrated areas of them are mostly at the north and south ends.Compared with the lower atmosphere,the intensity of divergence and convergence in the upper atmosphere is somewhat reduced.Seasons change alternately,with summer as water vapor convergence zone and winter as water vapor divergence zone.(3)The average annual net water vapor budget in the Jinsha River basin upstream of the intake point of the water diversion project in Central Yunnan is 38.13 km3,and the annual variation increases at a rate of 3.25km3/10a.The output boundary of atmospheric water vapor is only the eastern boundary,and the rest boundary is the input boundary of water vapor throughout the year,among which the western boundary contributes the most,averaging about76%.The net budget of water vapor present a state of"surplus"and the amount of"surplus"increased gradually.From the change characteristics of water vapor budget in different seasons,the surplus of water vapor in spring,summer,autumn and winter is all presented.The contribution of summer to the annual net water vapor budget is the largest,which is about58.4%,and the contribution of spring and autumn is similar,which is about 9%.Except winter,the water vapor transport in all seasons showed an upward trend.In the monthly water vapor budget,the net water vapor input from February to October was more than 200 km3.The rainy season(April to October)was the net input period,in which the maximum was from June to September,and the dry season(November to March of the following year)was the net output period. |
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