Relationship Between Extreme Precipitation And Water Cycle In The Jianghuai Region

In recent years,the frequency of extreme weather events has increased and the intensity has continued to increase.Under the background of global warming,air's ability to store water vapor will increase accordingly,and the increase of water vapor will cause the water cycle to change.Water cycle variation has an important impact on extreme precipitation in the Jianghuai Region,but relatively few studies have focused on the relationship between water cycle and extreme precipitation.Exploring the relationship between the two is helpful to enhance the understanding of the extreme precipitation in the Jianghuai Region and its relationship with the water cycle,as well as an in-depth understanding of how the water cycle affects the formation mechanism of extreme precipitation,and provide a scientific basis for the prediction and early warning of extreme precipitation and flood disasters in the Region.This article uses daily precipitation data of 220 meteorological stations in Jianghuai Region(28°N?34°N,east of 110°E)from 1961 to 2015,as well as NCEP/NCAR reanalysis data of geopotential height,wind,OLR and specific humidity field data over the same period.The paper first analyzes the characteristics of the temporal and spatial variation of summer extreme precipitation index in the Jianghuai Region and selects typical years of extreme precipitation.Based on this,the paper further explores the background field configuration,water cycle characteristics of typical years of extreme precipitation,and the characteristics of water cycles of typical events of extreme precipitation based on Euler method and Lagrange method.The results are as follows:(1)The extreme precipitation index is large in the southern part of the Jianghuai Region,small in the north,rising in the east,and falling in the central and western parts.The first eigenvector is basically positive,and the second eigenvector appears as an out-of-phase distribution.Strong(weak)extreme precipitation years The West Pacific subtropical high is strong(weak),and the East Asia/Pacific(EAP/PJ)teleconnection type shows positive(negative)phase distribution.The Jianghuai Region is located at the northwest(southwest)corner of the anticyclone,and the OLR anomaly is negative(positive).Water vapor Flux increases,converges(weakens,diverges).(2)In strong(weak)extreme precipitation years,the water vapor content in the Jianghuai Region is between 3000?5000mm,the water vapor utilization efficiency is high(low)below 0.1,and the precipitation recirculation rate is between 0.1?0.3;using transient water vapor flux studies,it is found that in the Jianghuai Region in summer It is a source of transient water vapor.In autumn and winter,the transient water vapor budget has the same magnitude as the average water vapor budget;the water vapor in typical years of extreme precipitation mainly comes from the Indian Ocean,the Bay of Bengal-South China Sea,the Western Pacific,Eurasia,and local areas.Among them,thewater vapor contribution rate of the Indian Ocean and the Western Pacific is greater;Compared with the strong extreme precipitation year,the weak extreme precipitation year in the Bay of Bengal-South China Sea and Eurasian water vapor contribution rate has declined.(3)On the maximum precipitation day of a typical event of extreme precipitation,the water vapor content in the Jianghuai Region is between 20?70mm,there may be no precipitation in the small precipitation area,the precipitation in the large precipitation area exceeds 50 mm,and the maximum can reach 200 mm,and the precipitation recirculation rate is between0.06?0.5;During the typical event of extreme precipitation,the early water vapor mainly comes from the Indian Ocean-South China Sea area,and the later water vapor mainly comes from the Western Pacific.The changes in the water vapor budget at the southern boundary and the total water vapor budget are most similar,but the water vapor budget at the northern boundary cannot be ignored;The three extreme precipitation events have common points and different points.Through the analysis of the differences,this paper finds that the strength of the anti-cyclone in the western Pacific will affect the location of the confluence of water vapor in the Indian Ocean-South China Sea and the water vapor in the Western Pacific,which in turn will affect the water vapor transport path and contribution rate in each sea area.In addition,the initial specific humidity of the air block has a good linear relationship with the initial height.