| Drought and flood disaster is one of the most common and serious natural disasters of meteorological disaster in the world,it is spreading widely and causing serious losses.Xiang-Gan-Zhe area is located in the southern region of China,it is affected by the monsoon very significantly,and have a corresponding on global warming,drought and flood disasters occurred frequently and seriously.There is an important commodity grain base and the industry and agriculture develop rapidly in this region,drought and flood disasters have many adverse effects on it and affect the development of the national economy.So,study the temporal evolution of drought and flood and judge the trends of drought and flood in this area have an important significance.Based on daily temperature,precipitation and other meteorological data of 47 meteorological stations in Hunan Jiangxi and Zhejiang of the south of the Yangtze River,using Standardized Precipitation Evapotranspiration Index,linear trend method,M-K mutation testing,IDW interpolation method,mathematical statistics,symmetry method and so on,analysis the background of climate change,the evolution characteristic of drought and flood disaster and occurrence trend of drought and flooddisaster etc.Research the impact factors on drought and flood,the conclusions are as follows:(1)It shows a warming trend in 1961-2015 in there provinces of Xiang-Gan-Zhe area,and the warming rate is 0.21 ?/10a,occurring a significant mutation in 1997.The increase of temperature in spring is the most significant,followed by winter,and the temperature change rate in summer and autumn is lower than that in the three provinces.The spatial distribution of air temperature is highest in the central and southern regions,followed by the eastern region and the lowest in the west.Each station shows a warming trend,the highest heating center is located in the eastern part of Xiang-Gan-Zhe area,the weak heating center in the southwest(Hunan province)of the Xiang-Gan-Zhe area.And the spatial distribution of the warming amplitude shows an increasing trend from the west to the east.The annual precipitation of the three provinces in the south of the Yangtze River shows a rising trend,the rising speed is 21.29mm/10a,and the abrupt change of precipitation is not obviously.Precipitation is mainly concentrated in the spring and summer,the precipitation of summer and winter shows an increasing trend,spring and autumn precipitation are decreasing.The spatial distribution of annual precipitation shows high in central regions,low in the eastern and western regions.The high value center is located in guixi and yushan of Jiangxi province,the low value center is located in quzhou,lishui of Zhejiang province and Zhijiang of Hunan province.The precipitation in the western region is decreasing in the spring and autumn,the summer precipitation shows an increasing trend in most of stations,the winter precipitation presents increasing trend too,and the.spatial distribution presents central and eastern regions are higher than western regions.(2)There is an obviously trend of humidification in research region in recent 55 years.The drought year mainly occurred in 1963,1968,1971,1978,1979,1985,1986,2003,2007,2009,2011,2013,the most serious drought occurred in 1971.The flood year mainly occurred in 1961,1970,1973,1975,1983,1989,1994,1997,1998,1999.2002,2010,2012,2015,the most serious flood occurred in 2012.Hunan shows a slight trend of drought,Zhejiang and Jiangxi show a trend of humidificatio.There is a waterlogging trend in summer,autumn and winter,the frequency of flood and drought is well-matched in spring.The spatial distribution of drought frequency shows higher in the east and the west and shows lower in the central area.The heavy drought high frequency area is located in Zhejiang province and the middle of Hunan province,the low frequency region is located in central area of three provinces.The spatial distribution of flood frequency presents high value in the vast majority of central area,low value around the edge region,high frequency region mainly in moderate flood.The heavy flood frequency region is located in the southeast of Hunan province and the eastern part of Jiangxi province.In the middle of Hunan Province named Shaoyang is a region in high incidence area with heavy drought and flood.Drought tendency rate showed an increasing trend from the west to the East.The distribution characteristics of spatial year of drought and flood disaster performance that logging center transfer from the west to the East,spatial distribution of drought is still in Hunan Province,followed by Jiangxi province;the time of drought and flood occurrence distributes alternately,there is a significant transformation of drought and flood in space.(3)Drought and flood prediction results in recent years in future are as follows:the occurrence of drought and flood in Xiang-Gan-Zhe area is more likely occur in 2017 and 2023.The summer drought,autumn flood,winter rain and snow disaster occur in Hunan province is more likely happen in 2017,2020 and 2019.The spring flood,summer flood,summer drought,autumn flood occur in Jiangxi province all are more likely happen in 2017.The summer drought,summer flood,autumn floods,winter rain and snow disaster occur in Zhejiang province is more likely happen in 2018,2017,2017(2018),2017.(4)The drought and flood disasters in Xiang-Gan-Zhe area mainly occurred in the stage of weak or weak solar activity.The drought happened in Zhejiang province appeared in solar activity or strong strengthening stage,the drought and flood happened in Jiangxi Province and Hunan province,flood happened in Zhejiang province mainly occurred in the stage of weak or weak solar activity.Drought and flood mainly occurred in the stage of weak or weak solar activity and the drought frequency is more than flood.The frequency of drought occurrence is greater than that of waterlogging in the sunspot maximum years.The relationship between drought and flood disaster and ENSO:the SPEI index of the three provinces in the four seasons is mainly negative correlation with SOI,which is most significant in spring and winter.The drought and flood disaster is easy to happened in ENSO year,heavy drought are easy to appear in the El Nino years,heavy flood are easy to appear in La Nina years.There is a certain correlation between the intensity of ENSO event with flood anddrought disasters,and there is time lag.The East Asian Summer Monsoon have great influence on summer precipitation,and also have a strong relationship with drought and flood in summer.There is less precipitation and drought happened in weak East Asian summer monsoon years,and more precipitation and flood happened in strong East Asian summer monsoon years.Topography has a certain effect on the drought and flood disasters in the study area. |
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