Study On The Prediction And Spatio-temporal Changes Of Extreme Precipitation In Hunan Province

Extreme precipitation is one of the most destructive natural disasters in the world.Under the background of global warming,extreme precipitation events become more and more intense,and their impact on human society is further expanded.Therefore,it is of great theoretical and practical significance to study the spatio-temporal evolution characteristics and possible influencing factors of extreme precipitation.In this paper,the spatial and temporal characteristics of extreme precipitation events in Hunan Province are analyzed from 1960 to 2015 by using the measured daily precipitation data of 88 stations in Hunan Province.Combined with the daily precipitation data,the simulation performances of different CMIP5 global climate models on extreme precipitation indexes are evaluated.On this basis,the averaged results of the select models are used to project the relative change of extreme precipitation over Hunan in the 21 st century(2020~2100).Finally,the teleconnection between extreme precipitation and atmospheric circulation index in Hunan Province is further studied by stepwise variable selection and multiple linear regression methods.The main conclusions are follows:(1)In the past 57 years,the PRCPTOT,SDII,Rx1 Day,Rx5Day,R95 p and P95 p have increased in Hunan Province.The areas with significant upward trend areNorth of xuefeng mountain(SDII,Rx1 Day,Rx5Day,R95 p,P95p),south of southeast hunan(SDII,R95 p,P95p),and north of dongting lake plain(SDII),while heng shao basin is the main areas where all indexes show a downward trend.(2)Extreme precipitation mainly occurs from late April to early September.Since 1990 in hunan province,the ending time of extremeprecipitation events(R95p)in the whole province has shown an obvious trend of postponing,indicating the risk of increasing extreme precipitation in autumn.In addition,the starting time of extreme precipitation in southeast hunan also shows an obvious early trend,that is,the duration of extreme precipitation in this region has been extended,and the risk of extreme precipitation in the future will be greater.(3)The global climate models can well fit the spatial distribution characteristics of the extreme precipitation index in hunan province.Compared with the base period(1961-2005),PRCPTOT and SDII in hunan province will continue to rise in different periods in the future,and the increase will be stronger under RCP4.5.Under RCP8.5,the increase of PRCPTOT in northwest and southeast hunan is the greatest.Under RCP8.5,SDII in hunan shows a certain downward trend.(4)Under the different climate backgrounds,Rx1 Day and Rx5 Day in northeast Hunan and southeast Hunan(except east and southeast Hunan)show an upward trend in different periods in the future.It shows a downward trend,and gradually transformed into an increasing trend in the middle and late stages.These two changes are more significant in the context of RCP8.5.(5)Under the background of RCP4.5,R95 p in Hunan Province in different periods in the future shows basicallyan increasing trend.Under the background of RCP8.5,R95 p in central Hunan,central western Hunan and southeastern Hunan shows a downward trend in the first half of the 21 st century,In the late 21 st century,it turns into an upward trend.The change pattern of P95 p is basically the same as that of R95 p.(6)The summer extreme precipitation in Hunan Province has six characteristic subregions,and the summer extreme precipitation in each subregion is affected by multiple climate factors with different time lags.The results show that the main impact factors are AO-10 and AMO-9 in R1,AO-10,PNA-3 and SOI-11 in R2,WPWP-1 in R3,AO-4 and WP-6in R4,AO-2 and PNA-9 in R5,and TNI-4 in R6.At the same time,wavelet crossover analysis shows that there is a significant consistent correlation between summer extreme precipitation and its influencing factors at different time scales in various regions.