Study On Extreme Events Of Temperature And Precipitation Over Guangxi Zhuang Autonomous Region 1960-2015

Global warming has become an indisputable fact.Under the background of globao warming,the extreme weather and climate events occur very frequently.Therefore,the public life and health and socio-economic development have been greatly affected.In this paper,the daily temperature series of 21 stations and precipitation series of 20 stations in Guangxi from 1960 to 2015 were established based on the dataset of CHTM3.0 with homogenized daily Tmax/Tm/Tmin records during 1960–2013,developed by the Institute of Atmospheric Physics,Chinese Academy of Sciences.The daily temperature,precipitation records during January 1,1960-February 29,2016 were provided by the National Meteorological Information Center(NMIC)of the China Meteorological Administration(CMA).According to the local climate characteristics of Guangxi,15 extreme temperature indices and 16 extreme precipitation indices were selected from the 27 core extreme climatic indices defined by the Expert Team on Climate Change Detection and Indices(ETCCDI).The temporal variation characteristics of the extreme climatic indices in Guangxi near 56 a were calculated and tested by linear trend estimation method.The increase or decrease and trend transition characteristics of each extreme climate index were studied using the wavelet theory and the piecewise linear fitting model.This study can explore the changing pattern of extreme weather events in Guangxi and provides scientific basis for improving the prediction level of Guangxi extreme weather events and the ability of disaster prevention and mitigation.The main results are as follows:(1)The average intensity,frequency and continuous indices of the extreme cold events in Guangxi were generally decreased and the extreme warm events were enhanced and increased in all respects.The indices associated with the daily minimum temperature were generally increases stronger and more obviously than the indices of the daily maximum temperature.The extreme temperature indices with significantchange trends like,minimum value of daily minimum temperature(TNn)in summer,autumn and winter,minimum value of daily maximum temperature(TXn)in autumn,maximum value of daily minimum temperature(TNx)in four seasons,maximum value of daily maximum temperature(TXx)in spring,extreme temperature range(ETR),number of frost days(FD),number of tropical nights(TR)showed consistently change trends in Guangxi,but the changing magnitudes showed large region difference.The spatial distribution of the change trend of the other indices were manifested by the increase or decrease,the rise or fall,and the regional differences of the individual indices were also very obvious.(2)The average precipitation indices in Guangxi showed increasing trends besides maximum consecutive 5-day precipitation(Rx5day)in spring,the precipitation amount in post-flood season(PFS-PRCPTOT)and the maximum length of wet spell(CWD),and the trends occurred in autumn and winter(or non-flood season)were faster and more significant.The change of annual total precipitation in wet days(PRCPTOT)was mainly affected by the precipitation amount in pre-flood season and post-flood season before 2000,and the effect of precipitation amount in non-flood season(NFS-PRCPTOT)was more significant since 2000.The spatial distribution of Rx5 day in winter,simple precipitation intensity index(SDII)and SDII in non-flood season(NFS-SDII)showed consistently increasing trends,and the other extreme precipitation indices showed different regional differences.(3)The first principal period of TNn,TXx were above 10 a,larger than the TXn and TNx(4-6a),in the rest extreme temperature indices,which associated with the cold events their first principal period(14-28a)were larger than the indices associated with the warm events(9-14a).The extreme precipitation indices reflects the frequency of heavy precipitation(R95p,R25 mm,R50mm),and PRCPTOT,SDII,CDD(the maximum length of dry spell),the 6 indices their first principal period were 21-29 a,the first principal period of CWD was 14 a,the first principal period of the pre-flood season,the post-flood season and the non-flood season were 5-8a,11 a and 26 a.(4)Each extreme climate index in recent 56 a had occurred trend variation.In the number of variations,appeared time and the interval of change were different.The results show that,in the trend of overall climate warming,the extreme cold events in Guangxi,such as TXn and FD still exist in stage enhancement,and the extreme warm events such as TXx,Warm speel duration index(WSDI),high temperature days(HTD)will also be stage weakened.The frequency of heavy rain and rainstorm and thePRCPTOT which closely associated with them showed obvious interdecadal fluctuation characteristics after the 1980 s,and showed significant increasing trend in the past 10 years.The total precipitation and precipitation intensity in the pre-flood season and post-flood season changed to decreasing trend around 2000,the change trend of non-flood season indices enhanced from the end of the 1990 s,and the change of the PRCPTOT had a significant impact,after 2007,they all showed a significant increasing trend.And the change trend of CDD was the typical variable rate mutation form,in 1989,the variable rate increased and the overall trend decreased.The CWD showed a significant reduction trend after the last trend change in 1998.