| Global warming and the frequent occurrence of extreme temperature events(ETEs)have become serious problems affecting industrial and agricultural production,human health,and social and economic development.Based on the daily temperature data of 29 state-controlled meteorological stations in Hunan Province from 1971 to 2017,this article analyzes the climate change background of Hunan Province from 1971 to2017 and the temporal change trend and space of heat waves and cold wave events in the context of climate warming.Distribution characteristics.On this basis,based on disaster risk theory and weighted comprehensive evaluation method,with 122 counties and municipalities in Hunan Province as the unit,from four aspects: hazard risk,carrier exposure,hazard environment vulnerability,and disaster prevention and mitigation capabilities,A total of 13 indicators were selected to construct a disaster risk assessment model for extreme temperature events in Hunan Province to conduct a comprehensive assessment of the disaster risk of extreme temperature events in Hunan Province.It hopes to provide a theoretical basis for understanding the trend of extreme temperature events under the background of climate warming and Hunan Province formulating scientific disaster prevention and mitigation policies for extreme temperature events.The main research conclusions of this paper are as follows:(1)From 1971 to 2017,in the context of global warming,Hunan Province experienced significant climate warming.The annual average temperature,the highest temperature in summer and the lowest temperature in winter showed an upward trend at 0.25?/10 a,0.07?/10 a and 0.31?/10 a,respectively.Catastrophe analysis showed that after 1997,the climate of Hunan Province had abruptly changed.After the abrupt change,the average annual temperature,summer maximum temperature and winter minimum temperature increased by 0.72 ?,0.22 ? and 0.88 ?respectively.(2)From 1971 to 2017,Hunan Province experienced a total of 248 heat wave events and 114 cold wave events.The number of heat wave days and cold wave days were 22,452 days and 1,793 days,respectively.The frequency of heat waves and the number of days of heat waves show an upward trend,while the frequency of cold waves and the number of days of cold waves show a downward trend.The trends over time are 0.14times/10 a,42.76 d/10 a and-0.15 times/10 a,-1.1d/10 a,but the trend is changing None of them passed the significance test with a reliability of0.05.Correlation analysis shows that there is a significant correlation between the number of heat wave days and the average temperature.In the context of a significant increase in average temperature,the number of heat wave days in Hunan Province has shown a significant increase after 1986.(3)Affected by atmospheric circulation and topography,there are obvious spatial differences in the degree of influence of heat wave events and cold wave events.In the past 47 years,the area near Youxian Station has experienced the most frequency and number of heat waves.The average annual frequency and number of heat waves are 4.66 times/a and31.21 d/a.The area near Nanyue Station is the area that has experienced the least heat waves,with no heat waves in the past 47 years.Have experienced a heat wave.At the same time,near Nanyue Station is the area experiencing the most cold wave frequency and number of days.The annual average cold wave frequency and number of days are 2.23 times/a and 3.96d/a respectively;the area near Baojing Station is the area experiencing the least cold wave frequency and number of days.The days were 0.55 times/a and 0.72d/a.In general,the frequency and number of heat waves show a spatial pattern that gradually spreads and weakens to western and northern Hunan with the high-value center in eastern Hunan and southern Hunan.The frequency and number of cold waves show a spatial pattern that gradually increases from northwest to southeast.(4)In the context of climate warming,the changing trends of heat waves and cold waves have obvious spatial differences on the provincial scale.Among the 29 meteorological stations,the frequency and number of heat waves at 26 stations showed an increasing trend,and the increase at 8stations exceeded the 0.05 significance level.Among them,the stations near the provincial capital Changsha have the fastest increase in heat wave days and the most trend.Significant;cold wave frequency and number of days show a decreasing trend in most areas including northern Hunan,western Hunan,and central Hunan,and an increasing trend in southern Hunan.However,the frequency and number of days of cold waves at all stations are not significant,so in the warming climate In the context,the possibility of cold wave disasters still cannot be ignored.(5)A comprehensive assessment of the disaster risk of extreme temperature events in Hunan Province based on the disaster risk model shows that there are 18,26,34,26 and 18 counties with low,second-low,medium,second-high,and high-level heat wave disaster risks in Hunan Province.The high-risk areas of heat wave disasters are mainly distributed in the county areas of Loudi,Shaoyang,Hengyang,Changsha and Zhuzhou;the low-risk areas of heat wave disasters are mainly distributed in Zhangjiajie City,Xiangxi Prefecture,Huaihua City,Yueyang City and Chenzhou City.Among them,Liuyang City of Changsha City has the highest heat wave disaster risk level,and Nanyue District of Hengyang City has the lowest heat wave disaster risk level.There are 21,33,23,26,and 19 counties and cities with low,second-low,medium,second-high,and high-level cold wave disaster risks.The high-risk cold wave disaster areas are mainly located in Shaoyang City,Loudi City,In the county areas of Xiangtan City,Hengyang City,Changsha City and Yueyang City,the cold wave disaster low-risk areas are mainly concentrated in Zhangjiajie City,Xiangxi Prefecture and Huaihua City in western Hunan.Among them,Liuyang City of Changsha City has the highest risk level of cold wave disasters,and Wulingyuan District of Zhangjiajie City has the lowest risk level of cold wave disasters. |
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