Analysis Of The Influence Of Urbanization Typical Extreme Climate Events

With the global climate change,the crowded nature of extreme climate events becomes more obvious,their frequency and intensity gradually increase,and the scope of influence continues to expand,which has a great impact on people's lives and property safety.The results of relevant studies have shown that the impact of urbanization is one of the important reasons for the frequent occurrence of extreme climate events.We can improve cognition of past climate change characteristics,and enrich climate change attribution analysis and provide basis for urban to adapt and retard climate change,as well promote regional sustainable development.Through study the characteristics of spatial-temporal changes in extreme climate events,explore the impact of urbanization on extreme climatic events.Liaoning Province was selected as the study area.Based on the daily temperature and precipitation data of 22 meteorological stations from 1957-2015,the characteristics of temporal and spatial changes of extreme climatic events were divided by empirical mode decomposition(EMD)and Kriging interpolation,and the influence of urbanization on extreme climate events were analyzed by generalized extreme values.The results show:(1)The extreme high-temperature events increase at a rate of 0.5d/10 years,and the fastest changes occur at Jianping,the rate is greater than 1.1d/10 years.Benxi,Fushun and Kaiyuan are the lowest.Spatially,extreme high-temperature rate changes gradually decrease from southwest to northeast.There are significant regional differences in extreme high temperature events in the central region.In space,the total number of extreme high temperature days that take Kaiyuan,Fushun,Qingyuan as the center decrease toward both sides.(2)The extreme cold events dropped at the rate of-1d/10 years,Kuandian's rate was less than-2.4d/10 years,it is the fastest.On the other hand,Zhangwu showed an increasing trend.The space change has two low(Jianping,Kuandian)-high(Zhangwu)central areas,which gradually increase from the southeast to the west.In space,the total days of extreme low temperatures is gradually decreasing from southwest to southeast and north.(3)The rate of extreme precipitation days decreases slightly with the trend of-0.2d/10 years,and the volatility is greater.Xiuyan station has the fastest decline rate of-0.5d/10 years.The spatial contour of the rate of change divides the Liaoning area into two parts,among which the southeast of Liaoning Province changes significantly,Owing to it is closer to the sea and has abundant moisture.In space,the total days of extreme precipitation events show obvious reduction from coastal to inland.(4)The rate of extreme drought events declined at-0.6d/10 years,and the average annual drought days are 22 days.Among them,Xiuyan has the largest downward trend,which is-1d/10 years.Chaoyang,Fuxin,Suizhong,and Zhangwu changed little,their rate between-0.3--0.5d/10 years.In space,the rate take Xiuyan as the center gradually decreases to around.The total days of extreme drought events have a high(Jianping)and a low(Qingyuan)center.(5)Urbanization has a significant impact on extreme climate events.In extreme high temperature events,the contribution rate of urbanization impacts reached more than 50%.In extreme cold events,there were 4 groups which contribution rate were ? 60%.In extreme precipitation events,there were 5 groups exceeding 70%;In extreme drought events,except for the contribution rate of Shenyang-Fuxin that is 80%,other contribution rates are 100%,indicating that unknown factors may have impacts on it.The impact of urbanization on extreme high temperature events is greater than that of extreme cold events,and the impact on extreme drought events is higher than that of extreme precipitation events.