Temporal And Spatial Characteristics Analysis And Evaluation Of Urban Heat Wave Risk Based On FSDAF

In recent years,the frequent occurrence of persistent high-temperature heat waves in summer has seriously affected human production and life.It is of great significance to deeply explore the risk mechanism of high-temperature heat waves,evaluate the risk of hightemperature heat waves in Zhengzhou City,and reveal the spatial distribution characteristics of high-temperature heat waves in Zhengzhou City.It is of great significance to prevent urban high-temperature disasters and provide scientific reference for high-temperature heat waves.In order to explore the risk mechanism of high temperature and heat wave at fine spatial scale,based on multi-source data such as remote sensing images(Landsat 8),nighttime light remote sensing(DMSP / OLS),population density,social statistics and meteorological station data,this paper analyzes the time characteristics of high temperature and heat wave risk in Zhengzhou City from three indexes : FHW(refers to the average number of heat waves at a place in a given year),NHD(refers to the average number of heat waves at a place in a given year),IHW(refers to the annual average value of the daily maximum temperature accumulation value exceeding the heat wave threshold of 35 ° C during the heat wave),and uses M-K trend test.The time trend of inter-decadal high temperature heat wave is analyzed,and the ARIMA algorithm is used to predict the future development trend of high temperature heat wave risk in Zhengzhou from FHW,NHD and IHW.The FSDAF space-time fusion algorithm is used to predict the surface temperature of Zhengzhou on July 26,2013,July25,2016 and July 23,2019,and obtain high time and high spatial resolution surface temperature images.Finally,the analytic hierarchy process(AHP)is used to construct a high temperature heat wave risk assessment system based on ’ high temperature risk-vulnerability-exposureadaptability ’ on the 30 m spatial resolution scale,and the spatial characteristics of high temperature heat wave risk in Zhengzhou are analyzed.The specific research contents and conclusions are as follows :(1)Analysis of time characteristics and interdecadal variation trend of heat wave risk in Zhengzhou.From the three indexes of FHW,NHD and IHW,the time characteristics of high temperature heat wave risk in Zhengzhou City are analyzed.The conclusions are as follows :The overall trend of FHW,NHD and IHW in Zhengzhou City from 1980 to 2019 is a slow upward trend,and the growth rate is greater than 0.45.The high temperature disaster in Zhengzhou City is increasing year by year,and there is a tendency to intensify.The M-K trend test was used to test the interdecadal trend of high temperature heat wave risk in Zhengzhou City.The conclusions are as follows : The M-K test curve trend of FHW,NHD and IHW in Zhengzhou City has a strong consistency on the whole,which is divided into two stages.The first stage(1980-1996)is a slow decline stage;in the second stage(1996-2019),the three values showed an increasing trend.(2)Prediction of heat wave risk trend in Zhengzhou.The ARIMA algorithm is used to predict the risk of high temperature heat wave in Zhengzhou in the next five years.The conclusions are as follows : from 2020 to 2024,the average heat wave in Zhengzhou gradually increases,the average cumulative days of average heat wave gradually accumulate,and the annual average of the daily maximum temperature accumulation value exceeding the heat wave threshold of 35 ° C is increasing year by year.This is consistent with the prediction of the IPCC’s sixth assessment report that the climate change in all regions will intensify and the heat wave will increase in the near future.(3)FSDAF spatio-temporal fusion algorithm predicts land surface temperature.Using the FSDAF space-time fusion algorithm,the 30-meter high spatial resolution surface temperature image of Zhengzhou City on July 26,2013,July 25,2016 and July 23,2019 was predicted.There were 1150 prediction windows.The results showed that the highest surface temperature of Zhengzhou on July 26,2013 was 47 °C,and the lowest temperature was 11 °C.From the perspective of Zhengzhou City as a whole,Zhongmu County,Xinzheng City,Xinmi City and Dengfeng City in the south and southeast of Zhengzhou City are the main high temperature areas of surface temperature.On July 25,2016,the highest surface temperature in Zhengzhou was 42.3 °C,and the lowest temperature was 4.5 °C.From the perspective of Zhengzhou City as a whole,Zhongmu County,Guancheng Hui District,Xinzheng City and Jinshui District in Zhengzhou City are the main high temperature areas of surface temperature.On July 23,2019,the highest surface temperature in Zhengzhou was 55.2 ° C and the lowest temperature was 5.5 ° C;from the overall point of view of Zhengzhou City,Jinshui District,Guancheng Hui District,northern Xinzheng City,Xinmi City and Dengfeng City are the main high temperature areas of surface temperature.(4)Analysis and evaluation of spatial characteristics of high temperature heat wave risk.By using the analytic hierarchy process,the spatial distribution characteristics and risk assessment of high temperature heat wave risk in Zhengzhou City from 2013 to 2019 are analyzed.The conclusions are as follows : On the whole,the high temperature risk areas in Zhengzhou City are Zhongmu County,Xinmi City and Dengfeng City in the west and south of Zhengzhou City.With the change of time,the area of these high temperature risk areas shows a decreasing trend.From the perspective of city and county scale,the extremely high risk areas of Zhongmu County and Xinzheng City gradually shrink to the west;the extremely high temperature risk area in Gongyi City gradually shifted from the southwest to the northwest of the city over time.By 2019,the extremely high temperature risk area was mainly distributed in the northwest of Gongyi City;the extremely high temperature risk area of Xingyang City gradually shifted from the southern part of the city to the northern part of the city over time;however,the extremely high temperature risk area in Zhengzhou city has little change.The innovation points of this paper are as follows: the FSDAF algorithm is used to predict the land surface temperature image with high time and high spatial resolution,which improves the accuracy of the spatial characteristics and evaluation of the risk of high temperature and heat wave.The spatial distribution characteristics of the risk of high temperature and heat wave in Zhengzhou are explored on a fine scale,and the evaluation is carried out to provide scientific reference for the prevention of urban high temperature disaster and the risk of high temperature and heat wave.