| Under the background of global warming,the urban heat island effect(UHI)threatens the lives and health of residents.In summer,stable heat islands are more severely affected than expansion and transfer heat islands,residents who living in the center of stable heat islands have extremely high heat-related health risks.Define the multiple frequency urban heat islands(MFUHI)as:the heat island which stable for many years in summer and have a large area and a well-connected high-temperature center.This study takes the area within the Beijing Sixth-ring Road as an example,and uses the Landsat data of the third phase,combined with morphological spatial pattern analysis and superposition analysis,to identify the spatial distribution of MFUHI in Beijing from 2011 to 2017.Based on field surveys and remote sensing data in key areas,the MFUHI are classified.The relationship between land surface temperature and landscape indicators were explored by ordinary least-squares(OLS)regressions,and the reasons for the formation of MFUHIs were analyzed by using the magnitude difference of landscape components in city and key zones.Based on the "exposure-sensitivity-adaptation" framework,a questionnaire interview was conducted with 1789 residents(5 ‰ sampling)who lived and worked in the key zones to evaluate the heat vulnerability of the residents and explore the spatial distribution differences and causes.The study reached the following conclusions:(1)there are four large-scale long-term heat islands in the sixth ring road of Beijing,including four types of heat centers of traffic,historical blocks,commercial districts and villages in the city,which are respectively located in the xicheng district of the city center,and fengtai district and chaoyang district on the edge of the city.Measured temperature data validation of heat island area temperature is much higher than other regions for a long time,long-term heat island area and the highest temperature of UHI area green space and the difference between the average temperature is 10.3 ? and 4.7 ? respectively,and long-term heat island area of UHI area proper the difference between the highest temperature and the average temperature of 8.5 ? and 3.3 ?,respectively,the UHI area built up area between green space and the highest temperature and the difference between the average temperature of 1.8 ? and 1.4 ? respectively.(2)The results of OLS demonstrate that NDVI and proportion of water area had a good mitigation effect on UHI.ISA and building density had a warming effect on UHI.For building-floor,the relation showed a piecewise linear with LST.The relationship between building-floors and LST was piecewise linearly correlated.Below the fifth floor,the building-floors showed a positive correlation with LST and above the fifth floor,the building-floors is negatively correlated with LST.Statistical analysis shows that the MFUHI has higher impervious surface coverage than other parts of Beijing,the blue-green space and facilities are extremely lacking,and the buildings exhibit high-density and low-floor characteristics,these are the reasons leading to the stability.(3)The statistical results of the questionnaire show that the vulnerable groups are mainly migrant workers,low income,low education,older residents and women.In the future,high temperature risk prevention should pay more attention to the special population in these specific areas.Resident thermal vulnerability evaluation results show that the long-term heat island type of vulnerability is ranked as Integrative wholesale market > City villages > Hutong residential district > Green residential district.There are spatial differences in the impact of social public service facilities on residents.The regional vulnerability near the city center is less than that in suburban areas,and the regional vulnerability of mixed commercial and residential functions is greater than that in residential areas. |
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