| With the rapid development of the economy,the acceleration of the urbanization process,and large-scale population aggregation,human activities have significantly impacted the urban regional climate.The heat island effect has caused severe harm to the livability and environmental quality of cities.It has become one of the key and hot issues in the current urban thermal environment research.At the same time,the sensitive temperature change of urban surface temperature in the warming process makes the challenge of urban high temperature more difficult.Severe temperature changes will seriously threaten human health,leading to increased mortality and incidence rate.Therefore,this paper takes urban high temperature and sensitive temperature changes as the research object,discusses the influencing factors of urban high temperature and sensitive temperature changes,the distribution characteristics and spatial aggregation patterns of heat exposure risks,and the social inequality of heat exposure risks,to provide a reference for urban spatial planning and comprehensive treatment of the thermal environment.Using Shanghai as the study area,the paper first calculated the heat island intensity values reflecting urban high temperature and the warming sensitivity index values reflecting urban sensitive temperature changes.We also analyzed the magnitude of the explanatory power of normalized difference vegetation index(NDVI),modified normalized difference water index(MNDWI),normalized difference built-up index(NDBI),road network density,and nighttime light index on urban high temperature and sensitive temperature variation and the interaction between each detection factor by using the geographic detector model,and spatially superimposed the local climate zone(LCZ)classification results with heat island intensity values and warming sensitivity index values to explore the divergence patterns of urban high temperature and sensitive temperature variation under different types of local climate zones.Subsequently,heat exposure risk assessment indices based on heat island intensity-population density and warming sensitivity index-population density were constructed to assess the heat exposure risk status of urban high temperature and sensitive temperature change,and global and local spatial aggregation patterns of heat exposure risk were analyzed.Finally,based on the urban high temperature and sensitive temperature change heat exposure risk values and census data,an ordinary least squares model(OLS)and a geographically weighted regression model(GWR)were used to analyze the heat exposure inequality status of 10 types of social groups at citywide and street scales,and the severity of street-scale social inequality was determined by comparing significant regression coefficients.The main research components of the paper and the results of the study are the following three aspects:(1)Study on the distribution characteristics and influencing factors of urban high temperature and sensitive temperature changesThe heat island intensity and sensitivity indices in Shanghai show a distribution of high center and low surroundings.The sub-districts with high urban heat island intensity and sensitivity index were mainly Waigaoqiao Free Trade Zone,Zhijiang West Road Sub-district,Baoshanlu Sub-district,and Yuyuan Sub-district.The magnitude of the explanatory power of the urban hign temperature impact factor is NDBI>nighttime lighting index>NDVI>road network density>MNDWI,and the interaction between NDBI and other factors were stronger;the magnitude of the explanatory power of the sensitive temperature change impact factor is nighttime lighting index>NDBI>road network density,and the interaction between nighttime lighting index and other factors were stronger.Meanwhile,it was found that overall the heat island intensity and warming sensitivity index within the building types were higher than the land cover types.Compact high-rise buildings(LCZ1),heavy industrial buildings(LCZ10),and compact mid-rise(LCZ2)were the building types with the highest heat island intensity and most sensitive to temperature change LCZ,and dense trees(LCZA)and water bodies(LCZG)and low vegetation(LCZD)were the land cover types with the lowest heat island intensity and least significant temperature change LCZ.(2)Study on risk assessment of thermal exposure to urban high temperature and sensitive temperature changesIn Shanghai,the heat exposure risk of urban high temperature and sensitive temperature change is generally high in the city center and low in the suburbs,and the sub-districts with higher heat exposure risk of urban high temperature and sensitive temperature change were mainly North Sichuan Road Sub-district,Gonghexinlu Subdistrict,Yuyuan Sub-district,and Ganquan Road Sub-district.From the spatial aggregation results,there is a positive spatial autocorrelation of the heat exposure risk of urban high temperature and sensitive temperature change,and there is a certain aggregation phenomenon in the spatial distribution of heat exposure.The hot spot areas of heat exposure risk were all clustered in the central city of Shanghai,while the cold spot areas were concentrated in Chongming,Qingpu,Songjiang,Jinshan,Fengxian,and most areas of Pudong New Area.Compared with the urban hign temperature exposure risk assessment results,the sensitive temperature change heat exposure risk is more concentrated and distributed in the central urban area,and it does not show an obvious outward extension and gradient decreasing feature.In terms of the number of hot and cold spot sub-districts,the number of streets in hot and sub-cold spot areas for sensitive temperature change heat exposure risk is more than the results for urban high temperature,while the opposite is true for the number of sub-districts in sub-hot and cold spot areas.(3)Study on social inequality of heat exposure risk in urban high temperature and sensitive temperature changesThe results of social inequality exposed on a citywide scale show that agricultural populations were underexposed to urban high temperatures and sensitive temperature changes on a citywide scale,while ethnic minorities were only underexposed to sensitive temperature changes.The social inequality results of exposure at the subdistrict scale show that women,elderly housing population,population with low educational background,children,and the elderly all have different degrees of overexposure to urban high temperature and sensitive temperature changes at the subdistrict scale,while people without real estate only have negative exposure results.The results of social inequality on the sub-districts scale show that the proportion of people who were excessively exposed to the risk of urban high temperature and heat exposure in the street is in the order of elderly housing population>women> population with low education background>elderly people>children>people without real estate;The proportion of people who were excessively exposed to the risk of heat exposure due to sensitive temperature changes in the sub-districts is in the order of elderly housing population>women>elderly people> population with low education background>children>people without real estate.In addition to people with low education background,people who were excessively exposed to sensitive temperature changes were more widely distributed.The number of sub-districts with the most unequal and sub unequal comprehensive heat exposure risks,and the results of urban high temperature heat exposure risk,among the elderly housing population>women>the elderly>children;Among the results of heat exposure risk for sensitive temperature changes,the elderly housing population>women>the elderly>children.The elderly housing population and women were the most exposed social groups to urban high temperature and sensitive temperature changes in cities. |
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