Dynamic analysis and influence mechanism of thermal environment space in Nanjing City block scale

The significant change of land surface temperature can lead to the urban thermal environment effect, which will cause serious urban heat wave under the influence of global climate change, and bring great challenges to the urban ecological environment, human survival and sustainable development. For this study, the primary urban roads were selected, and the middle line of the road and the river of Nanjing were used as the boundary line for block division. Land surface temperature (LST) data and seven influencing factors were used to study the multiple effects of land surface temperature in Nanjing. The influencing factors included impervious surface area (ISA), night lighting intensity (NTI), population (POP), gross domestic product (GDP), digital elevation model (DEM), normalized vegetation index (NDVI), land use and land cover (LULC). Heat island intensity (UHIER) was calculated for each block as well as the values of the influencing factors, ISA, NTI, POP, GDP and NDVI. The study involved Pearson correlation coefficient of potential influencing factors using SPSS software, constructing geographically weighted regression model (GWR) of the average annual land surface temperature and influencing factors to analyze the correlation between annual average land surface temperature and multiple influencing factors in Nanjing in 2019. The study found that the urban thermal environment of Nanjing is mainly in the city center, showing the phenomenon of outward diffusion from the center, with a relatively low total area. The spatial distribution of heat island in Nanjing was significantly affected by land use types and landforms, with the intensity of heat island higher in the construction land area and plain area in the main urban area of Nanjing. The intensity of heat island in Nanjing was greatly affected by normalized vegetation index, the intensity of light at night and the impervious surface area. The research results provided insight into the influence mechanism of the urban thermal environment, which can be used to plan and mitigate the urban thermal environment effect effectively.