Single-factor and bivariate association mechanisms of the land surface thermal environment in the central urban area of Nanjing

Abstract

Urban land surface thermal conditions have become an important issue in studies of ecological security, residents’ health, and sustainable urban development. Taking the central urban area of Nanjing as the study area, this study uses remote-sensing and geospatial data from 2015, 2020, and 2025 to examine changes in land surface temperature. LST was used as the dependent variable, while natural, social, and economic factors were incorporated into the explanatory-factor framework. On this basis, GIS spatial analysis, XGBoost, and the geographical detector model were combined to identify the spatiotemporal characteristics of LST and further explain the factors shaping its spatial differentiation.The results show that: (1) From 2015 to 2025, LST in Nanjing varied clearly across space. Higher temperatures appeared mainly in the urban core, dense built-up areas, and along traffic corridors, whereas lower temperatures were found around water bodies, green spaces, and areas with more varied terrain. (2) The XGBoost feature-importance results indicate that the dominant factors affecting LST changed by stage. NDBI was the leading factor in 2015, GHSL became dominant in 2020, and the importance of VIIRS increased in 2025. This change suggests that the mechanism shaping Nanjing’s land surface thermal environment gradually shifted from built-up expansion and the growth of hard underlying surfaces to the combined effects of built-up spatial stock, human-activity intensity, and urban functional vitality. (3) The geographical detector results further show that interactions between factors improved the explanatory power for the spatial differentiation of LST. DEM appeared repeatedly in combinations with high explanatory power, indicating a terrain–construction coupling characteristic in Nanjing’s LST pattern. Overall, Nanjing’s land surface thermal environment is jointly shaped by the built environment, human activities, vegetation and water bodies, and topographic conditions. Future thermal-environment governance in Nanjing should coordinate terrain, construction intensity, population activity, and blue-green space; control the proportion of impervious surfaces in high-intensity construction areas; and improve blue-green space and ventilation-corridor networks. These measures can provide support for urban renewal, heat-risk prevention, and resilient-city development.