Understanding the relationship between 2D/3D variables and land surface temperature in plain and mountainous cities: Relative importance and interaction effects

The escalating prevalence of extreme heat events has intensified scholarly interest in understanding the nexus between urban built environments and extreme heat. This study focuses on the central urban areas of Chengdu and Chongqing, sizable Chinese cities that share a common building climate zone but are divergent in topography and landform (i.e., plain versus mountainous). Leveraging spatial regression, XGBoost, and Shapley additive explanation techniques, we scrutinize the spatial effects, relative importance, and interactive impacts of two-dimensional and three-dimensional (2D/3D) built environments on land surface temperature (LST). The results indicate that: (1) 2D/3D variables exert significant effects on LST, with the cooling effect of the 3D green view index outweighing that of the 2D normalized difference vegetation index (NDVI). (2) The overall relative importance of 3D variables on LST is greater than that of 2D variables in both Chengdu and Chongqing. (3) The 3D variables have particularly strong impacts on LST in mountainous cities, which are 6.21 % higher than those in plain cities. (4) 2D/3D variables interactively influence LST. For instance, LST drops in Chengdu when floor area ratio (FAR) is above 1.5 and NDVI is below 0.53, as well as when FAR is less than 1 and NDVI is greater than 0.53. Our findings provide support and recommendations for location-specific sustainable urban development and effective heat adaptation strategies.