Exploring the impact of 2D/3D urban morphology on land surface temperature within the diurnal cycle in Tianjin

The urban heat island (UHI) effect not only impacts urban climates and residents' quality of life but also poses challenges to energy consumption and sustainable development in cities. While many studies have explored the relative importance and marginal effects of two-dimensional (2D)/ three-dimensional (3D) urban morphology on land surface temperature (LST) to mitigate UHI, the interactive effects of these 2D/3D morphology metrics on daytime and nighttime LST at different grid scales have been largely overlooked. This study focuses on the area within the outer ring of Tianjin, and analyzes the relative importance, marginal effects, and particularly the interaction effects of 2D/3D urban morphology on LST. Our findings reveal the following: (1) The normalized difference vegetation index (NDVI) has the most significant cooling effect across all variables and at all three grid scales. (2) NDVI and bare land coverage have the greatest impact on daytime LST, while building height and tree height (TH) predominantly influence nighttime LST. (3) The relationships between key 2D/3D metrics and LST are nonlinear. Overall, NDVI is negatively correlated with LST across all three grid scales. (4) Interactions between 2D/3D metrics affect LST; LST decreases when TH exceeds 1.8 m and building density is below 62%, or when TH is below 1.8 m and building density exceeds 62%. These findings provide valuable insights and recommendations for sustainable urban development and effective heat adaptation strategies in specific locations.