Optimizing Internal-External Land Function Allocation to Mitigate Urban Heat Islands: Insights from Hong Kong

Land function types exhibit varying heat performances, influenced by their external neighborhood environments. Jointly allocating internal and external land functions may offer a sustainable urban management strategy to mitigate urban heat islands (UHI), though the related research is limited. To address this gap, we focused on Hong Kong, using land surface temperature (LST) as a climate indicator to explore the impact of internal and neighboring land function zones on surface heat conditions. First, we quantified the internal and external environments, internal-external interaction degree, and the internal land function mixing level using a reality-based spatial quantification method. Second, we employed a Lasso regression model to investigate how land function features influence LST. Third, we used ANOVA and variance partitioning to identify the contributions of internal land functions and the largest neighboring land functions to LST. The results indicate that (1) Internal land function types significantly affect LST. Industrial areas have the highest LST, followed by residential/office and transportation areas, while vegetation and water bodies exhibit lower LST. Proximity to industrial or transportation areas raises LST, whereas surrounding vegetation cools it. (2) ANOVA and variance partitioning reveal that internal land functions account for 49.8% of LST variation, main surrounding functions for 2.8%, and their interactions for 3.5%. (3) The interaction impacts vary across different internal-external function combinations. Oceans particularly cool residential and office areas, while vegetation is more effective for industrial and transportation zones. Conversely, artificial land uses, especially industrial and transportation areas, significantly increase internal area temperatures. (4) Areas with complex shapes and higher internal mixed levels show lower LST, suggesting that increased interaction with external surroundings and greater diversity of land functions can reduce LST. These findings are crucial for urban planners aiming to mitigate UHI through sustainable design, particularly in mixed-function zones and urban-rural transition areas.