Long-Term and Multi-Index Assessment of Urban Thermal Environments Across Local Climate Zones: A 20-Year Analysis of Xiamen, China

The Local Climate Zone (LCZ) provides a systematic approach for analyzing the differences in urban thermal environment. However, given the scarcity of accessible multi-year LCZ maps, studying the long-term thermal differences among LCZs remains challenging. This study classified LCZs using multi-year remote sensing imagery of Xiamen and analyzed the thermal differences among them. The results indicate that (1) the land surface temperatures (LSTs) of LCZ(8) Large low-rise and LCZ(10) Heavy industry are the highest, while the LSTs of LCZ(A) Dense trees and LCZ(G) Water are the lowest. Among compact LCZs(1,2,3), the LST of LCZ(1) Compact high-rise is consistently lower than that of LCZ(2) Compact mid-rise and LCZ(3) Compact low-rise. (2) The thermal contribution indices of built-up LCZs are positive, whereas those of land-cover LCZs are negative. The thermal contribution indices of LCZ(2) Compact mid-rise, LCZ(3) Compact low-rise, and LCZ(10) Heavy industry show a continuous annual increase, while the thermal contribution indices of LCZ(9) Sparsely built, LCZ(A) Dense trees, and LCZ(G) Water show a consistent annual decrease. (3) In terms of the thermal environment regulation demand index, LCZ(1) Compact high-rise, LCZ(2) Compact mid-rise and LCZ(3) Compact low-rise have the highest thermal environment regulation demand. By integrating long-term LCZ mapping with LST, TCI, and TERDI, this study provides a multidimensional and planning-oriented framework for urban thermal environment assessment and targeted mitigation.