Polycentric structure and urban thermal environment: A large-scale study from multi-perspectives

Polycentric development is a widespread tendency, and urban thermal environment is unavoidably changed in this context. Using data from 265 Chinese cities, we explore urban thermal environment under polycentric development from three perspectives. First, we analyze the correlation between three metrics describing polycentricity and surface urban heat islands (SUHI) at the urban scale, taking into account diurnal and seasonal differences. Second, we examine the surface temperature difference between the main center and subcenter(s) as well as its possible influencing factors. Third, we use structural equation modeling to quantitatively confirm the mechanism behind the relationship between polycentric structure and SUHI. The results show that: (1) There is a significant positive correlation between polycentricity and daytime SHUI, regardless of the season. However, the relationship is insignificant during summer nighttime, and it even becomes negative during winter nighttime. (2) The majority of the main centers experience more severe thermal challenges. (3) Climate, urban size, vegetation, and industry are the mediators of the relationship between SUHI and polycentric structure during summer daytime. Our findings provide valuable insights for understanding thermal environment under polycentric development and can be used as a reference for proposing thermal mitigation strategies for cities that are or are becoming polycentric.