Research on Time Series and Spatial Gradient of Urban Heat Island Expansion from the Perspective of Urban Renewal

Currently, urban heat island (UHI) has evolved beyond being a homogeneous climate and environmental issue, it has emerged as a critical threat to the sustainable development of urban environment. This study highlights substantial spatio-temporal expansions of UHIs in China between 2005 and 2020. Notably, the UHI intensity (UHII) exhibited a more pronounced increase during nighttime than daytime, with land surface temperature rises of 0.46 °C and 0.17 °C, respectively. Analysis of 48 representative cities revealed that although most cities experienced a faster UHII growth rate in new UHIs compared with pre-existing ones, the significant initial disparity hinders the new UHIs in 2010 and 2015 from catching up with the UHII of pre-existing UHIs in the short term. However, by 2025, it is projected that the daytime UHII of new UHIs in 2015 will surpass that of new UHIs in 2010 in 21 cities, while the same trend is expected in 31 cities during nighttime. Furthermore, spatial gradient analysis unveiled individual variations in UHII within different buffer rings. These findings provide valuable insights into the spatial expansion and dynamics of UHIs in China, contributing to the understanding of UHI effects. Moreover, these findings can inform urban renewal strategies aimed at mitigating UHI's adverse impacts, enhancing urban resilience, and fostering the development of sustainable and livable cities.