Urban core greening and industrial decentralization lead to contrasting trends in surface urban heat islands in a metropolitan area in China

Surface urban heat islands (SUHI) in urban agglomerations display diverse spatiotemporal patterns, particularly in rapidly urbanizing regions, where these patterns are not well understood. This study examined the spatiotemporal trends of SUHI intensity (SUHII) on the west bank of the Pearl River Estuary, China, from 1990 to 2020, focusing on spatial variations within urban core (UC) and urban expansion (UE) areas and their driving mechanisms. Results show that urban areas expanded rapidly, leading to the formation of a regional heat island, with SUHI intensity varying across the region and the hottest areas shifting from the UC to the UE. In the UE, SUHII increased significantly due to farmland conversion to impervious surfaces and a decline in the Normalized Difference Vegetation Index (NDVI), driven by industrial suburbanization. In contrast, SUHII in the UC exhibited a marked decline, attributable to increased vegetation greening and urban renewal initiatives. These findings reveal long-term trends in SUHI evolution and underscore the significant impact of industrial decentralization and urban renewal on the SUHII dynamics. The study provides critical insights for urban planning and strategies to mitigate SUHI in metropolitan regions.