Effect of Urban Built-Up Area Expansion on the Urban Heat Islands in Different Seasons in 34 Metropolitan Regions across China

The urban heat island (UHI) refers to the land surface temperature (LST) difference between areas and their undeveloped or underdeveloped surroundings. It is a measure of thermal influence built-up area expansion (UBAE), topic that has been extensively studied. However, impact UBAE on LST differences rural (UHIU−R) emerging (UHIU−S) in different seasons seldom investigated. Here, UHIU−S UHIU−R 34 major metropolitan regions across China, spatiotemporal variations based long-term space-borne observations during period 2001–2020 were analyzed. quantified by landscape metrics 2020 2000 UHI was further impacted level economic development topography. cities located more developed significant than less regions. Coastal experienced most obvious UBAE, followed plain hilly cities. mountainous weakest. On an annual basis, larger UHIU−S, decreasing slowly with UHIU−S. In seasons, larger, clearly varying temporally summer winter, temporal significantly correlated but not winter. seasonal Both coastal lowest summer, fastest while those mountain decreased slowest. change density lands primary driver affecting changes proportion shape, speed smallest, all which can reduce UHI. These findings provide new perspective for deeper understanding effect seasons.