Abstract: Remote sensing technology can objectively and quantitatively evaluate the spatial and temporal variations of surface urban heat island intensity. Analyzing the influencing factors of urban heat islands could provide effective scientific references for urban ecological construction. Based on the GEE (Google Earth Engine) platform, we estimated the surface urban heat island intensity in the Yangtze River Economic Zone from 2003 to 2019 using long time series of MODIS satellite data. We evaluated the ecological environment using urban thermal field variance index, and analyzed the causes of urban heat islands using geographical detectors. The results showed that mean annual temperature of the five urban agglomerations in the Yangtze River Economic Zone during 2003-2019 was 22.78 ℃, with 23.91 ℃ on daytime, 7.59 ℃ at nighttime, and an overall increasing trend of 0.02, 0.02 and 0.006 ℃·a^-1, respectively. The five urban agglomerations in the Yangtze River Economic Belt had the highest proportion of heat island free during 2003-2019, followed by weak heat islands and weak cold islands, and the lowest proportion of strong heat islands. The urban heat island effect showed a decreasing trend throughout the year, during the day, and at night. The overall environmental quality of the Yangtze River Economic Zone was excellent. Geographic detector for factor detection showed that DEM, land-cover type, and O₃ were the main drivers for surface urban heat island effect in the Yangtze River Delta urban agglomeration. Evapotranspiration, ultraviolet aerosol index, and population density were the main controlling factors of surface urban heat island effect in the middle reaches of the Yangtze River urban agglomeration. Normalized difference vegetation index, nighttime light index, and land-cover type were the main controlling factors for surface urban heat island effect in the Chengdu-Chongqing urban agglomeration. Normalized difference vegetation index, DEM, and CO were the main controlling factors of surface urban heat island effect in the central Guizhou urban agglomeration. Evapotranspiration, O₃ and normalized difference vegetation index were the main controlling factors of surface urban heat island effect in the central Yunnan urban agglomeration.

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