Urbanization effects on vegetation and surface urban heat islands in China's Yangtze River Basin

Abstract

In the context of rapid urbanization, systematic research about temporal trends of urbanization effects (UEs) on urban environment is needed. In this study, MODIS (Moderate Resolution Imaging Spectroradiometer) land surface temperature (LST) data and enhanced vegetation index (EVI) data were used to analyze the temporal trends of UEs on vegetation and surface urban heat islands (SUHIs) at 10 big cities in Yangtze River Basin (YRB), China during 2001-2016. The urban and rural areas in each city were derived from MODIS land cover data and nighttime light data. It was found that the UEs on vegetation and SUHIs were increasingly significant in YRB, China. The δEVI (the UEs on vegetation, urban EVI minus rural EVI) decreased significantly (p < 0.05) in 9, 7 and 5 out of 10 cities for annual, summer and winter, respectively. The annual daytime and nighttime SUHI intensity (SUHII; urban LST minus rural LST) increased significantly (p < 0.05) in 10 and 4 out of 10 cities, respectively. The increasing rate of daytime SUHII and the decreasing rate of δEVI in old urban areas were much less than the whole urban area (0.034 °C/year vs. 0.077 °C/year for annual daytime SUHII; 0.00209/year vs. 0.00329/year for δEVI). The correlation analyses indicated that the annual and summer daytime SUHII were significantly negatively correlated with δEVI in most cities. The decreasing δEVI may also contribute to the increasing nighttime SUHII. In addition, the significant negative correlations (r < -0.5, p < 0.1) between inter-annual linear slope of δEVI and SUHII were observed, which suggested that the cities with higher decreasing rates of δEVI may show higher increasing rates of SUHII.