Modeling the contribution of long‐term urbanization to temperature increase in three extensive urban agglomerations in China

Abstract

AbstractThis study simulated the effects of changes in the underlying surface induced by long‐term urbanization on trends in surface air temperature (SAT) over three extensive urban agglomerations (Beijing‐Tianjin‐Hebei, BTH; the Yangtze River Delta, YRD; and the Pearl River Delta, PRD) in China during 1980–2009. To isolate the effects of continuous urban expansion on SAT with the least computation cost, we employed the Community Land Model (CLM4.5) in an off‐line mode for a relatively long period. Based on a high‐quality land use data set dating back to the 1980s, two scenarios were designed to represent the distributions of both nonurban and historically urban land use. By comparing the results of two numerical experiments, urban‐induced warming in daily mean SAT (Tmean) over the three urban agglomerations, BTH, YRD, and PRD, were found to be 0.13°C/30 yrs, 0.12°C/30 yrs, and 0.09°C/30 yrs, contributing about 9.70%, 10.3%, and 9.68% to the mean long‐term SAT trends, respectively. In addition, a higher contribution of urban‐related warming was found in winter for BTH and in summer for the other two regions. However, urban‐related warming had no significant effect on the trends of daily maximum SAT (Tmax) when compared with daily minimum SAT (Tmin). Specifically, at a local scale, the contributions of urban warming to the background warming in three representative cities, Beijing, Shanghai, and Guangzhou, were 12.7%, 29.0%, and 23.6%, respectively.