The Impacts of Urban Surface Expansion on Regional Climate over East Asia

Due to the fixed-in-time urban surface data in the commonly used regional climate models, the impacts of urban surface expansion on regional climate were not considered when performing long-term climate studies, especially in the areas with rapid economic development and intense anthropogenic activities. By incorporating satellite-based urban surface data for the past 30 years in China, the impacts of urban surface expansion on regional climate, especially on surface air temperature and precipitation, which is highly connected to the daily lives and activities of humans , were evaluated using the regional climate MM5V3 and WRFV3.4. The impact on SAT due to urban surface expansion between 1980s and 2010s revealed that annual urban-related warming was lower over East Asia and China, but higher in eastern China, which experienced dramatic urbanization. Greater warming could be detected over urban surface areas in the three city clusters in eastern China [Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD)], which reached up to 1.0°C. Further analysis showed that urban-surface-expansion-induced changes in albedo and the total cloud amount contributed to the changes in the radiation budget. Strong surface radiative forcings (greater than 10 W m⁻²) over urban areas were detected, which mainly resulted from the weaken upward shortwave flux. Meanwhile, there was further impacts on the large-scale circulation and precipitation, which was weakened in northeast and north China but intensified in east and south China.