Numerical Simulation of Urbanization Climate Effects in Regions of East China

To explore effects on summer climate from land use changes in various metropolitan areas and the possible mechanisms, an atmospheric general circulation model (LMDZ) developed by the French dynamic meteorology laboratory was used. East Asia climate change induced by land use changes in the Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei metropolitan area were simulated by the LMDZ. Results showed that changes of the underlying surface type in the Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei metropolitan area significantly reduced the surface latent heat flux. In order to balance the surface energy budget, the ground temperature increased and the sensible heat flux and surface effective long-wave radiation were enhanced. The surface energy budget was re-equilibrated with an elevation of the surface temperature. The main changes were situated in areas of modified underlying surface type. The temperature response has a significant local characteristic. Among the different areas, there was a good relationship between the regional surface temperature change and changes in surface heat flux. Changes in the total heat flux of the Yangtze River and Pearl River Deltas were much greater than those in the Beijing-Tianjin-Hebei metropolitan zone. Local warming of the Yangtze River and Pearl River Deltas were also more than doubled in the Beijing-Tianjin-Hebei metropolitan zone. Although a local temperature increase is favorable to a thermal low pressure and induces significant upward motion in the lower layers of the atmosphere, the decrease in evaporation significantly reduces the local water vapor decreasing precipitation. In fact, the change in moisture conditions was the primary factor contributing to the precipitation reduction. Since the geopotential height field in high layers exhibited negative anomalies in the north and positive anomalies in the south, the Western Pacific Subtropical High extended westward and strengthened. As such precipitation reduction was not limited to local areas, but extended to large zones in the eastern part of the domain. This was particularly true in the three-area combined experiment.