Refined urban canopy parameters and their impacts on simulation of urbanization-induced climate change

Changes in land cover and urban canopy structure caused by urbanization have important effects on regional climate. In this study, the Weather Research and Forecasting model is used to explore the influences of urbanization on local climate change in Guangzhou, a core city in the rapid urbanization region of the Pearl River Delta of China. Global Land Cover data from 2000 and 2018 are adopted to represent urban expansion, and urban canopy parameters (UCPs) established by a novel method are incorporated to represent changes in urban density. Model results reveal that the updated land cover and refined UCPs describe the surface information more accurately. The 10-m wind speed is reduced by 1-4 m/s and the 2-m air temperature is increased by 2-4 degrees C in urban areas, which brings the simulation results closer to observations. In terms of surface energy balance, upward longwave radiation is increased by 14.3 W/m(2) and the land surface temperature is increased by 0-25 k; hence the net all-wave radiation is decreased by 15.6 W/m(2). Meanwhile, the urban boundary layer height is increased by 192.2 m on average, but along with the decreased mean wind speed, the boundary layer ventilation is reduced by 500-3500 m(2)/s.