Regional Climate Change Induced by Land-Use Change and Implications for Air Quality in the Pearl River Delta, China

The Pearl River Delta (PRD) region, located in the southern part of Guangdong Province in China, has experienced remarkable economic development and urbanization in the past two decades. Urban areas now account for 60% of the total land use in PRD, and significantly modify local and regional weather and climate, and hence impact air dispersion and quality. In this paper, the Weather Research and Forecasting model (WRF) model, coupled to urban and biogenic-emission models, is used to explore impacts of land-use change on regional climate and its implication on air quality. Two scenarios of land-use maps are used to represent early 1990s (prior to urbanization, NU) and today's urban distribution in the PRD (HU). Monthly simulation results for October 2004 show distinct differences in shelter-level temperature, humidity, surface fluxes, height of planetary boundary layer (PBL), and wind fields with the above land-use scenarios. The maximum difference in simulated monthly mean temperature over urban areas was 0.9°C. A larger temperature difference was found in urbanized area of Guangzhou, Dongguan, Zhongshan and Shenzhen. The monthly mean relative humidity in urban areas decreased by 1.4% as a result of urban expansion. The maximum decrease in mixing ratio was 0.4 g kg-1 in Guangzhou and Dongguan, reducing relative humidity about 2.4%, and the increase in mean height of PBL is roughly 180 m over urban areas. We will present analysis based on these simulations and a yearlong simulation for 2004 with regard to relationships between surface air temperature and downward solar radiation, precipitation frequency, stagnation events, and ventilation modified by urbanization and implications to high-pollution events in PRD.