Sensitivity of predicted pollutant levels to urbanization in China

摘要

Urbanization in China accompanies economic development and population growth. Changes in land use leads to changes in both meteorological and chemical fields. In this study, the impact of land use change in Jing-Jin-Ji (JJJ, indicating Beijing-Tianjin-Hebei) and Yangtze River Delta (YRD) areas on meteorology and ozone concentrations are studied using the WRF-Chem model. Land use change is represented by two different land cover data sets: USGS and MODIS. Monthly-average simulations show that urbanization causes an increase in 2-m temperature by maximum 2.4 ℃ and 3.2 ℃ in these two areas, respectively. Wind speed simulations suggest a decrease (average 1.2 m s~(-1)) in daytime for YRD, and in nighttime forJJJ. Dew point differences show a dry effect over both areas, with maximum -3 ℃ in JJJ and -2.4 ℃ in YRD. Planetary Boundary Layer (PBL) height increases by 400 m (maximum in JJJ) and 600 m (maximum in YRD) for daytime, and nighttime increases are less than 100 m. Daytime ozone concentrations in JJJ increase by 20 ppb due to urbanization, while in YRD the difference is around 5 ppb. Compared to observations, mean errors in urban areas was improved when using updated land use information by 14.2% and 35.6%, and in suburban areas by 5.8% and 10.7%. Updating land use data set in air quality modeling is important in application to regions with rapid urbanization such as China. The effects due to land use change can be as large as those due to 20% increase in emissions.