PNNL

Abstract

The impact of urbanization-induced land-cover change and increase in anthropogenic emissions on the air quality of the megacity cluster of the Yangtze River Delta (YRD) is investigated using the WRF-Chem model coupled with an Urban Canopy Model at cloud-resolving resolution. The urban land-cover effect results in considerable reduction of near-surface aerosol concentrations over urban regions and an increase in particle concentrations at higher altitudes over the surrounding rural areas. The UHI effect increases the lower atmospheric instability and vertical velocity, thus increasing the planetary boundary layer height and ventilation over the urban area, favoring the dispersion of pollutants from urbanized areas to their immediate vicinities. However, the urbanization-induced increases in aerosol emissions outweigh that of land-cover change, resulting in a net increase in surface particle concentrations by up to 50 µg m -3 and the occurrence of winter haze by more than 10 d season-1 in the YRD region.