A New Way To Model Urban Air Pollution
Urban regions account for an increasing fraction of global air pollutants, but urban-scale aerosol processing is not included in global atmospheric models due to the computational demands of modeling at such detailed temporal and spatial scales. Now, a DOE team from the MIT Joint Program on the Science and Policy of Global Change has developed a detailed air quality meta-model that includes this processing. This urban processing model was used in a global 3-D chemical transport model to simulate the effects of cities around the world on aerosol chemistry, physics, and radiative effects at the global scale. The study compares the new method with the traditional approach of diluting total aerosol emissions across global model grid cells, which does not capture the heterogeneity of urban and non-urban areas within each grid cell. The researchers found that the urban processing model predicted a lower concentration of atmospheric aerosols than the dilution method, particularly in the Northern Hemisphere and during the summer season. In addition, the urban processing model showed increased concentrations of primary aerosols, like black carbon and organic carbon, and decreased concentrations of secondary aerosols, like sulfates. The results show that the traditional dilution method leads to significantly more negative aerosol radiative forcing compared to results that include detailed urban-scale processing.
Cohen, J. B., R. G. Prinn, and C. Wang. 2011. “The Impact of Detailed Urban-Scale Processing on the Composition, Distribution, and Radiative Forcing of Anthropogenic Aerosols,” Geophysical Research Letters 38, L10808. (DOI: 10.1029/2011GL047417)