Effect of emissions control programs on visibility in southern California

A new method for the analysis and display of the effect of emissions controls on visibility is applied to conditions in southern California. An advanced mechanistic air quality model that represents airborne particles as a source-oriented external mixture first is used to track emissions source contributions to the size distribution and chemical composition of airborne particles at Claremont, CA, under heavy smog conditions. The resulting description of the aerosol is used in a Mie scattering calculation to determine the magnitude and particle size dependence of light scattering and absorption in the atmosphere. The resulting light scattering and absorption coefficient values are supplied to an image processing-based visibility model that creates full color representations of the appearance of the local terrain in the presence of the specified level of air pollution based on satellite-generated landscape images. By linking these models, a direct connection is established between source emissions and resulting visual air quality. The composite modeling system then is used to studythe effectthat different emissions control strategies would have on visibility in southern California. An aggressive program of 92 specific emissions control measures that include primary particle controls plus controls on reactive gases that act as secondary aerosol precursors would more than double visual range at Claremont under the 1987 historical conditions studied. Synthetic landscape images show that the mountains to the north of Claremont that are not visible at a range of 10 km under base-case conditions would be visible if the emissions controls described above were applied.