The Urban Airshed Photochemical Grid Model has been applied to a data base assembled for the Philadelphia metropolitan area consisting of meteorological and air quality data collected during the EPA 1979 summer field study and a spatially, temporally, and chemically resolved emissions inventory of hydrocarbons and nitrogen oxides. The report presents results of (1) the evaluation of Urban Airshed Model performance on 2 selected model test days, (2) application of the Urban Airshed Model for control strategy planning, and (3) sensitivity tests to determine the response of Urban Airshed Model predictions and control requirements to uncertainty in background concentrations. The model tended to slightly overestimate calculated hourly ozone for both simulation days; but performed well in replicating observed concentrations. Results indicate that urban hydrocarbon emission reductions required to attain the National Ambient Air Quality Standard (NAAQS) for ozone vary widely depending on assumed levels of background hydrocarbons and ozone standard. Therefore, all large metropolitan areas in the Northeast must cooperate to reduce emissions if region-wide attainment of the ozone standard is to be maintained.

"Systems Applications, Inc." Distributed to depository libraries in microfiche. "June 1985." "EPA/450-4-85-003." U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Monitoring and Data Analysis Division (MD-14). Contract Number: 68-02-3870. Includes bibliographical references (pages 183-188).