A REGIONAL SCALE-MODEL FOR OZONE IN THE UNITED-STATES WITH SUBGRID REPRESENTATION OF URBAN AND POWER-PLANT PLUMES

Emissions from urban and power plant sources are processed in generalized plumes where chemistry and dilution proceed for 8-12 hours before mixing with air in a large resolution element. A realistic fraction of pollutants reacts under high-NOx conditions, and NOx is removed significantly before dispersal. Results are compared with results from grid models that do not distinguish plumes and with observational data. Grid models with coarse resolution are found to artificially disperse NOx over rural areas, therefore overestimating rural levels of both NOx and O3. Regional net ozone production is too high in coarse grid models, because production of O3 is more efficient per molecule of NOx in the low-concentration regime of rural areas than in heavily polluted plumes from major emission sources. Ozone levels simulated by our model are shown to agree with observations in urban plumes and in rural regions. -from Authors