Evaluation of AIRPACT-2, a numerical, photochemical air quality forecast system, for ozone, particulate matter (PM2.5), and selected air toxics in the Pacific Northwest

AIRPACT-2 is an enhanced web-based air-quality forecasting system based on the MM5 meteorological model coupled with a dynamic emissions processing system and the CALMET/CALGRID photochemical grid modeling pair. The system reports hourly concentrations of pollutants for the Pacific Northwest region covering an area from Vancouver, BC in the north to Salem, OR in the south, and from the Pacific coast in the west to beyond the crest of the Cascade Mountain Range in the east.

This paper presents a performance evaluation of the AIRPACT-2 modeling system results in comparison against observed concentrations of ozone (O3), particulate matter (PM2.5), and some selected air toxics species, including formaldehyde, acetaldehyde, 1,3-butadiene, benzene and perchloroethylene. The model performance for September, 2003, has been analyzed in terms of statistical measures including peak to mean ratio, bias, normalized bias, gross errors and normalized gross errors. The evaluation also emphasizes analysis of the accuracy of the emission inventories used in AIRPACT-2. The hourly observed concentrations of ozone and particulate matter (PM2.5) were collected through a network of surface monitoring stations and provided by the Washington Department of Ecology, and observed concentrations of selected air toxics species were obtained from the EPA Pilot Cities Program.