TOWARD A CHEMICAL CLIMATOLOGY OF OZONE CONTRIBUTIONS FROM LONG RANGE TRANSPORT IN THE PACIFIC NORTHWEST -- INCORPORATION OF OZONE TRACERS IN THE AIRPACT-4 AIR QUALITY FORECAST SYSTEM

Air-quality modeling is an important tool for evaluating strategies for complying with the NAAQS. Two perennial issues of interest are the effects of long-range transport (LRT) and of stratospheric ozone intrusion (SOI) on air quality. Under the EPA Exceptional Events Policy, for example, a nominal exceedance can be excluded from design value calculation if it can be credibly ascribed to long-range transport or stratospheric ozone intrusion. Air-quality modeling is potentially an appropriate tool for attempting demonstration of LRT and SOI in making a case for Exceptional Event status for an exceedance. Also, ample evidence exists that local air pollution should sometimes be viewed in the context of a baseline pollution levels, and that these baseline levels are influenced by LRT and SOI (Wigder et al., 2013).