CMAQ Modeling of SHARP 2009 Episodes

Photochemical modeling of ozone formation in the Houston area generally underestimates the concentrations of free radical precursors contributing to ozone formation. There are unresolved questions about the quantitative contribution of direct emissions and of atmospheric reaction products to the formation of compounds that are related to the free radical chemistry, and ultimately, its role in Houston's ozone production. Here we present preliminary modeling results of a few selected SHARP 2009 episodes using the Weather Research Forecast model and the Community Multiscale Air Quality model (WRF-CMAQ) to analyze chemical processes, including process analysis studies along trajectories linking a site at the Houston Ship Channel and the University of Houston Moody Tower site. Furthermore, WRF-CMAQ results will be shown to elucidate the relative importance of photolysis of ozone, nitrous acid (HONO), formaldehyde (HCHO) and hydrogen peroxide (H2O2) as radical sources in the Houston atmosphere.