Comparison of CMAQ Predicted Ozone Concentrations with Remotely Sensed Data

The performance of air quality models are typically evaluated against atmospheric pollutant concentrations obtained from ground-based observations. In this study, the model predicted ozone (O3) columnar concentrations are compared with Tropospheric Ozone Residual (TOR) data estimated from satellite products (Fishman and Balok, 1990; Wozniak et al., 2005). Predicted O3 concentration profiles are obtained from the Community Multiscale Air Quality (CMAQ) model developed by the United States Environmental Protection Agency (USEPA). The TOR uses differences between Earth Probe Total Ozone Mapping Spectrometer (EP-TOMS) derived total column ozone (TCO) and the empirically corrected nadir viewing Solar Backscatter Ultraviolet (SBUV) stratospheric column O3. Air quality model simulations are performed using the CMAQ model for selected days during the summer period of year 2001. The modeling domain covers the continental U.S. with a 36-km grid and a 24-layer vertical resolution. Model ready emissions for the summer period of 2001 are obtained from the USEPA National Emissions Inventory. The model predicted ozone concentrations are integrated up to the top of the atmosphere and compared with the TOR data for the entire summer period of year 2001. CMAQ derived O3 concentration profiles are also compared with ozonesonde data obtained from three operational U.S. sites at Wallops Island, VA., Boulder, CO, and at the University of Alabama at Huntsville, AL. Modeled effects of natural and anthropogenic chlorine emissions on atmospheric ozone concentrations have been recently reported. The chlorine emissions were found to affect the ground level concentrations of O3 near the Salt Lake, UT, and at Houston, TX. Using the TOR product, we will evaluate the CMAQ model predicted tropospheric O3 columnar concentrations in these two areas during July 18-21, 2001. This study will provide a preliminary assessment of how well the CMAQ columnar O3 compare with those observed using satellites and to determine whether O3 predictions agree better with observational products with or without the inclusion of chlorine chemistry.

DISCLAIMER

The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.