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Predicting Ozone in the Colorado Front Range using EPA’s Air Quality Model
Citation:
Matichuk, R., C. Hogrefe, G. Tonnesen, R. Gilliam, S. Napelenok, Bill Hutzell, D. Kang, J. Bash, R. Mathur, G. Pouliot, Keith Wyat Appel, G. Pierce, K. Briggs, AND K. Shonkwiler. Predicting Ozone in the Colorado Front Range using EPA’s Air Quality Model. 19th Annual CMAS Conference, N/A, NC, October 26 - 30, 2020.
Impact/Purpose:
This abstract describes the design and application of an air quality modeling platform instrumented with CMAQ’s ISAM source apportionment capability to study ozone exceedances in the Denver Metro/North Front Range (DMNFR) ozone nonattainment area (NAA). The work results from a R2P2 collaboration between Rebecca Matichuk of Region 8 and CEMM’s Atmospheric and Environmental Systems Modeling Division.
Description:
The Denver Metro/North Front Range (DMNFR) ozone nonattainment area (NAA) in Colorado has had unhealthy levels of ozone for the past decade. State and national air quality programs have focused on reducing the emissions of volatile organic compounds (VOCs) and nitrous oxides (NOx), both of which are precursors to ozone formation, to address the elevated ozone in this area. It is speculated that the effects of these emission reductions may be partially offset by increasing levels of background ozone and increases in local emissions from population growth and extensive oil and gas development in the area. Background ozone includes contributions from wildfires, biogenic emissions, lightning NOx emissions, international anthropogenic pollution, and stratospheric intrusions. A collaborative effort among EPA Region 8, the Office of Research and Development (ORD), the Office of Air Quality Planning and Standards (OAQPS) and the Colorado Department of Public Health and Environment (CDPHE) have developed a hemispheric-to-regional scale air quality model platform to simulate the transport and chemistry of ozone in the DMNFR NAA in Colorado and to estimate source contributions to simulated ozone. The platform uses the Weather Research and Forecasting (WRF) model and EPA’s 2014 National Emissions Inventory (NEI) and the latest Community Multiscale Air Quality (CMAQ) model that includes the Integrated Source Apportionment Method (ISAM). This study focuses on July and August 2014 to align with two Colorado field studies that provided an extensive set of measurement data to evaluate the air quality model platform. This study assesses model performance through a comprehensive evaluation and detailed comparisons with measurements of meteorological variables, ozone, and ozone precursor species from a variety of surface, airborne and mobile platforms. Initial results show that the CMAQ model is biased low for ozone and its precursors during high ozone episodes. ISAM results for both the regional and hemispheric scale simulations are analyzed to quantify the contributions of various anthropogenic and natural emission sources to simulated ozone in the DMNFR, particularly during high ozone episodes.
