Illinois State Water Survey - CAQIMS - Components, University of Illinois at Urbana-Champaign

A Basis for Achieving Economic, Societal and Environmental Goals in Illinois
Xin-Zhong Liang

Air Quality Model (AQM)
The air quality model (AQM) is the most advanced version of the SAQM (Chang et al. 1997) that was originally developed for study of the elevated O3 problem in the central valley of California (Ranzieri and Thuillier 1991). The SAQM incorporates significant improvements over the EPA RADM2 developed under the National Acid Precipitation and Assessment Program (Chang et al. 1990). These improvements include new numerical algorithms for tracer advection and gas-phase chemical reactions, additional gas-phase chemical mechanisms, an updated dry deposition parameterization, new nesting procedures, and a better representation of near-surface processes. Important updates of AQM, relative to the SAQM, include an efficient gas-phase chemistry solver (Huang and Chang 2001), and the EPA regional particulate submodel (Binkowski 1999). The AQM has multiple choices for the chemical mechanism, including RADM2 (Stockwell et al. 1990), CB4 (Gery et al. 1989), and SPARC (Carter 1990). The AQM has been successfully coupled with the CMM5 (Liang et al. 2004b) and SMOKE (Houyoux et al. 2000; Williams et al. 2001) for continuous long-term climate-air quality applications.

The future AQM development will focus on coupling the CMAQ with the CWRF (Liang et al. 2004a). This will incorporate a new chemical mechanism RACM (Stockwell et al. 1997) and an improved particles module.

Air Quality Simulation Using the CMM5 meteorology and SMOKE emission data, the AQM air quality simulation of 1995 summer was performed. Figure 1 shows the ozone concentration over the Eastern United States at 1995 July 11 16Z CST and July 12 16Z CST. St. Louis, Milwaukee, and Chicago experienced elevated ozone ranged from 100 to 120 ppb for the period of July 11-14. Figure 2 compares the observed and simulated hourly ozone concentration variations for June 1995 in the St. Louis area.

 
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