A performance evaluation of the 2005 release Models-3 CMAQ

The Clean Air Act and its Amendments require that the United States Environmental Protection Agency (EPA) establish National Ambient Air Quality Standards (NAAQS) for ozone and particulate matter and to assess current and future air quality regulations designed to protect human health and welfare. The most reliable tools for performing these assessments are air quality models, like EPA's Models-3 Community Multiscale Air Quality model (CMAQ). CMAQ is an Eulerian grid model that simulates concurrently the atmospheric and land processes affecting the transport, transformation and deposition of air pollutants and their precursors on both regional and urban scales. CMAQ performs these simulations following first principles and employs a “one atmosphere” philosophy that manages the complex interactions among multiple atmospheric pollutants including ozone, particulate matter, airborne toxics and acidic and nutrient species. As with any model, CMAQ requires evaluation against observational data to determine its value to the air quality and regulatory communities. Accordingly, a full, one year simulation will be performed for the contiguous U.S using the 2005 release of CMAQ that will be evaluated against observations from numerous networks including: the Air Quality System (AQS); the Clean Air Status and Trends Network (CASTNet) and the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network. Numerous statistical metrics and graphics will be used in this evaluation, including summary statistics, least squares coefficients and several measures of bias and error.