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Atmospheric Modeling and Analysis Research

Research in Action

Community Modeling and Analysis System (CMAS)


Air pollution doesn’t stay still – after leaving its source, it can travel across counties, states, countries, and even continents and oceans. This makes modeling air quality a difficult and complex problem, and one that requires regionally- and even globally-coordinated efforts to solve.

The models to assess these problems and evaluate alternative solutions are increasingly complex. Many focus on modeling just one pollutant. To address this issue, EPA researchers developed a modular, multi-scale, multi-pollutant system that can link a variety of models together. The system was designed to be a community modeling system, meeting the needs of a wide range of users as well as eliciting their suggestions and contributions. In order to be ongoing and viable, the system needed a mechanism for facilitating feedback from users and for updating models to reflect user contributions.


In order to provide community air quality modeling support, sharing of ideas and techniques through communication, and to encourage the growth of the community, EPA instituted the Community Modeling Analysis System (CMAS) Center in 2001, currently operated under contract by the University of North Carolina at Chapel Hill’s Institute for the Environment.

The CMAS Center has two main goals: First, to improve environmental managers’ ability to evaluate the impact of air quality management strategies for multiple pollutants at multiple scales (local, regional, national), and second to improve scientists’ ability to probe, understand, and simulate chemical and physical pollutant interactions in the atmosphere. As such, CMAS serves as a resource for the widespread application of air quality models and for their continued scientific advancement.

The center provides free support to new and established users of EPA air quality modeling products via the Web, e-mail listserv and phone. CMAS also provides user training for modeling tools on a fee basis. The training is offered in CMAS offices and at user offices, and has been held in various locations throughout the United States, Asia, Europe and South America. Additionally, CMAS co-sponsors an annual CMAS Conference funded by registration fees. EPA air quality modeling software supported by the Center include the:

Results and Impacts

CMAS has been highly successful in expanding the air quality modeling community and providing support and information to participants in governments, academia and commercial communities worldwide. Online support is provided through three active listserves: M3User for community technical discussions; M3List as a forum for announcements of new releases, bug fixes, conferences; and Emregional for emission modeling. Users can visit the CMAS support website to download multiple versions of the air quality modeling products, including documentation. Since the website’s inception, there have been approximately 45,000 modeling product downloads, including about 9,000 in 2011.

The growth of the user community has helped the annual CMAS Conference become an anticipated event that highlights EPA’s most recent air quality modeling product developments and applications, and provides a forum for model developers and users to share information and ideas for model improvement. The conference has grown in attendance to reflect the spread of the use of CMAQ tools, and is now attended by modelers from more than 25 countries.

The annual conference also provides a forum for EPA atmospheric modeling scientists to present their most recent research and receive valuable scientific feedback. The conference often includes a special session focusing on a topic of interest to modelers, such as air quality model development, air quality forecasting, or air quality model evaluation. These special sessions have led to special journal issues, further raising the profile of the conference.

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