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Community Multiscale Air Quality Modeling System (CMAQ)

CMAQ User Community

CMAQ and its data products are used by a variety of private, academic, and governmental institutions in the United States and abroad. Because the model is both detailed and comprehensive, it is applied by professionals with a wide range of motivation and training. See below for many examples of how CMAQ contributes to better air quality in the United States and elsewhere.


Institutions Using CMAQ

Below are a few select examples of how the CMAQ model system is used in various government agencies, academic institutions, and private sector organizations.


Centers for Disease Control and Prevention (CDC)

The CDC use national air quality characterizations of ozone and PM2.5 based upon spatially fused surfaces that combine CMAQ results with ambient monitoring data to inform their  National Environmental Public Health Tracking Network (EPHT). Since 2002, EPA has collaborated with the CDC on the development of the EPHT Network.  The EPHT is a multidisciplinary collaboration that involves the ongoing collection, integration, analysis, interpretation, and dissemination of data. The network supports the linkage of air quality data with human health outcome data for use by various public health agencies throughout the U.S.  Specifically, CMAQ is used in the “Downscaler” model developed by the EPA, which uses a statistical approach to combine monitoring data in areas where monitors exist, and CMAQ output in areas without monitors.  These data can be used to inform the public of ozone and PM2.5 concentrations, like annual level or days above the regulatory standard, at the county scale. 

Related information:

EPA's EnviroAtlas

EnviroAtlas is an interactive resource “for exploring the benefits people receive from nature”, which are important but often overlooked. These benefits are termed “ecosystem goods and services.” EnviroAtlas uses CMAQ data specifically to display and understand the spatial patterns of deposition for different chemical compounds. This information can be combined with other EnviroAtlas data to examine different ecological processes.  

EPA's Office of Air Quality Planning and Standards

At federal, state, and local agencies, CMAQ is often used when developing regulatory policies because it represents the state-of-the-science in air quality modeling. A few examples of how CMAQ has been used for regulatory support can be found at CMAQ's Support of EPA's Mission web page.

National Weather Service's Air Quality Forecast

The National Weather Service (NWS) uses CMAQ to produce air quality forecasts twice daily. They have been producing these forecasts since 2004. The goal is to generate forecasts “with enough accuracy and advance notice to take action to prevent or reduce adverse effects.”

US Global Change Research Program (USGCRP)

The USGCRP released a document in April 2016 examining “The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment.”  CMAQ was used to estimate future ozone impacts from two separate regional climate simulations (see how CMAQ can be used to predict how climate change can affect air quality).  See Chapter 3 of the assessment for further details.

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State and Local Environmental Agencies

NC Department of Environmental Quality (NC DEQ)

The NC DEQ Division of Water Resources used CMAQ in 2009 for their Falls Lake Watershed Analysis Risk Management Framework (WARMF) development. CMAQ was used in the calculation of deposition into Falls Lake for different simulation scenarios on a seasonal or annual basis. The 2009 WARMF was used as a foundational element for the development of the Falls Lake strategy. A 2015 report was then used to evaluate the interim success of the strategy in achieving water quality goals, and successive versions of CMAQ were used to estimate improvements in atmospheric deposition of nutrients from the strategy’s baseline period.  

State Implementation Plan (SIP)

When EPA establishes a new National Ambient Air Quality Standard (NAAQS) or revises an existing NAAQS, it must designate areas as meeting (attainment) or not meeting (nonattainment) the standard. The Clean Air Act (CAA) requires states to develop State Implementation Plans (SIPs): a plan to attain the standards for each area designated nonattainment for a NAAQS.  

An important component of many SIPs is an attainment demonstration. This is a demonstration, most often using air quality modeling, which shows how states will attain the NAAQS in a future year. Many states have used CMAQ and other air quality models to support their attainment demonstrations. Models are used to determine which emissions control measures are needed to improve air quality to a level that meets the standards by CAA mandated deadlines. Below are a few examples of SIPs that have used CMAQ.

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University research

CMAQ is used by several academic institutions world-wide to conduct research in several topic areas. Research within academic institutions is often funded by national, state, or local government agencies. Some of that research includes:

  • Improving the modelled interaction of pollutants by considering the outcomes of "chamber studies" (where pollutant reactions are measured at controlled temperatures and pressures).
  • Using observations to improve the simulation of air quality at various spatial and temporal scales.
  • Understanding interactions of meteorology and air quality.
  • Improving the theoretical understanding of chemical processes in the air and near the ground.
  • Understanding the implications of changes in emissions on air quality, water quality, and human health.

Graduate theses

Graduate students often use CMAQ in their master’s and doctoral work, which sometimes results in peer-reviewed publications:

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Private sector

Several private companies utilize CMAQ when serving their clients, with the main focus on environmental, air quality, and meteorological support and consulting. Some of those companies maintain tailored and proprietary versions of the CMAQ software.

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CMAQ impact: domestic and international

The map below illustrates the global nature of the CMAQ community and the large number of model downloads that have occurred over the last decade.

Map showing number of CMAQ downloads by country with the US and China having the most downloads (12058 and 10013 respectively)

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