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Data System Name: Community Multi-scale Air Quality Model (CMAQ)
Data System URL:
Contact Person: Norm Possiel
Contact e-mail: none


About the Data System (Purposes, Audience)

The CMAQ model is a comprehensive, three-dimensional, grid-based Eulerian air quality model designed to estimate ozone and particulate concentrations and deposition over a broad range of temporal and spatial scales. CMAQ, which is a publically available, peer-reviewed, state-of-the-science model, consists of a number of science attributes that are critical for simulating the oxidant precursors and non-linear organic and inorganic chemical relationships associated with the formation of ozone and sulfate, nitrate, and organic aerosols. CMAQ also simulates the transport and removal of directly emitted particles which are speciated as elemental carbon, crustal material, nitrate, sulfate, and organic aerosols. Additionally, the multi-pollutant version of CMAQ simulates mercury and over 30 toxic volatile organic compounds and metals.

CMAQ is being used by the US EPA, State and Regional environmental organizations, universities, and independent research organizations to provide data in support of a wide range of analyses linked to understanding the spatial and temporal patterns of pollutant concentrations and deposition in relation to emissions and meteorology and as part of regulatory programs for evaluating the effectiveness of emissions control strategies for attainment of National Ambient Air Quality Standards. The US EPA’s Office of Air Quality Planning and Standards in collaboration with the Office of Research and Development have recently run CMAQ for the full year of 2002 using a 2002-based air quality modeling platform.


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CMAQ is a product of the US EPA’s Office of Research and Development and is updated on a regular basis to reflect the current state-of-the-science in atmospheric chemistry and meteorological processes.



List of Publications, Papers, Presentations

Papers and reports on the development and application of CMAQ by various groups in the modeling community can be found at the following URL:

Data System Scope

Data Content

Datasets Served

The CMAQ modeling system contains both input and output datasets which include: meteorological and emissions inputs, and concentration and deposition outputs. US EPA has performed CMAQ simulations for the full year of 2002 for two modeling domains which together cover the Eastern and Western US along with adjacent portions of Canada and Mexico. This dataset includes the types of parameters listed below at a horizontal resolution of approximately 12 x 12 km and 14 layers in the vertical up to 100mb.


Meteorological input files for CMAQ contain hourly, gridded data for more than 50 meteorological parameters. Emissions input files for criteria pollutant (e.g., ozone and PM) modeling contain hourly, gridded data for 30 gas and particle pollutant species. The CMAQ output files contain hourly, gridded concentrations for 30 gas and particle species and wet and dry deposition for 18 species. The emissions and meteorological input and CMAQ concentration output files contain data for all vertical layers specified for the particular model simulation.

Spatial - Temporal Coverage

The spatial and temporal coverage of CMAQ applications is user-defined. CMAQ applications by the US EPA typically cover national spatial scales at 36 x 36 km and regional scales at 12 x 12 km resolution. Temporal scales range from episodic to annual. The US EPA 2002 CMAQ dataset is based on modeling at 12 x 12 km resolution for the full year of 2002.



The outputs of CMAQ for baseline and emissions control cases are post-processed to create spatial fields of ozone and PM2.5 concentrations in a format for input to health-benefits calculation models. In addition, ozone and PM2.5 from CMAQ are blended with ambient data through the application of various “data fusion” techniques to provide concentration fields for analysis with health effects data.

Forecasting and Reanalysis

The US EPA and other organizations run CMAQ in near “real-time” to provide daily forecasts of air quality based on model predictions of ozone and PM2.5

Model/Emissions Evaluation

The US EPA conducts operational, diagnostic, and dynamic evaluations of CMAQ predictions using ambient data from various monitoring networks including AQS, CASTNET, NADP, SEARCH, and special field studies having measurements at ground level and aloft.

Characterization, Trends, Accountability

The predictions from CMAQ simulations for multiple years provide a means to complement air quality measurements for characterizing trends and for evaluating the effectiveness of control programs as part of “accountability” analyses and dynamic evaluation of the model. The US EPA is building a dataset of annual CMAQ predictions which began with model simulations for 2002.


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Data System IT

Primary/Official Store for Some data

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Data Consolidation/integration

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Providing Data Access to users/externals

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Data Processing

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Decision Support (e.g. some integration into user business process)

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End-to-End Integration

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Other DS Values

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Data Access and/or Output Interoperability

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Reusable Tools and Methods

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Security Barriers and Solutions

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User Feedback Approach

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Other Architecture

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User Provided Content