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CMAQ belongs to the Eulerian class of mathematical models, tracking the movement of pollution plumes over time on a fixed three-dimensional grid. CMAQ simulates hourly concentration and deposition for a large number of chemical species for multiple vertical layers, from the earth's surface (the air we breathe) up to the tropopause where pollutants are transported across the globe. CMAQ output represents volume-average pollutant concentrations for every grid cell and vertical layer in the model domain.
A year-long simulation of CMAQ over the U.S. can produce up to 45 terabytes of data. Because CMAQ input and output data are so large they are stored as binary files using Network Common Data Form (netCDF). CMAQ data can be visualized using various tools (e.g., VERDI, Paraview, Vapor, R, Matlab, etc.). The data can also be summarized spatially to represent values for a census tract or watershed or it can be extracted for a specific location. Results from some of EPA's modeling efforts are provided for download and visualization.
What does CMAQ output look like? This interactive map tool can be used to view hourly surface-level estimates over the U.S. for ozone or PM2.5 for any month in 2012. Model-estimated wind speed and direction are also included to show how the model simulates the movement of air pollution from the pollution sources to downwind locations. This website can be used to explore how ozone and PM2.5 levels change throughout the day, for example morning versus afternoon levels, and throughout different seasons.
EPA’s Air QUAlity TimE Series Project (EQUATES) uses the state-of-the-science emissions, meteorological, and air quality methods and models to provide a unified set of modeling data for 2002-2017 to support regulatory and policy analyses as well as health and ecological studies.
EQUATES meteorology, emissions, and air quality modeling datasets have been packaged to meet various collaborator needs and are available to download. CMAQ input files for domains covering the contiguous U.S. are available for use in new modeling simulations. CMAQ output data is available for criteria pollutants, nitrogen and sulfur deposition, as well as other chemical species often used in health and ecological studies.
Click on the link below to learn more about EQUATES or fill out the form at the bottom of the page to download an EQUATES dataset.
CMAQ input and output files are hosted on the CMAS Data Warehouse Google Drive and EPA's Remote Sensing Information Gateway (RSIG). In order to help us prioritize what datasets are shared on this platform, please let us know how you intend to use the downloaded data.
After submitting the form, you will be redirected to the download page. You can opt-out of the survey by submitting a blank form.