[ Home | Homework | ]


  1. *CMAQ is an acronym for the Community Multi-scale Air Quality Model, a sophisticated atmospheric dispersion model developed by the US EPA to address regional air pollution problems.*
  2. CMAQ is a first-principles scientific computer model that comprehensively represents the most important processes affecting air quality and atmospheric chemistry. Emissions from a wide range of sources are included, as well as transport by winds and deposition due to precipitation events. CMAQ uses an extensive database of atmospheric chemical reactions to predict the chemical production and loss of hundreds of pollutants as they are carried downwind from their sources. In addition to gas-phase species, many pollutants exist partially or wholly in airborne particles, giving them the potential to interact with incoming solar radiation and clouds in complicated ways.
  3. CMAQ brings together three kinds of models:
    - Meteorological models to represent atmospheric and weather activities.
    - Emission models to represent man-made and naturally-occurring contributions to the atmosphere.
    - An air chemistry-transport model to predict the atmospheric fate of air pollutants under varying conditions.
  4. *For example:
    - Ozone forms in the atmosphere when nitrogen oxides interact with volatile organic compounds in the presence of sunlight. Ozone is called a "secondary pollutant" because it is often not emitted directly, but is created in the atmosphere by reaction from other "primary" pollutants that were emitted from cars, factories, crops, forests, etc.
    - Ammonium sulfate is formed in fine particulate matter when sulfuric acid (formed largely in cloud water) interacts with gas-phase ammonia.
  5. *Meteorological conditions such as subsidence inversions found in high-pressure regions decrease the amount of fresh air available for dilution of air emissions, and increase the rate of production of secondary air pollutants.
  6. .

Used For 

* from Wikipedia

Intro Lectures

Ozone (O3) in Greater Vancouver

Ozone Chemistry (simplified example using carbon monoxide CO)
  • Focus on section 8.2 Tropospheric Ozone of free online Atmospheric Chemistry textbook, or get the whole book:  "Atmospheric Chemistry" by István Lagzi, Róbert Mészáros, Györgyi Gelybó, Ádám Leelőssy
    "Copyright © 2013 Eötvös Loránd University, Budapest, Hungary.
    This book is freely available for research and educational purposes." 
  • Note: Our HW-cmaq1 is based on this CO example, but using eqs from cmaq cb6.
  • Also see summary of key chemicals, from Seinfeld & Pandis, 2006: "Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, 2nd Ed.", ISBN: 978-0-471-72018-8 . Wiley.  1232 pages.

Chemistry: Carbon-bond Mechanism v6 (CB6)

  1. List of CB6 chemical reactions and rate constants (Yarwood, 2010; extracted from the full report, see next link)
  2. CB6 Final Report (Yarwood et al, 2010).
  3. Slides from a presentation of CB6 carbon bond mechanisms by Yarwood et al 2010.

Chemistry: Carbon-bond Mechanism v7 (CB7) - proposed in 2021

  1. Yarwood, Shi, Beardsley, 2021: Develop CB7 Chemical Mechanism for CAMx Ozone Modeling. 
  2. xx 


smog over bc.
Satellite photo of smog over most of BC on 31 July 2018.  Both photochemical smog and forest-fire smoke.  Stratus clouds & fog along the west coast.

CMAQ Model


Version 5.3.3 (2021)

  1. Main CMAQ home page: 

Version 5.3.1 (Dec 2019)

  1. Summary of CMAQ update 5.3.1.  Appel et al, 2020: The Community Multiscale Air Quality (CMAQ) Model Versions 5.3 and 5.3.1: System Updates and Evaluation.  Geoscience Model Development. . 
  2. Sixth CMAQ Peer Review Report, 2019.   Barsanti et al, 2019: The Sixth External Peer Review of the Community Multiscale Air Quality (CMAQ) Modeling System. 

Model Dynamics, Physics & Parameterizations

  1. Extremely complex.  For a simple overview, see .
  2. For details, see slightly outdated version at: .
  3. For operational guidance details, see:
  4. Other documentation is at: .
Advection Schemes
  1. Stull's brief review of numerical methods for advection in regular grids.
    See accompanying animations (zipped) created by Pedro Odon for
    1. Forward in time, Centered in Space (FTCS)
    2. Forward in time, Backward in Space (FTBS)
    3. Centered in time, Centered in Space (CTCS)
    4. (skipped)
    5. Runge-Kutta 3rd order in Time, Centered in Space (RK3CS)
  2. CMAQ Chapter 7 on Advection.
  3. Colella, P., & Woodward, P.R. (1984). The Piecewise Parabolic Method (PPM) for gas-dynamical simulations, J. Comp. Phys., 54, 174–201. doi: 10.1016/0021-9991(84)90143-8 .
  4. Current version of fortran code for PPM horizontal 1-D advection: and get the latest version.  As of this writing it was for version 5.2.1 (March 2018).
    Then look in this path to get the hppm.F subroutine:   CCTM/src/hadv/yamo/hppm.F
Code sources
  1. To view NetCDF and other types of input and output files, use the Panoply program:
    a. download to your computer the Java 8 code (Mac users need to run Safari, and set Safari preferences Web to allow the NASA site to use the Java plug-in), then
    b. download the Panoply program from NASA.

  2. CMAQ Source Code.  


CMAQ installation tips in 2021 by our TA, Tim Chui.

More Info: 

[ Home | Homework | ]
Copyright © 2018, 2021 by Roland Stull.