CMAQ v5.5 Release (October 2024)

CMAS Center Announcements
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Announcing the release of CMAQ version 5.5 (October 2, 2024)

CMAQ URL: www.epa.gov/cmaq

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The U.S. EPA Office of Research and Development and the Community Modeling and Analysis System Center are pleased to announce the release of CMAQ version 5.5.

What’s new in CMAQv5.5?

  • Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM) version 2 including updated formaldehyde chemistry impacting ozone and secondary organic aerosol formation

  • New support for running pre-configured global CMAQ simulations coupled with meteorology from the Model for Prediction Across Scales – Atmosphere (MPAS-A)

  • Expanded capabilities of the Integrated Source Apportionment Method (ISAM) to quantify source contributions to total secondary organic aerosol (SOA) and individual species

  • Updates to ISAM source attribution estimates, mainly impacting coarse particles and secondary organic aerosols formed through cloud processes

  • Updates to the Decoupled Direct Method (DDM) to improve second order ozone sensitivities

  • Updated chemistry to properly capture photolysis effects from sub-grid clouds

  • Revised algorithms for modeling dry deposition (M3DRY and STAGE updates)

  • Improved accuracy and error checking for BDSNP soil NO in the MEGAN biogenic emissions algorithm

  • MCIP (meteorology preprocessor) updates to grid origin definition for fine scale Lambert Conformal Grids (i.e., < 4km )

  • Updates to Sulfur Tracking Model (STM) to properly attribute sulfate from gas phase chemistry

  • Updates to the Explicit and Lumped Model Output (ELMO) synthesizer to fix erroneous output for several PM aggregates including PMF_OC, PMF_NCOM, TNO3

  • New shp2cmaq python tool to convert GIS shapefiles into gridded netCDF mask files that can be used for defining regions and region families with DESID and using geographic source regions when running CMAQ-ISAM

  • Simplified workflows for easier CMAQ installation

See the full list of CMAQv5.5 updates on our new CMAQ Wiki page: CMAQv5.5 Series FAQ · USEPA/CMAQ Wiki · GitHub

Download the source code and scripts, and access all documentation for this release from the USEPA GitHub repository: GitHub - USEPA/CMAQ: Code for U.S. EPA’s Community Multiscale Air Quality Model (CMAQ) which helps in conducting air quality model simulations

Two-day test data for CMAQ version 5.5 are available from the CMAS Data Warehouse: Test Cases | US EPA

Documentation for this release includes the following:

  • Frequently asked questions for upgrading to version 5.5

  • New and updated step-by-step tutorials for different features and functions of the software including tutorials for running CMAQ using chemical mechanism CRACMM2

  • Release notes providing details on major changes and new features

  • Tables of model species and chemical reactions in each chemical mechanism available in v5.5

CMAQ version 5.5 documentation direct link on GitHub: CMAQ/DOCS/README.md at main · USEPA/CMAQ · GitHub

Please report any bugs or problems with this release to the CMAS User Forum: https://forum.cmascenter.org

Additional user support, including training courses and other CMAS-supported software products is available through the CMAS Center website: www.cmascenter.org

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