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Community Multiscale Air Quality (CMAQ)
Research Programs
Description of Model Changes for the 2003 Release of the CMAQ Model
1. Introduction
The Community Multiscale Air Quality Model (CMAQ) has been extensively revised in 2003. Changes include: updated science, corrected implementations, efficiency enhancements, and bug fixes. There is a preliminary evaluation of the new release of the CMAQ model on the EPA Models-3 website comparing model results to observations of gas and aerosol species. There are also model-to-model comparisons between the 2003 release and the 2002 release. The biggest changes involve aerosol modeling, particularly nitrate aerosols and secondary organic aerosols (SOA). Nitrate modeling was updated so it is consistent with the most recent literature and the SOA implementation was corrected to allow for reversible semi-volatility. These changes resulted in substantially lower concentrations of both aerosol nitrates and SOA. Minor changes have also been made to aqueous processes and dry deposition. The details of changes to chemistry/transport modeling are presented in Section 2.
Air Toxics
CMAQ ModelScience Documentation
Release Notes v4.6
Release Notes v4.5
Release Notes v4.4
Release Notes v4.3
- Carbon Bond (CB05) mechanism and associated EBI solver
- Include the gas-phase reactions involving N2O5 and H2O
- Removed obsolete mechanism combinations (e.g. gas+aerosols w/o aqueous)
- New ACM2: combined non-local and local closure scheme
- Capability for AE4 mechanisms
- Capability for CB05, AE4 mechanism
- Increased number of gas-phase HAPs; added several toxic metals and diesel components in particulate material (adapted for CB05 and SAPRC99 chemical mechanisms, and AE4)
- Added capability for the CB05 mechanism
- Added capability for: CB05, AE4 mechanisms; and "cloud_acm" module
- Added a CGRID restart file (used to initialize next day's simulation; permits flexibility in the “CONC” file; can write subset of species and layers for the CONC file)
- Various updates (new version required for CMAQv4.6 compilation)
- Added a utility program to convert MCIP data into HYSPLIT format