CMAQv5.1

The Community Multiscale Air Quality (CMAQ) model is an active open-source development project of the U.S. EPA that consists of a suite of programs for conducting air quality model simulations. CMAQ combines current knowledge in atmospheric science and air quality modeling, multi-processor computing techniques, and an open-source framework to deliver fast, technically sound estimates of ozone, particulates, toxics and acid deposition.

For further information please visit the EPA website for the CMAQ system: www.epa.gov/cmaq

CMAQv5.1 System Updates

• Improved consistency in representation of radiation attenuation by clouds between WRF and photolysis module in CMAQ.
• Included the Rodas3 Rosenbrock solver to solve cloud chemistry, kinetic mass transfer, ionic dissociation, and wet deposition.
• Improvements to the land-surface model and ACM mixing scheme to enable finer-scale applications.
• Improvements in representation of aerosol mixing state and optical properties for 2-way coupled WRF-CMAQ configurations.

New Features and Processes in v5.1

• Incorporated the RACM2 chemical mechanism.
• Included detailed representation of impacts of halogen chemistry on O₃ in marine environments. Improved representation of O₃ in coastal regions as well as representation of O₃ loss in air masses transported intercontinentally across vast oceans.
• New secondary organic aerosol (SOA) sources from isoprene, alkanes, and polyaromatic hydrocarbons (PAHs).
• Incorporation of new binary nucleation and updates to PM_2.5 emission size distribution to improve aerosol size distribution simulation.
• Included gravitational settling for coarse aerosols.