CMAQ

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 CMAQv5.2 System Updates Incorporated updates to representation of organic nitrate lifetimes and halogen chemistry for better representation of tropospheric chemistry on hemispheric scales. Added new sources of secondary organic aerosols (heterogeneous uptake of glyoxal and methylglyoxal in CB6) and updated properties of traditional secondary organic aerosol. The volatility of both secondary and primary organic compounds are now treated consistently with each other. Incorporated updated instrumented models: DDM-3D, Sulfur Tacking, Integrated Source Apportionment (ISAM) consistent with science process updates. New Features and Processes in v5.2 Incorporated the CB6 chemical mechanism to incorporate new information on gas-phase kinetics. Incorporated representation of stratosphere-troposphere exchange process on three-dimensional O3 distributions, using a space and time varying potential vorticity scaling approach. Incorporated a new physics based windblown dust emission model that yields better agreement with observations of fine and coarse PM and constituents. Added a new model species to account for the organic aerosol compounds resulting from combustion processes.For up-to-date documentation, source code, and sample run scripts, please clone or download the CMAQ git repository available through GitHub: https://github.com/USEPA/CMAQ/tree/5.