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 PM2.5 emission size distribution to improve aerosol size distribution simulation. Included gravitational settling for coarse aerosols.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.