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CMAQ 4.7.1 Release Notes

The Model Development Team is pleased to announce that CMAQ version 4.7.1 has been delivered to CMAS for public release. You can access the model from the CMAS. Exit EPA Disclaimer.

The changes and new features of this release are:

  1. Aqueous chemistry
    1. Mass conservation improvements
      1. Imposed 1 second minimum timestep for remainder of the cloud lifetime
        after 100 "iterations" in the solver
      2. Force mass balance for the last timestep in the cloud by limiting
        oxidized amount to mass available
    2. Implemented steady state assumption for OH
    3. Only allow sulfur oxidation to control the aqueous chemistry solver
      timestep (previously, reactions of OH, GLY, MGLY, and Hg for
      multipollutant model also controlled the timestep)
  2. Vertical Advection
    1. Added additional divergence-based constraint on advection timestep
    2. Vertical advection now represented with PPM to limit numerical diffusion
  3. Multipollutant model updates
    1. Bug fix to facilitate in-line emissions option
    2. Mercury
      1. Dicarboxylic acid reduction mechanism applied to aqueous phase
        oxidized mercury species
      2. Cl oxidation pathway based on Donohoue et al 2005 J. Phys. Chem. A 109(34)
    3. Lowered CB05 mechanism unit yields for acrolein from 1,3-Butadiene
      tracer reactions to be consistent with laboratory measurements
  4. Photolysis
    1. JPROC/phot_table and phot_sat options
      1. Expanded lookup tables to facilitate applications across the globe and
        extended vertical extent to 20km
      2. Updated temperature adjustments for absorption cross sections and
        quantum yields
      3. Revised algorithm that processes TOMS datasets for OMI data format
    2. In-line option
      1. Asymmetry factor calculation updated using values from Mie theory
        integrated over log normal particle distribution; added special
        treatment for large particles in asymmetry factor algorithm to avoid
        numerical instabilities
  5. Instrumented Models
    1. DDM-3D
    2. Sulfur Tracking
    3. Primary Carbon Apportionment

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Known Issues:

1) When using the inline option for biogenic emissions, only one hour output
timesteps are supported

2) DDM-3D is currently only operational with the "eddy" vertical diffusion module
(DDM for the acm2 or acm2_inline modules will be available in the next release)

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