1.5. New Features in Version 4.6
CMAQ version 4.6 contains several new features and improvements from the previous release of the model. An important global
update that affects ICON, BCON, and CCTM is the new dynamic layer configuration. Similar to the horizontal grid configuration
that is defined at execution using a grid description file, the vertical layer configuration is now defined using a run-time
environment variable that points to a 3-d input meteorology file that contains the applicable vertical structure. It is no
longer necessary to recompile these programs when the vertical layer structure changes.
Additional, process-specific features are listed below.
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Aerosols
- Updated ISORROPIA to v1.7 (includes correction in activity coefficients for temperatures other than 298 K
- Revised to use T, RH-dependent “gamma” (heterogeneous N2O5 reaction probability) from Evans & Jacob (2005)
- Upper limit set for the relative humidity input to ISORROPIA (95%)
- Updated parameters written to the aerosol diagnostic file
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Chemistry
- 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)
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PBL modeling
- New ACM2: combined non-local and local closure scheme
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Plume-in-Grid
- Capability for AE4 mechanisms
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Mercury
- Capability for CB05, AE4 mechanism
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Hazardous Air Pollutants
- 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)
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Carbon Apportionment
- Added capability for CB05 mechanism
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Sulfate Tracking
- Added capability for : CB05, AE4 mechanisms ; and “cloud_acm” module
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CGRID restart file
- 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)
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Parallel I/O library
- Various updates (new version required for CMAQv4.6 compilation)
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Other
- Added a utility program to convert MCIP data into HYSPLIT format
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Meteorology (MCIPv3.2)
- Modified I/O API header variable settings for WRF-ARW (WRF-EM) to reflect additional capability to have center of coarse domain
located elsewhere than the center of the projection. (Note that applications of CMAQ with WRF-ARW input will no longer adhere
to the “grid family” paradigm for the Models-3 I/O API, and a separate GRIDDESC file will be required for each grid.)
- For non-PX runs only: Corrected error in bookkeeping “last wet time” in M3Dry dry deposition when Pleim-Xiu land-surface model is not run. Also now use ground temperature rather than 2-m air
temperature to calculate ground-level relative humidity. Allow canopy to dry out gradually between 2 and 3 hours after “last wet time”.
- Corrected checking and setting I/O API header variables for Mercator and polar stereographic projections.
- Added restriction that Eta/Ferrier microphysics scheme in WRF-ARW (WRF-EM) is currently incompatible with CMAQ.
- Added capability to fill land-use lookup table fields in MM5v3-formatted data that have been converted from MM5v2 format.
- Corrected filling of vertical velocity array for MM5v2-formatted data.
- Added land-water mask to output in GRIDCRO2D.
- Corrected logic for processing MM5's TERRAIN file to account for expanded grid in coarse domain.
- Updated condition for GRIDCRO3D output to reflect new WRF-ARW (WRF-EM) vertical coordinate descriptor in I/O API.
- Optimized calculations of species-specific dry deposition constants.
- Use land-water mask rather than dominant land use array to determine water points.
- General code clean-up (removed unused variables, moved variables from global to local within subroutines, eliminated type
mismatches, corrected/clarified comments).
- Added ASCII file that includes calling tree for MCIP.
- Updated frequently asked questions list.
- Updated version stamp.