CMAQv5.5 Series FAQ

Frequently Asked Questions for Upgrading to the Latest CMAQ Version

Table of Contents:

• Do I need to update from v5.4 to v5.5?
• What do I need to do to update from v5.4 to v5.5?
  • What differences should I expect in the required model input files?
  • What differences should I expect in my model output files?
• What differences should I expect in my model results with v5.5 compared to v5.4?
• Additional FAQ
• Technical support for CMAQ

Do I need to update from v5.4 to v5.5?

CMAQv5.5 includes many scientific enhancements and new features that will benefit certain applications. See the v5.5 Release Notes for a description of each change.

Instrumented Models

• Several updates were incorporated in CMAQ-ISAM: (1) accounting for the loss of aerosol mass from gravitational settling was incorporated, so that the tagged and bulk concentrations matched more precisely; (2) a new tag was incorporated to attribute O3 to be of “stratospheric origin” based on the PV-scaling methodology; (3) addressed instabilities associated with mass distribution between tags immediately after cloud chemistry. See: CMAQ-ISAM Release Notes for more information.

• In CMAQ-DDM: (1) enabled estimation of sensitivity of O3 to PV-O3 specification; (2) corrected calculation of second-order sensitivity in chemistry routines; (3) corrected error that caused incorrect dry deposition sensitivity in output. See CMAQ-DDM Release Notes for more information.

On-line coupling of CMAQ with meteorological models

• A bug was identified within the CMAQ to WRF coupling routine in the CMAQv5.4 series; layer heights were incorrectly being assigned to wind speed in the plume rise calculations leading to erroneous allocation of point source emissions. Users of WRF-CMAQ are strongly encouraged to update to CMAQv5.4. See the WRF-CMAQ Release Notes for more information.

• CMAQv5.5 is the first public release that allows coupling of CMAQ with the Model for Prediction Across Scales (MPAS).

Chemistry

• In CRACMM1, the rate of sulfate catalyzed IEPOX was updated. The impact is to increase sulfate (as less sulfate is taken up as organosulfate) and to decrease organic aerosol.

• CMAQv5.5 introduces version 2 of the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM2). CRACMM2 includes several updates to CRACMM1. Many updates are intended to improve the representation of secondary formaldehyde (HCHO) in CRACMM. These include the incorporation of the AMORE v1.2 isoprene condensation into the primary CRACMM mechanism, updates to HCHO yields from monoterpenes, and the addition of styrene as a new explicit species. Additional updates include changes to monoterpene nitrates that affect SOA formation and NOx recycling, the inclusion of emitted methane (ECH4), heterogeneous uptake of HO2 and NO3 radicals, and changes in how emissions of certain aromatic species are mapped to CRACMM species.

• The photolysis module was updated to correct an error in calculation of cloud optical depth for grid cells with sub-grid/convective clouds. The net impact is to increase the attenuation of photolysis frequencies under cloudy conditions.

Dry Deposition/Air Surface Exchange

Stratosphere-Troposphere Exchange

• Removed dependency on sigma-P coordinate system in PV-O3 scaling. The update impacted O3 distributions between 300-100hPa and generally improved model estimates relative to observations at these levels.

Emissions

Process Analysis & Sulfur Tracking Model (STM)

• Fixes to Sulfur Tracking Model (STM) correct errors in attribution of sulfate from gas phase chemistry, which inadvertently got introduced in the previous model version. See CMAQ-STM Release Notes for more information.

Structural Improvements

• Updated model code and run-scripts so that PV-O3 scaling can be invoked now as a runtime option.

Diagnostic Options

• Updates to ELMO to fix erroneous output for various PM aggregates (PMF_OC, PMF_NCOM, TNO3, etc.)

Pre-processors and Utilities

• MCIP: Updates were implemented to the definition of grid origin for fine-scale lambert conformal grids (i.e. < 4km resolution)

Post-processors

• Corrected deposition SpecDef for NOy species.

• Improved checks on formulas used by Combine.

• Increase character limit for station ID in sitecmp_dailyO3 to accommodate emerging networks.

Python Tools

• New Python tool to create CMAQ-ready grid masks from a shape file for defining regions and region families with DESID and using geographic source regions when running CMAQ-ISAM

What do I need to do to update from v5.4 to v5.5?

What differences should I expect in the required model input files?

• If you have already successfully migrated to v5.4, you will not need to any additional input to run with the analogous options in v5.5. However, if you trying to run with the newest released version of CRACMM in v5.5, users will have to generate or map existing emissions to CRACMMv2.0. For additional information on generating emissions for CRACMMv2.0 please see the CRACMM GitHub Page.

What differences should I expect in my model output files?

• The photolysis diagnostic files were updated to include additional variables (e.g., absorption AOD) that may help in evaluation of optical properties against measurements.

What differences should I expect in my model results with v5.5 compared to v5.4?

Natural Emissions

• Emissions from natural sources (e.g., lightning, wind-blown dust, biogenic emissions) remained the same in v5.5 when compared to v5.4.

Ozone

• Summary:

PM2.5

• Summary:

Deposition

• Summary:

Additional FAQ

A more general list of Frequent CMAQ Questions can be found on our website: https://www.epa.gov/cmaq/frequent-cmaq-questions

Technical support for CMAQ

Technical support for CMAQ, including questions about model inputs, downloading, compiling, and running the model, and pre- and post-processing utilities, should be directed to the CMAS Center User Forum. Please read and follow these steps prior to submitting new questions to the User Forum.