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CMAQ

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Code for U.S. EPAs Community Multiscale Air Quality Model (CMAQ) for estimating ozone, particulates, toxics, and deposition of acids and nutrients at neighborhood to global scales.

github.com/USEPA/CMAQ ↗

CMAQ went global in v5.5, and has been patching that surface ever since.

air-qualityatmospheric-modelingepascientific-computingsource-apportionment
◆Current state
CMAQ is the EPA's Community Multiscale Air Quality modeling system, used for regulatory and research air quality simulation. Its release rhythm is strictly two-tier: numbered major versions carry new science and fresh benchmark datasets, while the x.y.z.n updates carry bug fixes against documentation and benchmarks that stay pinned to the parent version. The current line is v5.5, which introduced CRACMM2 chemistry and coupling to MPAS-A meteorology, followed by three patch rollups.
◆Where it's heading
The v5.5 patches cluster around the newest and most sensitive components. ISAM source apportionment and DDM-3D sensitivity analysis account for corrections in every one of the three updates, and CRACMM2 needed fixes within months of release. That is the expected shape after a major version lands: the science is stable, the instrumentation built on top of it is not. Parallel I/O work in the latest patch suggests the global configurations are now being run at scales that expose throughput limits.
◆Prediction
The next major version will fold these fixes in with new science, documentation and benchmark data — the release notes state this explicitly each time. Until then, expect further ISAM and DDM-3D corrections, which have appeared in every patch so far.

◆Recent moves

  1. 1y ago

    CMAQ 5.5.0.3 enables parallel I/O, fixes DDM-3D control files

    The third v5.5 patch rollup, notable for parallel I/O work alongside a larger DDM-3D control file string limit and a stray merge conflict cleanup. Documentation and benchmarks stay on v5.5, so this is for users who want the fixes ahead of the next major release.

    View source ↗
  2. 1y ago

    CMAQ 5.5.0.2 corrects ISAM aerosol and cloud processing

    The heaviest of the v5.5 patches: ISAM aerosol and cloud processing corrections, pcVOC and NOy added to ISAM species lists, a denominator conversion factor fix, and a DDM3D correction to the EBI solvers. Source apportionment results from earlier v5.5 runs may shift as a result.

    View source ↗
  3. 1y ago

    CMAQ 5.5.0.1 fixes SAPRC mechanism runs and NLCD mapping

    The first v5.5 patch addresses a bug that prevented CMAQ running with SAPRC mechanisms at all, plus a corrected NLCD to BELD3 land-cover mapping for shrub and scrub classes and CRACMM2 fixes for ISAM. A blocking bug in a chemical mechanism reaching release says the v5.5 test matrix did not cover every mechanism path.

    View source ↗
  4. 1y ago

    CMAQ 5.5 adds global simulation coupled to MPAS-A

    ⚡ SPARK

    The major release the current line is built on: CRACMM2 chemistry with reworked formaldehyde reactions affecting ozone and secondary organic aerosol, and support for pre-configured global simulations driven by MPAS-A meteorology. Every patch since has been fixing instrumentation around this science.

    View source ↗
  5. 1y ago

    CMAQ 5.4.0.5: minor ELMO output fixes

    A single-PR patch touching ELMO output algorithms, and the final update to the v5.4 line before v5.5 arrived a month later. Housekeeping on a version already superseded.

    View source ↗
  6. 2y ago

    CMAQ 5.4.0.4 fixes RBSTATS under ROS3, corrects a molecular weight

    A v5.4 patch rollup covering RBSTATS behavior with the ROS3 solver, a molecular weight correction, config updates and emissions tutorial revisions. A wrong molecular weight is the kind of quiet error that propagates through every mass calculation downstream of it.

    View source ↗