Global Environmental Multiscale model‒Modelling Atmospheric CHemistry (GEM-MACH) version 3.1.0.0

This record contains source code and accompanying documentation for version 3.1.0.0 of the Global Environmental Multiscale model‒Modelling Atmospheric CHemistry (GEM-MACH) online chemical weather forecast model developed by Environment and Climate Change Canada (ECCC).  GEM-MACH 3.1.0.0 has been described by Moran et al. (2025).  This model was used by version 023 of the Regional Air Quality Deterministic Prediction System (RAQDPS023) of ECCC to make operational, 72-hour air quality forecasts twice daily from December 2021 until June 2024 on a latitude-longitude regional grid covering much of North America from northern Mexico in the south to the Canadian Arctic archipelago and Alaska in the north.  Horizontal grid spacing of 10 km was used together with 84 hybrid vertical levels stretching from the Earth’s surface to 0.1 hPa.

GEM-MACH version 3.1.0.0 is composed of two primary parts, version 5.1.0 of the ECCC Global Environmental Multiscale (GEM) numerical weather prediction model and version 3.1.0.0 of the MACH atmospheric chemistry library.  The executable for GEM-MACH is obtained by providing the MACH chemistry library to GEM when generating its executable.  GEM-MACH is thus an extension of the standard GEM model.

Version 5.1 of the GEM code is free software which can be redistributed and/or modified under the terms of version 2.1 of the GNU Lesser General Public License as published by the Free Software Foundation.  The GEM source code has been developed by the Meteorological Research Division of ECCC.  This code is available for download from https://github.com/ECCC-ASTD-MRD/gem/tree/5.1-branch.

Version 3.1.0.0 of the MACH atmospheric chemistry library is free software which can be redistributed and/or modified under the terms of the GNU Lesser General Public License as published by the Free Software Foundation – either version 2.1 of the license or any later version.  The MACH source code has been developed by the Air Quality Research Division of ECCC.  This code is provided below in the file named “MACH_v3.1.0.0_source_code.zip” along with two files (“gem_settings_nml.pdf” and “outcfg_out.pdf”) containing listings of two important input files that are used to configure GEM-MACH3.1.0.0 for the RAQDPS023 application. 

File “MACH_v3.1.0.0_source_code.zip”  ‒  Contains chemistry library source code for MACH3.1.0.0

File “gem_settings_nml.pdf”  ‒  File containing list of user-defined settings in Fortran namelist format for various dynamical, physical, and chemical options used by the RAQDPS023

File “outcfg_out.pdf”  ‒  File containing list of user-defined choices for output fields used by the RAQDPS023

A number of GEM-MACH3.1.0.0-related documentation files have also been included below: 

File “GEM-MACH3.1.0.0_README_overview.pdf”  ‒  Webpage listing providing overview of RAQDPS023 delivery based on GEM-MACH 3.1.0.0.

File “GEM-MACH3.1.0.0_README_variables.pdf”  ‒  Tables providing names and definitions of GEM-MACH 3.1.0.0 output variables.

File “GEM5.1_gem_settings_nml_description.pdf”  ‒  Webpage listing that describes setting options available in “gem_settings.nml” file input by GEM-MACH to specify GEM dynamical, physical, and numerical configuration.

File “GEM-MACH3.1.0.0_chemistry_cfgs_description.pdf”  ‒  Webpage listing that describes setting options available in “gem_settings.nml” file input by GEM-MACH to specify MACH chemistry configuration.

File “GEM5.1_outcfg_out_description.pdf”  ‒  Webpage listing that describes format of “outcfg.out” file used to specify GEM and MACH output fields.

File “G-M3.1.0.0-rc7_tree_diagram_starting_from CHM_exe2.png”  ‒  Image of Doxygen-generated subroutine tree starting from subroutine “CHM_exe.ftn90”.

File “G-M3.1.0.0-rc7_tree_diagram_starting_from MACH_PM_CHEM.png”  ‒  Image of Doxygen-generated subroutine tree starting from subroutine “MACH_PM_CHEM.ftn90”.

In addition, some reports and presentations that are cited by Moran et al. (2025) but that are difficult to find online are included here:

File “KaramchandaniEA_1985_ERT_vol8.pdf”  ‒  Copy of report

Karamchandani, P., Lurmann, F., and Venkatram, A.: ADOM/TADAP Model Development Program: Volume 8.  Central Operator, ERT Document P-B980-535, May, Environmental Research & Technology, Inc., Newbury Park, California, 136 pp., 1985.

File “MoranEA_1999_AURAMS_Conceptual_Design.pdf”  ‒  Copy of report

Moran, M. D., Bouchet, V., Dastoor, A., Gong, S., Gong, W., and Makar, P. A.: Conceptual design for the AES regional particulate-matter model/unified air quality model, Atmospheric Environment Service, Toronto, Ontario, October, 102 pp., 1998.

File “Stockwell+Lurmann_1989.pdf”  ‒  Copy of report

Stockwell, W. R. and Lurmann, F. W.: Intercomparison of the ADOM and RADM gas-phase chemical mechanisms, Report prepared for the Electric Power Research Institute, Palo Alto, California, 266 pp., 1989.

File “StroudEA_2010.pdf”  ‒  Copy of presentation

Stroud, C., Moran, M., Makar, P., Gong, W., Gong, S., Morneau, G., Bouchet, V., Dann, T., Wang, D., and Huang, L.: Impact of updates to BEIS v3 boreal forest emissions on Canadian air quality forecasts, Nov. 16-18, 2nd International Workshop on Air Quality Forecasting Research, Quebec City, 2010.

File “Young+Lurmann_1984_ERT_vol7.pdf”  ‒  Copy of  report

Young, J. R. and Lurmann, F. W.: ADOM/TADAP Model Development Program: Volume 7. Aqueous-Phase Chemistry, ERT Document P-B980-535, June, Environmental Research & Technology, Inc., Newbury Park, California, 135 pp., 1984.

Other Information: 

Version 4.1 of the Canadian Forest Fire Emissions Processing System (CFFEPS) can estimate biomass burning emissions over North America based on near-real-time satellite-retrieved hotspot information.  CFFEPS v4.1 was used by the RAQDPS-FW023, the version of the RAQDPS023 that includes biomass burning emissions (see Moran et al., 2025).  The CFFEPS v4.1 source code is available at https://doi.org/10.5281/zenodo.15305591.  More information about CFFEPS can be found in Chen et al. (2019).

GEM-MACH v3.1.1.2 source code for the RAQDPS024, an equivalent version to the RAQDPS023 that went into operation after a migration to a new ECCC high-performance computer system in June 2022 (Moran et al., 2025), is available at https://zenodo.org/records/13952893.

References:

Chen, J., Anderson, K., Pavlovic, R., Moran, M.D., Englefield, P., Thompson, D.K., Munoz-Alpizar, R., and Landry, H.: The FireWork v2.0 air quality forecast system with biomass burning emissions from the Canadian Forest Fire Emissions Prediction System v2.03, Geosci. Model Dev., 12, 3283–3310, https://doi.org/10.5194/gmd-12-3283-2019, 2019.

Moran, M.D., Savic-Jovcic, V., Stroud, C.A., Ménard, S., Gong, W., Zhang, J., Zheng, Q., Chen, J., Akingunola, A., Lupu, A., Menelaou, K., and Munoz-Alpizar, R.: Operational chemical weather forecasting with the ECCC online Regional Air Quality Deterministic Prediction System version 023 (RAQDPS023) – Part 1: System description, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-4323, 2025.