HEMCO (Harmonized Emissions Component; Keller et al., 2014, Lin et al., 2021) is an emissions tool that calculates emissions at runtime, providing selection of inventory, scaling, masking, and interpolation to the model grid and time as configured by a text-based configuration file. It avoids lengthy pre-processing of emission files for the entire duration of the model run, and allows for reproducibility of the emissions processing workflow by sharing the configuration file and original source files.
HEMCO can be enabled in CAM-chem compsets by adding the namelist parameter use_hemco = .true., or appending _HCO to the compset name. HEMCO is the only emissions option available for GEOS-Chem chemistry.
The HEMCO configuration file (HEMCO_Config.rc) describes the relationship between the source input data and the emissions to be provided to the model. In CAM-chem, the configuratin file is specified through the namelist option hemco_config_file; a copy of the default file can be edited for your model run. General HEMCO documentation is available at https://hemco.readthedocs.io/. In GEOS-Chem, the configuration file in the case directory is always used.
HEMCO in CESM, as of 2023-10-11:
Note there are reproducibility issues: https://github.com/ESCOMP/HEMCO_CESM/issues/31
Older version: Nov 2022:
"Model cam missing file hemco_config_file = '/glade/scratch/hplin/2211_camchem_2.2_ne0korus/run/HEMCO_Config.rc.1'"
- Please make sure to update user_nl_cam's hemco_config_file parameter to point to your own "run" directory in scratch! This is where the HEMCO_Config.rc and HEMCO_Diagn.rc files are downloaded to during the steps in slide 29.
- Sample configuration files are available in https://github.com/jimmielin/HEMCO_CESM_configs/ and you may customize your own HEMCO_Config.rc file to specify emissions, following the slides and the HEMCO User's Guide: https://hemco.readthedocs.io/en/stable/hco-ref-guide/hemco-config.html.