GCAP 2.0 is set for inclusion into the GEOS-Chem standard code in version 13.1. Until then, one may obtain the beta release code in version 13.0.0 using the following commands.
git clone -b feature/GCAP2 https://github.com/ltmurray/GCClassic.git ./Code.GCAP2 cd Code.GCAP2 git submodule update --init --recursive cd src/GEOS-Chem git checkout feat/GCAP2 cd ../HEMCO git checkout feat/GCAP2
Note that submodules always download in a headless state, requiring one to manually select a branch as above.
The GCAP 2.0 meteorology and emission files are located at http://atmos.earth.rochester.edu/input/gc/ExtData/, to which you can set remote_root in the download_data.py python script.
Please contact Dr. Murray with any questions or to report any issues.