The Community Terrestrial Systems Model.
This includes the Community Land Model (CLM5 and CLM4.5) of the Community Earth System Model.
For documentation, quick start, diagnostics, model output and references, see
http://www.cesm.ucar.edu/models/cesm2.0/land/
and
https://escomp.github.io/ctsm-docs/
For help with how to work with CTSM in git, see
https://github.com/ESCOMP/ctsm/wiki/Recommended-git-setup
and
https://github.com/ESCOMP/ctsm/wiki/Getting-started-with-CTSM-in-git