CCPP-ize PUMAS

[nusbaume]

This issue is here to help track the CCPP-ization of the current CAM interface to the PUMAS microphysics package, with the eventual goal of having a version of PUMAS runnable in CAM-SIMA.

Also notifying @Katetc and @andrewgettelman that I'll start work on this soon, and so may have some questions for them at some point.

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The following is a list of needed tasks to assist with tracking progress on PUMAS CCPP-ization:

Tasks needed explicitly in the ESCOMP/PUMAS repo:

• Remove all uses of CESM-specific source code from internal PUMAS routines (except the qsat_X routines, which will need to be a dependency).
• Create a CCPP cap for the main PUMAS routine (and ensure it works in CAM).
• Create Metadata files for the PUMAS CCPP cap and the "proc_rates_type" DDT.
• Create Github Action which validates the metadata files whenever a PR is made.
• Add PUMAS submodule to NCAR/ccpp-physics repo, along with needed dependencies.

Tasks needed for a complete PUMAS interstitial scheme that lives in NCAR/ccpp-physics:

• Register all constituents needed by PUMAS.
• Subset variables into expected microphysics dimensions (e.g. subcolumns, when enabled).
• Convert microphysics-dimensioned variables back into regular-dimensioned variables.
• Apply any associated tendencies to their states, possibly in several subcycling steps.
• Calculate (and apply if necessary) the "final", post-subcycle microphysics tendencies.
• Calculate size distribution parameters and Liquid Water Path needed for diagnostics and radiation (i.e. the size_dist_param_X subroutine calls in CAM)
• Calculate remaining diagnostic variables, such as precipitation efficiency.
• Output diagnostics using CAM-SIMA-specific method (non-portable)

Tasks needed to fully-implement a CCPP-ized PUMAS in ESCOMP/CAM-SIMA :

• Create a CAM-SIMA-specific pumas_namelist.xml file to support PUMAS namelist variables in CAM-SIMA.
• Develop the correct directory structure between PUMAS, ccpp-physics, atmospheric_physics, and CAM-SIMA, which will likely require at least small modifications in all repos.
• Create a PUMAS SDF needed to properly test PUMAS in CAM-SIMA and implement it in the CAM7 SDF. This will likely include the use of the "subcyle" CCPP-framework feature.

Any additional tasks that are discovered during the development process will be added to this list accordingly.