[WIP] Added support for importing mass flux from ExtData

[LiamBindle]

This PR includes 5 major changes:

1. Added support for driving GCHP with native GEOS metfields. #164
2. Changes tracer advection to total VMR rather than dry VMR. The conversion to/from total VMR is done at the start/end of AdvCoreGridComp::Run().
3. Added IMPORT_MASS_FLUX_FROM_EXTDATA as a field in GCHP.rc. If .true., GCHPenvGridComp imports MF[XY]C and C[XY]C from ExtData and converts them to real8's. If .false., GCHPenvGridComp calculates MF[XY]C and C[XY]C from wind and pressure. Both ways export MF[XY] and C[XY] real8's which are imported in AdvCoreGridComp.
4. Refactored GCHPenvGridComp::Run to improve readability.
5. [WIP] Add diagnostic for upwards mass flux #96

These are meant to be a clean and up-to-date implementation of the original mass flux simulation whose diff is here.

[LiamBindle]

So far I've tested this with 24-hour transport tracer simulations driven by GEOS-IT data (a wind-based simulation versus a mass-flux-based simulation).

I still need to add a "mass flux simulation", as of bc42091 the necessary code-updates should be there.

@sdeastham Could you review this diff when you have a chance? A thorough check-over of the diffs to AdvCore_GridCompMod.F90 would be greatly appreciated. You can ignore the diffs to geos-chem and HEMCO submodules since those are from #164, and the diff to GCHP_GridCompMod.F90 is just plumbing.

For reference, here is the diff of the original mass flux simulation which is what I based this PR on.

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[sdeastham]

I've reviewed this pull request and can confirm that it appears to work as intended.

EDIT: Never mind! Came across a potential issue while reviewing.

[sdeastham]

I think that the computation of mass fluxes when winds are read in is incorrect, since all advection is now performed using total VMRs rather than dry VMRs.

[lizziel]

I have a general question about the description of this PR. Tracer advection uses mass mixing ratio so why is the term VMR used?

[lizziel]

Is there an FVdycore PR in the works for the changes to AdvCore_GridComp?

[LiamBindle]

Thanks Seb and Lizzie for your reviews! I'll make those updates early next week.

Regarding VMR vs mass mixing ratio, that's just a terminology mistake on my part. I just meant to differentiate between total and dry mixing ratios.

Regarding a PR for AdvCore_GridComp, I'm not planning to.

[lizziel]

Why not do a PR for FVdycore? When resolving conflicts down the road during upstream version update it might useful to have around.

[LiamBindle]

@lizziel I did a pretty extensive refactor of GCHPctmEnv_GridComp (summarized in #181 if you want to see the diff). I merge it into this PR. I added the _IMPORT and _EXPORT suffixes, removed quite a bit of legacy code that wasn't used anymore, and I also reformatted the file. Could you take a look when you have a chance and let me know what you think?

[lizziel]

Looks good. See my review at #181.

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[LiamBindle]

Closed in favor of #190