Updates to RRTMG code to improve/implement cloud feedbacks

[trudeeidhammer]

TYPE: enhancement

KEYWORDS: cloud interaction with radiation, added namelist options, added calculation of 3d cloud fraction

SOURCE: Trude Eidhammer

DESCRIPTION OF CHANGES: 1) Fixed a bug which caused RRTMG short wave code to not interact with clouds. 2) User can now chose the iCloud option to use and the time step between RRTMG update in the namelist. 3) Added the Thompson routine of calculating 3D cloud fraction from WRF

TESTS CONDUCTED:

Compared the updates with the simple radiation scheme, and with icloud = 0 (icloud=0 means no cloud impact on radiation)

Figure shows 2m average daily temperature difference (in Kelvin). Left plot is the difference between RRTMG icloud =3 and the simple radiation scheme. Right plot is the difference between RRTMG icloud=3 and RRTMG icloud=0

Checklist

Merging the PR depends on following checklist being completed. Add X between each of the square brackets if they are completed in the PR itself. If a bullet is not relevant to you, please comment on why below the bullet.

• [X ] Closes issue #xxxx n/a
• [X] Tests added (unit tests and/or regression/integration tests)
• [X] Backwards compatible
• [X] Requires new files? No
• [X] Fully documented

[gutmann]

Thanks, can you fix the compile error:

utilities/atm_utilities.f90:942:14:
  942 |         ax_iwc = ABS(qvs(k2)-qvs(k1))
      |              1
Error: Symbol ‘ax_iwc’ at (1) has no IMPLICIT type; did you mean ‘max_iwc’?

[gutmann]

Can you fix it so that it won't crash with different physics options (e.g. no radiation and simple microphysics) I don't think you actually need the where statement on line 230 anymore anyway right?