Change nextsw_cday calculation for cam_dev (CAM7) in cplhist mode

[olyson]

Description of changes

The radiation re-ordering in cam_dev (CAM7) requires a change to the calculation of nextsw_cday in cplhist mode. This PR introduces a new namelist variable, nextsw_cday_calc, which controls this behavior. The default value is appropriate for cplhist files generated with CAM7. Note that, by default, this namelist flag has no effect on non-cplhist cases (because of the default value of iradsw in non-cplhist cases).

Specific notes

Contributors other than yourself, if any: @billsacks @adamrher

CDEPS Issues Fixed (include github issue #):

Are there dependencies on other component PRs (if so list):

Are changes expected to change answers (bfb, different to roundoff, more substantial): Greater than roundoff-level changes in cases using datm in CPLHIST mode.

Any User Interface Changes (namelist or namelist defaults changes): New namelist variable, nextsw_cday_calc.

Testing performed (e.g. aux_cdeps, CESM prealpha, etc):
I have plugged this branch into the latest version of CTSM and ran the following tests:

• SMS_D_Ld3.f10_f10_mg37.I1850Clm50BgcCrop.derecho_intel.clm-default - passes and bit-for-bit
• SMS_D_Ld1.ne30pg3_t232.I1850Clm50BgcSpinup.derecho_intel.clm-cplhist - passes but changes answers as expected
• SMS_D_Ld1.ne30pg3_t232.I1850Clm50BgcSpinup.derecho_intel.clm-cplhist, with the new namelist flag changed to "cam6" - passes and bit-for-bit

Hashes used for testing:
ctsm5.3.009

[billsacks]

This is still on my radar, but other priorities have come up that have prevented me from working on this. I still will work on this, but it may not be until after some vacation and the CESM workshop – so in late June or July.

[wwieder]

@billsacks it seems like @olyson may need help with namelist changes associated with this PR? If we're going to start running with CPL_HIST with CESM3 output soon, this should likely be addressed.

[billsacks]

Yes. Sorry for the continued delay on this. It is coming up to the top of my list.

[billsacks]

Ack! Things have gotten away from me lately but I'm looking into this now.

[billsacks]

Ack! Finally got to this after way too long of a delay! Sorry!

@olyson and @adamrher thank you for these changes! With the additions I've done here, I'm happy with this myself.

@olyson and/or @adamrher - can one of you please look over my changes - especially the description of the new namelist flag - and let me know if this looks good to you? Once you give your okay, I'll merge it.

[billsacks]

I have plugged this branch into the latest version of CTSM and ran the following tests:

• SMS_D_Ld3.f10_f10_mg37.I1850Clm50BgcCrop.derecho_intel.clm-default - passes and bit-for-bit
• SMS_D_Ld1.ne30pg3_t232.I1850Clm50BgcSpinup.derecho_intel.clm-cplhist - passes but changes answers as expected
• SMS_D_Ld1.ne30pg3_t232.I1850Clm50BgcSpinup.derecho_intel.clm-cplhist, with the new namelist flag changed to "cam6" - passes and bit-for-bit

[billsacks]

@olyson and @adamrher - I have also updated the top-level comment in this PR.

[adamrher]

@billsacks thanks for circling back to this. The namelist description looks great -- I'm glad that you made it clear that 'cam6' refers to the driver ordering in cam6 physics and earlier physics versions.

[olyson]

Thanks for getting back to this. Looks good to me, especially the detailed comments/descriptions.