Change long name specifier for CO2 forcings

[billsacks]

Description of changes

We have decided to use the CESM2 scheme for this.

See ESCOMP/CMEPS#658 for some relevant discussion.

I did this with two regex search & replaces:

(1) Concentration-driven:

• Search for <lname>([^_]*)C_(.*)</lname>
• Replace with <lname>$1_$2_BGC%BDRD</lname>

(2) Emissions-driven:

• Search for <lname>([^_]*)E_(.*)</lname>
• Replace with <lname>$1_$2_BGC%BPRP</lname>

This will need to be coordinated with a few component changes, coming soon.

• It is important that this be coordinated with a CAM PR - either Change specification for CO2 concentration-driven compsets - option 1 CAM#1583 or Change specification for CO2 concentration-driven compsets - option 2 CAM#1584 (whichever of those is deemed to be correct)

Specific notes

Contributors other than yourself, if any: none

Fixes: none

User interface changes?: No

Expected answer changes: I think that any compset that now has a _BGC specifier will change answers. (Answer changes may not show up in testing if we don't have any tests of B1850E or BHISTE compsets.)

Testing performed (automated tests and/or manual tests):
None yet!

[billsacks]

@klindsay28 - can you please look over these changes and verify that I have made the correct changes to the compsets?

@briandobbins - FYI

[billsacks]

I originally did this with two regex search & replaces:

(1) Concentration-driven:

• Search for <lname>([^_]*)C_(.*)</lname>
• Replace with <lname>$1_$2_BGC%BDRD</lname>

(2) Emissions-driven:

• Search for <lname>([^_]*)E_(.*)</lname>
• Replace with <lname>$1_$2_BGC%BPRP</lname>

But it sounds like we may be using CONC / EMIS rather than BDRD / BPRP, so I changed those in a follow-up commit.

[billsacks]

I'm changing this to a draft because it sounds like the exact specifier (CONC / EMIS, BDRD / BPRP, ...) is still under discussion.

[billsacks]

Based on discussion this morning, we're going to use _BGC%BDRD and _BGC%BPRP after all, so I have reverted to those specifiers and marked this ready for review. This will need to be coordinated with at least a CAM tag... I'll figure out all the component coordination needed soon.

[billsacks]

@klindsay28 - based on our recent discussion, I'm questioning whether I did the right thing here with the concentration-driven compsets: My initial thinking was that I should change the comcentration-driven compsets to BDRD, but based on our discussion a couple of days ago, should those actually have no _BGC specifier?

[billsacks]

@klindsay28 - based on our recent discussion, I'm questioning whether I did the right thing here with the concentration-driven compsets: My initial thinking was that I should change the comcentration-driven compsets to BDRD, but based on our discussion a couple of days ago, should those actually have no _BGC specifier?

@klindsay28 - also a similar question for CAM: do you know if these compsets should have _BGC%BDRD or no _BGC specifier?:

https://github.com/ESCOMP/CAM/blob/9e9c1371e6c3b8aafa6d1c7480cac7988335f163/cime_config/config_compsets.xml#L437-L469

[billsacks]

@klindsay28 - based on our recent discussion, I'm questioning whether I did the right thing here with the concentration-driven compsets: My initial thinking was that I should change the comcentration-driven compsets to BDRD, but based on our discussion a couple of days ago, should those actually have no _BGC specifier?

@klindsay28 - also a similar question for CAM: do you know if these compsets should have _BGC%BDRD or no _BGC specifier?:

https://github.com/ESCOMP/CAM/blob/9e9c1371e6c3b8aafa6d1c7480cac7988335f163/cime_config/config_compsets.xml#L437-L469

Looking into this a little more myself, I see that most of the B compsets in CESM2 had _BGC%BDRD; this makes me think that _BGC%BDRD may be the right thing to do here, too. (However, I see that the WACCM compsets did not have any _BGC specifier in CESM2.) But most F compsets in CESM2 did not have a _BGC specifier, so I'm wondering if that behavior should be maintained for CESM3 as well??

But my confidence here is very low, so I'm looking forward to clarity from @klindsay28.

[mvertens]

@billsacks - my understanding is that _BGC%BDRD or _BGC%BPRP turns on an emission driven scenario (based on triggering CO2C) and the lack of _BGC%XXX triggers concentration driven scenario (based on triggering COA). This can also be seen based on what happens in CAM with co2_cycle. I'm happy to chat about this.

[gold2718]

@billsacks,
_BGC%BDRD is emission driven but CO2 is radiatively passive (implemented by setting co2_cycle_rad_passive=.true. in CAM_NAMELIST_OPTS which sets CO2 as a passive species in the rad_climate namelist variable).

[billsacks]

@mvertens and @gold2718 - thank you both for this input! I think the main question at this point is: what is the intent for CESM3? Based on what you two have said and the understanding I've gotten from conversations with @klindsay28, I'm starting to think that the intent is that the compsets that previously had a C at the end of the time period should now have no _BGC specifier. I'd like confirmation from @klindsay28 on that. Note that that would mean that we currently don't have any _BGC%BDRD compsets, in contrast to CESM2, where most B compsets were _BGC%BDRD. I'll push a commit here that makes this change, for review.

I'm also realizing that there will probably be answer changes to any compset that now has a _BGC specifier, since this specifier changes behavior in various components. That means that at least the emissions-driven compsets - with BGC%BPRP - will change answers. If the concentration-driven compsets map to having no BGC specifier, then I think they won't change answers, but if they map to BGC%BDRD then I think they'll change answers, too.

[billsacks]

I'm also realizing that there will probably be answer changes to any compset that now has a _BGC specifier, since this specifier changes behavior in various components. That means that at least the emissions-driven compsets - with BGC%BPRP - will change answers. If the concentration-driven compsets map to having no BGC specifier, then I think they won't change answers, but if they map to BGC%BDRD then I think they'll change answers, too.

Oh, it looks like we currently don't have any tests of the B1850E or BHISTE compsets, so I think that the latest version of this PR (which maps concentration-driven compsets to no BGC specifier) should be bit-for-bit in testing.

I like the idea that this will be bit-for-bit in testing, partly because I'd like to be assured that the changes to the compset matches in RUN_STARTDATE don't change answers for any tests.