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ctsm5.4.056: Merge wetlands.n04.ctsm5.4.055 to master - #4204

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ctsm5.4.056: Merge wetlands.n04.ctsm5.4.055 to master#4204
slevis-lmwg wants to merge 54 commits into
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slevis-lmwg:wetlands.n04.ctsm5.4.055

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@slevis-lmwg slevis-lmwg commented Sep 9, 2026

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Description of changes

Merging the wetlands branch to master. HOWEVER, the wetlands branch has these tags...

branch_tags/wetlands.n01.ctsm5.4.029
branch_tags/wetlands.n02.ctsm5.4.029
branch_tags/wetlands.n03.ctsm5.4.029
branch_tags/wetlands.n03.ctsm5.4.044
branch_tags/wetlands.n04.ctsm5.4.044
branch_tags/wetlands.n04.ctsm5.4.054
branch_tags/wetlands.n05.ctsm5.4.054

...and instead we want wetlands.n04.ctsm5.4.055 merged to master. This PR accomplishes that without explicitly merging or tagging anything new in the wetlands branch.

Look at code and param diffs and talk to Sean for more info:

  1. Changes to snow-covered fraction and inundated fraction where they overlap.
  2. Changes to the methane parameterization:
    Best evaluation of these first two changes.
  3. Changes to phenology to improve high-lat survivability, allows plants to green up after the summer solstice:
    Best evaluation of the third change.

Specific notes

Contributors other than yourself, if any:
@swensosc @wwieder @lifang0209 ...

CTSM issues resolved or otherwise addressed, if any:
I don't think there's a corresponding issue.

If answers are expected to change, describe (delete this line otherwise):
The wetlands branch will change answers relative to the master branch. Subtle change in climate expected, mainly through change in albedo.

Any user interface changes (namelist or namelist defaults changes)?
Did we change paramfiles with the wetlands branch or using same as on master?

Testing planned or performed, if any:

  • ./run_sys_tests -s aux_clm -c ctsm5.4.055 -g ctsm5.4.056
    • derecho
    • izumi: DIFFs from the baseline as expected
    • consider comparing against the wetlands baseline if dynbal is the only update, since it will mean fewer DIFFs
  • ./run_sys_tests -s ctsm_sci -c ctsm_sci-ctsm5.4.054 -g ctsm_sci-ctsm5.4.056 derecho only
  • probably ctsm_sci was not necessary for this tag and cesm testlists will likely be run with the next tag

Requirements before merge:

swensosc and others added 30 commits March 4, 2026 09:28
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Removing whitespace; sorry, I should have done this for all the lines that needed it in one commit, but now I'm on a roll...
ekluzek and others added 10 commits June 11, 2026 13:58
wetlands.n03.ctsm5.4.044: Wetlands update to ctsm5.4.044
wetlands.n04.ctsm5.4.044: Change seasonal deciduous onset
Update submodules to the latest needed for cesm3_0_alpha10a

Update submodules: ccs_config, cime, cdeps, cmeps, share
Current latest submodules that will be coming in cesm3_0_beta10

cesm3_0_beta09 had: cime6.4.1, share1.0.21, cdeps1.0.101, cmeps1.1.54

Also fix the two multi-instance tests that were failing, by making sure DGLC couples less times than ROF.

And add new ctsm_release testlist which runs every test. And make sure the list of tests that should be subsets of aux_clm or ctsm_sci are so (as well as fates, and crop_cal). And bring in a script that checks the testlist for these features and will also fix them. And bring that script into a github workflow so the testlist is checked for basic requirements.
wetlands.n04.ctsm5.4.054: Merge master 20260901 to wetlands
Add temporal smoothing of DYNBAL conservation correction fluxes

Spread the DYNBAL water and energy fluxes over many years: Rather than releasing all of
the DYNBAL fluxes in the year in which they're generated, instead put them in storage
pools that are released with a 20-year residence time (controllable via a new namelist
parameter; the default for CLM50 is set to 0.75 to maintain something closer to the old
behavior). This reduces these fluxes, especially in the oscillatory case that is somewhat
common with a dynamic ice sheet.

The new storage pools are reset when reset_dynbal_baselines is set to .true., since this
feels conceptually similar to the other resetting done by that flag, so it feels
appropriate to do this resetting at the same time.

This tag also changes the sign convention for the DYNBAL fluxes: the previous sign
convention was unintuitively the opposite of the sign convention of other fluxes to
river/atm; while I'm changing these fluxes anyway, I'm also flipping the sign convention
to be more intuitive and hopefully less error-prone.

The motivation for this change is: When subgrid areas change due to dynamic landunits /
columns, fluxes are generated to compensate for changes in gridcell-average water and
energy (QFLX_LIQ_DYNBAL, QFLX_ICE_DYNBAL, EFLX_DYNBAL). These fluxes can (and should) be
reduced via careful setting of reset_dynbal_baselines, but that still doesn't reduce these
fluxes to zero. The previous implementation seems good enough in situations where there is
a gradual change in a given grid cell's subgrid areas over many years. Unfortunately,
though, that is not always the situation when coupling to CISM, as has been seen in recent
CESM3 runs: In grid cells around the ice sheet margin, large fractions of a CTSM grid cell
can blink between mostly-vegetated/bare and mostly-glacier on a 2-year cycle, and this
oscillatory behavior can go on for many years, possibly indefinitely. This can lead to
large dynbal fluxes in each year, even when dribbled throughout the year (as was
previously done). It is problematic for the ocean to get negative dynbal fluxes, but it is
also problematic to remove these negative dynbal fluxes by spreading them globally, as is
currently done, because then regional fluxes that should average to 0 spatially and
temporally (e.g., into the Arctic ocean) end up being biased positive. This PR implements
a relatively easy partial fix, which particularly addresses the oscillatory case that
seems to be a common cause of the observed ice runoff. See
ESCOMP#4188 for more details.
@slevis-lmwg slevis-lmwg self-assigned this Sep 9, 2026
@slevis-lmwg slevis-lmwg added enhancement new capability or improved behavior of existing capability priority: high High priority to fix/merge soon, e.g., because it is a problem in important configurations science Enhancement to or bug impacting science PR status: needs testing non-b4b Changes answers (incl. adding tests) test: aux_clm Pass aux_clm suite before merging test: ctsm_sci Run and check ctsm_sci suite before merging labels Sep 9, 2026
@github-project-automation github-project-automation Bot moved this to Ready to start (or start again) in CTSM: Upcoming tags Sep 9, 2026
@slevis-lmwg slevis-lmwg changed the title Merge wetlands.n04.ctsm5.4.055 to master ctsm5.4.056: Merge wetlands.n04.ctsm5.4.055 to master Sep 9, 2026
@slevis-lmwg slevis-lmwg moved this from Ready to start (or start again) to In progress - master in CTSM: Upcoming tags Sep 9, 2026
@slevis-lmwg slevis-lmwg moved this from Todo to In Progress in LMWG: Sprint Planning Board Sep 9, 2026
@slevis-lmwg
slevis-lmwg marked this pull request as ready for review September 9, 2026 23:51
@slevis-lmwg
slevis-lmwg requested a review from swensosc September 9, 2026 23:52
@slevis-lmwg

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@swensosc my PR to merge the wetlands branch to master is ready for your review:

  • Please look at my ChangeLog attempt
  • Let me know of any other concerns you may have with this PR
  • We hope to merge this and tag ctsm5.4.056 by Thursday p.m. (Friday a.m. OK) to enable next steps in an upcoming CESM tag

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I approve this PR.

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enhancement new capability or improved behavior of existing capability non-b4b Changes answers (incl. adding tests) PR status: needs testing priority: high High priority to fix/merge soon, e.g., because it is a problem in important configurations science Enhancement to or bug impacting science test: aux_clm Pass aux_clm suite before merging test: ctsm_sci Run and check ctsm_sci suite before merging

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