ctsm5.4.027

[CTSM Gatekeeper]

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Tag name: ctsm5.4.027
Originator(s): erik (Erik Kluzek,UCAR/TSS,303-497-1326)
Date: Tue Mar 24 10:50:35 PM MDT 2026
One-line Summary: Some final namelist default changes needed

Purpose and description of changes
----------------------------------

Some important final answer changes needed for the coupled model to get the right parameter file and to set n_melt_glcmec=1 for clm6_0.

Also use the 2015 finidat file for SSP future scenarios. And fix some of the namelist picking for finidat files, especially for: 2003, 2010, and 2015.

Significant changes to scientifically-supported configurations
--------------------------------------------------------------

Does this tag change answers significantly for any of the following physics configurations?
(Details of any changes will be given in the "Answer changes" section below.)

[Put an [X] in the box for any configuration with significant answer changes.]

[X] clm6_0

[ ] clm5_0

[ ] ctsm5_0-nwp

[ ] clm4_5


Bugs fixed
----------

List of CTSM issues fixed (include CTSM Issue # and description) [one per line]:

Fixes #3799 -- clm6_0_cam7.0 tuning mode is NOT getting the right parameter file
Fixes #3824 -- Change n_melt_glcmex to 1 for clm6_0
Fixes #3826 -- Add an IC file for 2015 for ISSP/CMIP6 cases
Fixes #3835 -- 2010 finidat files not being used because not listed in init_interp_sim_years
Fixes #3836 -- 2003 finidat not working correctly, needs do_transient_pfts==TRUE

Notes of particular relevance for users
---------------------------------------
Changes made to namelist defaults (e.g., changed parameter values):
n_melt_glcmec is now 1 for clm6_0 rather than 10 for everything else
coupled parameter file gets picked when LND_TUNING_MODE == clm6_0_cam7.0

Changes to the datasets (e.g., streams, surface or initial files):
finidat file for clm4_5/clm5_0 2015 start

Notes of particular relevance for developers:
---------------------------------------------
Caveats for developers (e.g., code that is duplicated that requires double maintenance):
Limited work to make the finidat picking funciton better

Changes to tests or testing:
Removed the need to explicitly set an finidat file for a few testmods

Contributors: @slevis-lmwg

Testing summary: regular
----------------
[PASS means all tests PASS; OK means tests PASS other than expected fails.]

build-namelist tests (if CLMBuildNamelist.pm has changed):

derecho - OK

python testing (if python code has changed; see instructions in python/README.md; document testing done):

derecho - PASS

regular tests (aux_clm: https://github.com/ESCOMP/CTSM/wiki/System-Testing-Guide#pre-merge-system-testing):

derecho ----- OK
izumi ------- OK

If the tag used for baseline comparisons was NOT the previous tag, note that here:


Answer changes
--------------

Changes answers relative to baseline: Yes (for clm6_0 and possibly some clm4_5)

Summarize any changes to answers, i.e.,
- what code configurations: clm6_0, and some clm4_5 for finidat file picking
- what platforms/compilers: All
- nature of change: slightly modified climate
clm6_0:
n_melt_glcmec changes answers for all simulations
parameter file changes answers when coupled (or using a CAM lnd_tuning_mode)
finidat picking changes cases affected
clm4_5:
using single precision n_melt_glcmec may have a small change to answers
finidat picking changes cases affected

If this tag changes climate list the run(s) done to evaluate the new
climate. Preferably in https://github.com/NCAR/LMWG_dev (or give details below)
- CESM_dev issue number(s): 304 (turns n_melt_glcmec=1 in a coupled simulation)

Other details
-------------

Pull Requests that document the changes (include PR ids):
(https://github.com/ESCOMP/ctsm/pull)
@3810 -- Important coupled model final answer changes: param file and n_melt_glcmec

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