Import of high order turbulence closure scheme

[Shusuke Nishimoto (mo-snishimoto)]

PR Summary

Sci/Tech Reviewer: Adrian Lock (@Adrian-Lock)
Code Reviewer: Matthew Hambley (@MatthewHambley)

This PR imports high order turbulence closure scheme (3DTE Mk1 scheme) in UM to LFRic.

Please see #46 for details, documentation and extra tests performed.

Linked PRs

• https://github.com/MetOffice/lfric-jedi/pull/1335

Code Quality Checklist

• I have performed a self-review of my own code
• My code follows the project's style guidelines
• Comments have been included that aid understanding and enhance the readability of the code
• My changes generate no new warnings
• All automated checks in the CI pipeline have completed successfully

Testing

• I have tested this change locally, using the LFRic Apps rose-stem suite
• If any tests fail (rose-stem or CI) the reason is understood and acceptable (e.g. kgo changes)
• I have added tests to cover new functionality as appropriate (e.g. system tests, unit tests, etc.)
• Any new tests have been assigned an appropriate amount of compute resource and have been allocated to an appropriate testing group (i.e. the developer tests are for jobs which use a small amount of compute resource and complete in a matter of minutes)

trac.log

Test Suite Results - lfric_apps - test_3dte_mk1/run2

Suite Information

Item	Value
Suite Name	test_3dte_mk1/run2
Suite User	shusuke.nishimoto
Workflow Start	2026-09-09T18:28:40
Groups Run	all

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.07.1	True
jules	MetOffice/jules@2026.07.1	True
lfric_apps	mo-snishimoto/lfric_apps@3dte_mk1	False
lfric_core	MetOffice/lfric_core@3e965e8	True
moci	MetOffice/moci@2026.07.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@77a5166	True
socrates	MetOffice/socrates@2026.07.1	True
socrates-spectral	MetOffice/socrates-spectral@2026.07.1	True
ukca	MetOffice/ukca@9fc2b6d	True

Task Information

❌ failed tasks - 2

Task	State
check_lfric_atm_3dte-seuk_MG_azspice_gnu_fast-debug-32bit	failed
check_lfric_atm_3dte-seuk_MG_ex1a_cce_fast-debug-32bit	failed

✅ succeeded tasks - 1609

⌛ waiting tasks - 2

Task	State
housekeep_azspice	waiting
housekeep_ex1a	waiting

Security Considerations

• I have reviewed my changes for potential security issues
• Sensitive data is properly handled (if applicable)
• Authentication and authorisation are properly implemented (if applicable)

Performance Impact

• Performance of the code has been considered and, if applicable, suitable performance measurements have been conducted

AI Assistance and Attribution

• Some of the content of this change has been produced with the assistance of Generative AI tool name (e.g., Met Office Github Copilot Enterprise, Github Copilot Personal, ChatGPT GPT-4, etc) and I have followed the Simulation Systems AI policy (including attribution labels)

Documentation

• Where appropriate I have updated documentation related to this change and confirmed that it builds correctly

PSyclone Approval

• If you have edited any PSyclone-related code (e.g. PSyKAl-lite, Kernel interface, optimisation scripts, LFRic data structure code) then please contact the TCD Team

Sci/Tech Review

• I understand this area of code and the changes being added
• The proposed changes correspond to the pull request description
• Documentation is sufficient (do documentation papers need updating)
• Sufficient testing has been completed

(Please alert the code reviewer via a tag when you have approved the SR)

Code Review

• All dependencies have been resolved
• Related Issues have been properly linked and addressed
• CLA compliance has been confirmed
• Code quality standards have been met
• Tests are adequate and have passed
• Documentation is complete and accurate
• Security considerations have been addressed
• Performance impact is acceptable

[iboutle]

A few comments below. Thanks!

[Shusuke Nishimoto (mo-snishimoto)]

Hi iboutle, Thank you for the careful check and comments.
I fixed my branch, following your comment.
I also confirmed this change doesn't affect KGOs.

[iboutle]

Thanks, looks good to me now. Just to note the KGO change for the coupled model should disappear when this is merged up to the head of main

[DanStoneMO]

This needs a linked PR in JEDI, which is now up at: https://github.com/MetOffice/lfric-jedi/pull/1335

[Shusuke Nishimoto (mo-snishimoto)]

This needs a linked PR in JEDI, which is now up at: https://github.com/MetOffice/lfric-jedi/pull/1335

Thanks for the comment. I edited the PR summary to include it.

[Adrian Lock (Adrian-Lock)]

First many thanks for the very helpful "namelist_and_diagnostics.pdf" and "code_change_detail.pdf" documentation on the accompanying issue. In addition to my comments on the files, I have two further comments:

I apologise for my most significant proposal, which is to use more meaningful names for the two turbulence schemes than the old UM "9C" and "1A", which unfortunately has quite far reaching consequences. I am very happy to take other suggestions but my proposal is to use "Kprof" and "HoC", respectively.

I like having the "blending" options in the blayer namelist, rather than mixing - as long as everyone else is happy that's good.  I'll note explicitly, though, the up-coming clash with my PR #752 where I've added a new blending option

Overall, even if simply porting code from the UM, the interfacing and coupling with the rest of lfric is a very impressive piece of work. Many thanks again.

[Adrian Lock (Adrian-Lock)]

Thank you so much for all that relabeling of the scheme names.

Apologies if I missed it, but it would be good to open an issue to port UMDP 25, that describes this scheme, to the new lfric documentation area. No need to get that port done as part of this PR.

[Shusuke Nishimoto (mo-snishimoto)]

Thank you so much for looking the code again and the approvement.

Though I am prepared for the possibility that further conflict resolution with #714 and #752 might be required depending on the timing of the merge, I also have merged the latest main and resolved conflicts in the following files, heading for merge:

• science/gungho/rose-meta/lfric-gungho/rose-meta.conf
• science/gungho/rose-meta/lfric-gungho/versions.py

I also modified following unit-tests in the same way as #725 and #752 , (reflected mixing namelsit change to feign_mixing_config subroutine):

• science/gungho/unit-test/kernel/diffusion/diffusion_momentum_flux_kernel_mod_test.pf
• science/gungho/unit-test/kernel/diffusion/divergence_momentum_flux_kernel_mod_test.pf

I confirmed rose-stem (all) suite ends successfully and KGO change for the coupled model disappeared as Ian said above.
I updated KGO files of 3dte tests since they are affected by the merge of #656 .
I replaced trac.log in the ticket summary with the latest one.

Apologies if I missed it, but it would be good to open an issue to port UMDP 25, that describes this scheme, to the new lfric documentation area. No need to get that port done as part of this PR.

Thank you for the suggestion.
Yes, I would love to try converting UMDP 25 into LFRic documentation in another PR.