Improvements to tke diagnostic

[Adrian Lock (Adrian-Lock)]

PR Summary

Sci/Tech Reviewer: MichaelWhitall
Code Reviewer: Cameron Bateman (@cameronbateman-mo)

The boundary layer scheme diagnoses a vertical velocity variance (w_var, and thence turbulent kinetic energy, TKE) that is used by other physics parametrizations to quantify subgrid variability. In the CoMorph convection scheme, for example, the ratio Km/sqrt(w_var) is used as the turbulence length-scale. However, issues with both the local and non-local contributions to TKE have been identified and those are corrected here. The corrections are controlled via the namelist logocal improved_tke_diag

Equivalent changes in the UM: vn14.1_improve_tke_diag

closes #232

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 - main905c_improve_tke_diag/run4

Suite Information

Item	Value
Suite Name	main905c_improve_tke_diag/run4
Suite User	adrian.lock
Workflow Start	2026-05-07T16:29:19
Groups Run	all

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	MetOffice/jules@2026.03.2	True
lfric_apps	Adrian-Lock/lfric_apps@main905c_improve_tke_diag	False
lfric_core	MetOffice/lfric_core@3c8ccc6	True
moci	MetOffice/moci@2026.03.2	True
SimSys_Scripts	MetOffice/SimSys_Scripts@cab3315	True
socrates	MetOffice/socrates@2026.03.2	True
socrates-spectral	MetOffice/socrates-spectral@2026.03.2	True
ukca	MetOffice/ukca@1cdb9c2	True

Task Information

❌ failed tasks - 5

Task	State
check_lfric_atm_nwp_comorph_dev-C12_azspice_gnu_fast-debug-32bit-crun1	failed
check_lfric_atm_nwp_comorph_dev-C12_ex1a_cce_fast-debug-32bit-crun1	failed
check_lfric_atm_scm_comorph_dev_toga-BiP2x2-50000x50000_azspice_gnu_fast-debug-32bit	failed
check_lfric_atm_scm_comorph_dev_toga-BiP2x2-50000x50000_ex1a_cce_fast-debug-32bit	failed
validate_rose_meta	failed

✅ succeeded tasks - 1530

⌛ waiting tasks - 2

Task	State
housekeep_azspice	waiting
housekeep_ex1a	waiting

Test branch (from main with kgo updated) and update macro applied:

test2_improve_tke_diag

trac.log:

Test Suite Results - lfric_apps - test2_improve_tke_diag/run1

Suite Information

Item	Value
Suite Name	test2_improve_tke_diag/run1
Suite User	adrian.lock
Workflow Start	2026-05-08T13:11:05
Groups Run	all

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	MetOffice/jules@2026.03.2	True
lfric_apps	Adrian-Lock/lfric_apps@test2_improve_tke_diag	False
lfric_core	MetOffice/lfric_core@3c8ccc6	True
moci	MetOffice/moci@2026.03.2	True
SimSys_Scripts	MetOffice/SimSys_Scripts@cab3315	True
socrates	MetOffice/socrates@2026.03.2	True
socrates-spectral	MetOffice/socrates-spectral@2026.03.2	True
ukca	MetOffice/ukca@1cdb9c2	True

Task Information

✅ succeeded tasks - 1536

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

Needs to be added to the Boundary Layer documentation paper but will have to wait until it is ported. I've opened issue #490 to do this separately.

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

* As noted above, adding documentation for this change is pending the boundary-layer scheme doc being ported into lfric_apps (underway in PR #465) and will be addressed in a later PR.

(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

[James Bruten (james-bruten-mo)]

Hi Adrian, This Before Tag should be vn3.1 as the branch currently is (it might change when main is merged in).

[Adrian Lock (Adrian-Lock)]

Thanks James. Ah, I was thinking I would need to follow the revision in the lfric_atm/rose-app.conf, ie https://github.com/Adrian-Lock/lfric_apps/blob/main905c_improve_tke_diag/rose-stem/app/lfric_atm/rose-app.conf, but that's not the case then? This branch is made from main (at revision ...905c) because I didn't want major clashes with Ben's removal of j-loops.

[James Bruten (james-bruten-mo)]

No, it should use the latest AFTER_TAG of the versions.py file they're in, which in this case is still the latest release. This also means that if you were to add multiple macros in the same PR they might have different BEFORE_TAGs.

When apply_macros.py gets run it will copy this macro to places which use um-boundary_layer metadata and update the BEFORE_TAG to match the correct for that file.

[Adrian Lock (Adrian-Lock)]

OK, thanks, that makes sense and now fixed.

[James Bruten (james-bruten-mo)]

Cheers, macro looks good now

[MichaelWhitall]

Many thanks for this Adrian; I've looked through the branch and I think I've satisfied myself this is implementing exactly the same changes as the equivalent UM branch where I've copied the related code from the comorph_dev branch: https://github.com/MetOffice/um/compare/main...MichaelWhitall:um:vn14.1_improve_tke_diag
Just a couple of quick questions Re where I've spotted differences between the above UM branch and the changes here (I think there are good reasons but can I just check I've correctly understood the code?); see the in-line comments...

Cheers!
Mike

[MichaelWhitall]

That's great, thanks lots for clarifying; that's great you've been tidying-up and removing code for unused options! Sci/Tech review approved.

Cheers!
Mike

[Cameron Bateman (cameronbateman-mo)]

Hi Adrian, would it be possible to resolve the conflicts on the branch and ill start testing :), thanks. Adrian Lock (@Adrian-Lock)

[Adrian Lock (Adrian-Lock)]

No problem, conflicts merged. I've left the checksums as they were, because main has added a new namelist variable to the comorph_dev app and so those will need to be updated with the data from the merged branch. Is that something you can do?

[Cameron Bateman (cameronbateman-mo)]

Yes thank you for the resovling that. Yeah leave it with me thank you.