Lfric2lfric vertical regridding infrastructure

[cjohnson-pi]

PR Summary

Add the infrastructure required for both horizontal and vertical regridding.

At the moment lfric2lfric can do horizontal regridding. Additional meshes, vertical extrusions, and chi fields (with appropriate orography) are required to enable vertical regridding.

Sci/Tech Reviewer: Lottie Turner (@mo-lottieturner)
Code Reviewer: Ed Hone (@EdHone)

• blocks Different number of tiles in source and target for lfric2lfric #685
  is related to vertical regridding kernels Vertical regridding in lfric2lfric #253

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 - lfric2lfric_extrusions/run27

Suite Information

Item	Value
Suite Name	lfric2lfric_extrusions/run27
Suite User	christine.johnson
Workflow Start	2026-07-16T13:13:24
Groups Run	suite_default

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.07.1	True
jules	MetOffice/jules@2026.07.1	True
lfric_apps	cjohnson-pi/lfric_apps@lfric2lfric_extrusions	False
lfric_core	MetOffice/lfric_core@2026.07.1	True
moci	MetOffice/moci@2026.07.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2026.07.1	True
socrates	MetOffice/socrates@2026.07.1	True
socrates-spectral	MetOffice/socrates-spectral@2026.07.1	True
ukca	MetOffice/ukca@2026.07.1	True

Task Information

❌ failed tasks - 5

Task	State
check_lfric2lfric_oasis_C12L70_to_C12L38_azspice_gnu_fast-debug-64bit	failed
check_lfric2lfric_oasis_C12L70_to_C12L38_ex1a_cce_fast-debug-64bit	failed
check_lfric2lfric_oasis_C12L70_to_seukL38_azspice_gnu_fast-debug-64bit	failed
check_lfric2lfric_oasis_C12L70_to_seukL38_ex1a_cce_fast-debug-64bit	failed
kgo_groups_checker	failed

✅ succeeded tasks - 1214

⌛ 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

[David Lee (davelee2804)]

Hi cjohnson-pi , thank you very much for looping my in here. Unfortunately we can't build lfric2lfric at the moment as we don't yet have a software container for PSyclone vn3.3.1 - so sadly I cannot test the branch :(. I suggest removing me from the list of reviewers. Again, really sorry I can't be of any help here, hopefully we'll have our updated container up and running soon....

[cjohnson-pi]

Hi cjohnson-pi , thank you very much for looping my in here. Unfortunately we can't build lfric2lfric at the moment as we don't yet have a software container for PSyclone vn3.3.1 - so sadly I cannot test the branch :(. I suggest removing me from the list of reviewers. Again, really sorry I can't be of any help here, hopefully we'll have our updated container up and running soon....

I think this branch must have changed some code that you are code owner for as github had in fact added you as a reviewer automatically. I'm not sure how to remove you from the list (if anyone knows, please tell me!). At the moment, the protocol for code owners seems to be that github automatically adds you as a reviewer but this doesn't mean you have to do a review. Its just notifying you of work thats going on and if youd like to make some comments you can. I think its just science reviewer and code reviewer that have to do reviews.

[David Lee (davelee2804)]

Hi cjohnson-pi , as commented, would you be able to add these lines to:
https://github.com/MetOffice/lfric_apps/blob/main/rose-stem/site/nci/groups/groups_lfric2lfric.cylc#L16
so that we can run these tests at nci via our CI testing pipeline?

[David Lee (davelee2804)]

Hi cjohnson-pi , would it be possible to add these tests to the nci Rose stem tests as well? Specifically adding the lines:

"lfric2lfric_oasis_C12L70_to_seukL38_gadi_intel_fast-debug-64bit",
"lfric2lfric_oasis_C12L70_to_C12L38_gadi_intel_fast-debug-64bit",

to:
https://github.com/MetOffice/lfric_apps/blob/main/rose-stem/site/nci/groups/groups_lfric2lfric.cylc#L16
?

That way we can keep up to date with the Rose stem test coverage as well.

[cjohnson-pi]

Done. Thanks.

[David Lee (davelee2804)]

Thanks very much for adding the nci Rose stem tests cjohnson-pi ! much appreciated...

[Lottie Turner (mo-lottieturner)]

This all looks good to me. I have a small query about what order this is going on vs the vertical regridding kernels, as this adds testing that makes use of those kernels so should presumably be going on after that ticket? If so you should add - blocked by: #253 to the summary.

A question about the diagram at the top - should the higher-res orography come in directly after the horizontal regrid? rather than being in the same step as the vertical regrid

[cjohnson-pi]

This all looks good to me. I have a small query about what order this is going on vs the vertical regridding kernels, as this adds testing that makes use of those kernels so should presumably be going on after that ticket? If so you should add - blocked by: #253 to the summary.

A question about the diagram at the top - should the higher-res orography come in directly after the horizontal regrid? rather than being in the same step as the vertical regrid

The intermediate grid needs to use the interpolated low-res orography. This is the same as the UM See https://github.com/MetOffice/um/blob/main/src/utility/qxreconf/rcf_interpolate_mod.F90#L233 where the middle grid heights are derived using interp_orog. The interpolation of the low-res orography in lfric2lfric is already on trunk.

Regarding the ordering of the tickets, this ticket is not blocking #253. Both tickets can be merged on independently. And then a follow on ticket will be created to add the call the vertical interpolation kernels and test in a real scenario.