Correct the sample_physics_winds_correction option

[tommbendall]

PR Summary

Sci/Tech Reviewer: @atb1995
Code Reviewer: @allynt

The sample_physics_winds_correction option is broken (see Issue #66). This had not been detected as it is not currently covered by the test-suite.

This PR fixes this option and improves on the current situation by making the following changes:

• input fields to the w3_to_w2_correction_kernel are declared to depth 2: this kernel reads from a field with a depth 1 halo and is an INC kernel, so fields being read using stencils must be declared to depth 2 (they are only depth 1 by default)

• I have unified the sample_physics_winds_correction option with the other code to perform the sample_physics_winds: the sample_physics_winds_correction option should simply activate the correction routines, but it previously also changed the method of sampling

• it picks up a correction to the w3_to_w2_correction kernel from the Linked PR: Fix Correction to Sampling Physics Winds lfric_core#221

• I have turned this option on in an exoplanet rose-stem test to ensure that it is covered by the test-suite

• Linked to: Fix Correction to Sampling Physics Winds lfric_core#221

• Closes: The sample_physics_wind_correction option is broken #66

To demonstrate that this is working, I have created an artificial test in which a zonal wind component in W3 was specified to vary with latitude. This was then mapped to W2, with and without the correction option. The following plots show that grid imprinting on the meridional panel edges has been improved.

See the small divots on the meridional panel edges:

And zoomed in on a panel edge:

Code Quality Checklist

(Some checks are automatically carried out via the CI pipeline)

• I have performed a self-review of my own code
• My code follows the project's style guidelines
  style guidelines
• Comments have been included that aid undertanding and enhance the
  readability of the code
• My changes generate no new warnings

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 (eg. kgo changes)
• I have added tests to cover new functionality as appropriate (eg. system
  tests, unit tests, etc.)
• Any new tests have been assigned an appropriate amount of compute resource
  and have tests 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 - smp_phys_wind_correct/run1

Suite Information

Item	Value
Suite Name	smp_phys_wind_correct/run1
Suite User	thomas.bendall
Workflow Start	2026-01-15T15:18:33
Groups Run	developer', 'lfric_atm_extra

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@2025.12.1	True
lfric_apps	tommbendall/lfric_apps@TBendall/StochPhysFixes	False
lfric_core	tommbendall/lfric_core@TBendall/smp_phys_wind_correct	True
moci	MetOffice/moci@2025.12.1	True
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True
socrates	MetOffice/socrates@2025.12.1	True
socrates-spectral	MetOffice/socrates-spectral@2025.12.1	True
ukca	MetOffice/ukca@2025.12.1	True

Task Information

✅ succeeded tasks - 1256

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 (eg. PsyKAl-lite, Kernal
  inteface, optimisation scripts, LFRic data structure code) then please
  contact the
  tooscollabdevteam@metoffice.gov.uk

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

[atb1995]

This code fixes the current failure on main whilst using the sample_physics_winds_correction option - passing a field of the correct stencil depth and fixing the w3_to_w2_correction kernel in the linked PR by not using a vertical level index on a 2D field. Finally, it tidies/fixes the misused previous logic for application of the correction. I'm happy that the code is well written and does what was stated in the PR.

[tommbendall]

Thanks for the science review, @allynt this is now ready for code review