Fix Correction to Sampling Physics Winds

[tommbendall]

PR Summary

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

This is a simple fix to the sci_w3_to_w2_correction kernel, to ensure that the 2D displacement field is indexed correctly (it is currently indexed as a 3D field when it is not).

This is linked to MetOffice/lfric_apps#69, which fixes other bugs with the sample_physics_winds_correction option.

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
• Comments have been included that aid understanding and enhance the
  readability of the code
• My changes generate no new warnings

Testing

• I have tested this change locally, using the LFRic Core rose-stem suite
• If required (e.g. API changes) I have also run the LFRic Apps test suite
  using this branch
• 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_core - core_smp_phys_wind_correct/run1

Suite Information

Item	Value
Suite Name	core_smp_phys_wind_correct/run1
Suite User	thomas.bendall
Workflow Start	2026-01-15T15:21:44
Groups Run	developer

Dependency	Reference	Main Like
lfric_core	tommbendall/lfric_core@TBendall/smp_phys_wind_correct	False
SimSys_Scripts	MetOffice/SimSys_Scripts@2025.12.1	True

Task Information

✅ succeeded tasks - 372

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
  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]

Code looks good, approved

[tommbendall]

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