Lfric2lfric: interpolate W2 fields

[ukmo-juan-castillo]

PR Summary

Sci/Tech Reviewer: @mike-hobson
Code Reviewer: @TeranIvy

This is relatively simple change to allow lfric2lfric to regrid W2 fields. The accepted procedure to deal with W2 is to convert them to a set of two W3 and one Wtheta fields, process these fields, and then regenerate back a W2 field with the resulting W3 and Wtheta fields.

This changes will make use of the existing subroutines converting W2 to W3,Wtheta fields, and back.

• closes lfric2lfric: processing W2 fields #60
• fixes lfric2lfric: processing W2 fields #60

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)

No new tests were deemed necessary. The changes will necessary change KGOs, because now W2 fields will be processed, but no changes are expected in other fields.

trac.log

Test Suite Results - lfric_apps - lfric2lfric_W2/run3

Suite Information

Item	Value
Suite Name	lfric2lfric_W2/run3
Suite User	juan.m.castillo
Workflow Start	2026-02-12T16:57:04
Groups Run	all

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@69aaf4d	True
lfric_apps	ukmo-juan-castillo/lfric_apps@lfric2lfric_W2	False
lfric_core	MetOffice/lfric_core@bbb3d8a	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 - 1461

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