PR Summary

Sci/Tech Reviewer: @P-Burns
Code Reviewer:

The boundary_layer code imported to lfric_apps from the UM contained a number of old options that are no longer used and are not even available in lfric_apps. Here, I'm taking this opportunity to remove 3 of these switches (l_lambdam2, l_full_lambdas and var_diags_opt). This then also permits a more logical reorganisation of the code in ex_coef that should make it easier to read and also to modify further in the future. Scientifically there are no changes at all and the KGO are preserved.
Note that I did also try removing a 4th hardwired switch, l_use_var_fixes, but so-doing broke KGO (for just the
coupled_nwp_gal9_64bit app, presumably due to some interaction with the compiler optimisation in the subroutine excf_nl.F90) so I've have reverted that change in the latest revision. Subject to discussion with reviewers.

Update 21/01/2026: following discussions with the Sci-tech reviewer, I've now removed the redundant variable h_blend_orog all through the LFRic code tree (it was being passed from JULES but always containing zeros as the effective orographic roughness scheme is not available in LFRic, and has been superseded by the distributed version in all configurations). All developer tests still maintain kgo, see updated trac.log below.

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): no changes to kgo
• I have added tests to cover new functionality as appropriate (eg. system
  tests, unit tests, etc.): no new functionality added
• 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): no new tests added or needed

trac.log

Test Suite Results - lfric_apps - ex_coef_tidy/run4

Suite Information

Task Information

✅ succeeded tasks - 1106

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

• None 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: no changes needed

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