#81: Fix unallocated arrays in ukca_volcanic_so2

[mcdalvi]

PR Summary

Sci/Tech Reviewer: @alanjhewitt
Code Reviewer: @oakleybrunt

Arrays true_latitude, true_longitude and weight_volc_vertdist are being used without being allocated in LFRic copy of ukca_volcanic_so2 routine. This might have been a fallout of migrating the UM physics code.
This is causing CCE builds on ARCHER2 to fail, and warnings during the GNU compilation.

Note: the Volcanic_SO2 emission functionality is not yet fully linked up in LFRic. Hence this PR will also add a check to ensure that the routine is not called.

Issue: #81

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 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.)
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trac.log

Test Suite Results - lfric_apps - fix_i81_ukca_volc/run2

Suite Information

Item	Value
Suite Name	fix_i81_ukca_volc/run2
Suite User	mohit.dalvi
Workflow Start	2026-01-19T09:59:37
Groups Run	developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2025.12.1	True
jules	MetOffice/jules@2025.12.1	True
lfric_apps	mcdalvi/lfric_apps@fix_i81_ukca_volc	False
lfric_core	MetOffice/lfric_core@5d4d72f	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 - 1106

Testing information from ARCHER2 is noted in the issue:81 Summary

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
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• 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

[jennyhickson]

Hi Mohit. Just assigning a code reviewer for you and noticed that this pull request is asking to merge changes into "Stable". You'll need to change that to "Main". This is done right a the top, just under the title of the PR. Thanks

[mcdalvi]

Testing passed - ready for Sci-tech Review @alanjhewitt

[alanjhewitt]

Hi Mohit,

Thanks for making this change.

I think the clean error message could be clearer why its not working, because the next person to see this message will likely be a scientist rather than a software engineer, and we want to make it easy for them to figure out what is wrong.

Keep it brief but say that it needs to be implemented before the code will work.

Alan

[alanjhewitt]

Could you change the error message, so that it says the functionality is not yet developed/implemented for lfric.

[mcdalvi]

Error message updated for clarity - 49a8a2d
Test suite is still running, but most tasks (especially build ones) have passed so no syntax errors in the change.
Passing back to @alanjhewitt

[alanjhewitt]

Thanks Mohit, looks good. Approved