Add zenith angle to sea ice albedo calculations

[Dan Copsey (DanCopsey)]

PR Summary

Sci/Tech Reviewer: John Edwards (@JMEdwardsXtr)
Code Reviewer: Erica Neininger (@ericaneininger)

Adds a zenith angle dependence to the calculation of albedo for bare sea ice, snow on sea ice and melt ponds. See issue #88 for more details.

• linked MetOffice/um#136
• linked Add zenith angle dependence to sea ice albedo calculations lfric_apps#438

• closes Add zenith angle dependence to sea ice albedo calculations #88

Code Quality Checklist

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

• [x ] I have performed a self-review of my own code
• [x ] My code follows the project's style guidelines
• [x ] Comments have been included that aid understanding and enhance the readability of the code
• [x ] My changes generate no new warnings
• If editing rose-meta/jules-shared then have you supplied a linked UM and LFRic Apps PR?

Testing

• [x ] I have tested this change locally, using the JULES rose-stem suite
• If shared files have been modified, I have run the UM and LFRic Apps rose stem suites
• 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.)

trac.log

Test Suite Results - jules - jules_zenith_angle_seaice/run4

Suite Information

Item	Value
Suite Name	jules_zenith_angle_seaice/run4
Suite User	dan.copsey
Workflow Start	2026-08-28T17:17:50
Groups Run	all

Dependency	Reference	Main Like
jules	dancopsey/jules@zenith_angle_seaice	False
SimSys_Scripts	MetOffice/SimSys_Scripts@2026.07.1	True

Task Information

❌ failed tasks - 1

Task	State
nccmp_meto_ex1a_gfortran_imogen_layeredc_ch4	failed

✅ succeeded tasks - 673

⌛ waiting tasks - 1

Task	State
housekeep_meto_ex1a_gfortran_imogen_layeredc_spinup	waiting

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

Approvals

Please request all relevant approvals. See the CodeOwners.txt file for section owners.

Technical

• JULES Code Owner
• OpenMP
• River Routing
• Rose Stem
• Rose Metadata
• Upgrade Macros

Scientific

• Surface
• Hydrology
• Vegetation
• Veg3 RED Demography
• Biogeochemistry
• Biogenic fluxes
• Fire
• Lakes
• Evaluation
• Imogen

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

[github-actions]

⚠️ Hello Dan Copsey (@DanCopsey)!

Your CLA signature was found on the base branch, but you appear to have modified the CONTRIBUTORS.md file in this PR.

Please do not edit the CONTRIBUTORS.md file. If you have already signed the CLA, revert changes to the file and your signature will be picked up.