Add zenith angle dependence to sea ice albedo calculations

[Dan Copsey (DanCopsey)]

PR Summary

Sci/Tech Reviewer:
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 #400 for more details.

• linked Add zenith angle to sea ice albedo calculations jules#104

• closes Add zenith angle dependence to sea ice albedo calculations #400

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)

trac.log

Test Suite Results - lfric_apps - lfric_test_zenith_angle_seaice/run1

Suite Information

Item	Value
Suite Name	lfric_test_zenith_angle_seaice/run1
Suite User	dan.copsey
Workflow Start	2026-04-10T16:14:47
Groups Run	developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	DanCopsey/jules@zenith_angle_seaice	True
lfric_apps	DanCopsey/lfric_apps@zenith_angle_seaice	False
lfric_core	MetOffice/lfric_core@018e40c	True
moci	MetOffice/moci@2026.03.2	True
SimSys_Scripts	MetOffice/SimSys_Scripts@4387949	True
socrates	MetOffice/socrates@2026.03.2	True
socrates-spectral	MetOffice/socrates-spectral@2026.03.2	True
ukca	MetOffice/ukca@2026.03.2	True

Task Information

✅ succeeded tasks - 1165

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

[James Bruten (james-bruten-mo)]

The upgrade macro looks fine, but you've got a new .versions file which should be deleted. It probably came during an aborted run of apply_macros.py

[iboutle]

I would suggest setting !kind=double here and for the other 2 real-valued inputs - we are going to pass these values direct to jules at double precision (r_um), hence it makes sense to read them in at double precision (rather than the default which is usually single now)

[Dan Copsey (DanCopsey)]

Without the new code the coupled app took 261 seconds.
With the new code (and turned on) the coupled app took 257 seconds.
Therefore this new code does not affect runtime.

[Maggie (maggiehendry)]

Can these metadata changes please be moved to:

interfaces/jules_interface/rose-meta/lfric-jules-shared/jules-sea-seaice/HEAD/rose-meta.conf

Thanks.

[Maggie (maggiehendry)]

Can you please run rose config-dump -C interfaces/jules_interface/rose-meta/lfric-jules-shared/jules-sea-seaice/HEAD/ thanks.

[Maggie (maggiehendry)]

I realise now that this group of tickets has not been passed into review yet as the UM branch doesn't have a PR yet. Perhaps this should be a draft still? I can't give approval until all repos are submitted.

[Maggie (maggiehendry)]

Suggested change

ns=namelist/Science/JULES Surface/Sea and sea-ice

All the lines ns=namelist/Science/JULES Surface/Sea and sea-ice need deleting as the panels have been reorganised for JULES Science Settings

[James Bruten (james-bruten-mo)]

[Bulk Update]

This has been removed from the Summer 2026 milestone as the review deadline has now passed. Please contact the SSD team if you think this was in error.