Inland basin flow coupling

[Dan Copsey (DanCopsey)]

PR Summary

Sci/Tech Reviewer: Maggie (@maggiehendry)
Code Reviewer: Erica Neininger (@ericaneininger)

Receive inland basin flow from the rivers executable via OASIS and transfer that water into JULES to end up in the soil.

• linked MetOffice/jules#89
• linked MetOffice/um#63

• closes Inland basin flow coupling #234

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_inland_flow/run5

Suite Information

Item	Value
Suite Name	lfric_test_inland_flow/run5
Suite User	dan.copsey
Workflow Start	2026-04-02T16:10:37
Groups Run	developer

Dependency	Reference	Main Like
casim	MetOffice/casim@2026.03.2	True
jules	DanCopsey/jules@inland_flow	True
lfric_apps	DanCopsey/lfric_apps@test_inland_flow_v5	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

[Dan Copsey (DanCopsey)]

Currently run_lfric_coupled_nwp_gal9-C48_ex1a_cce_fast-debug-64bit fails with:
ERROR: soil_moisture has gone negative with a value of -0.28421709E-13
I will investigate.

[Maggie (maggiehendry)]

I'm on leave currently. I'll need to review when I return on 23rd April.

[Maggie (maggiehendry)]

Currently run_lfric_coupled_nwp_gal9-C48_ex1a_cce_fast-debug-64bit fails with: ERROR: soil_moisture has gone negative with a value of -0.28421709E-13 I will investigate.

Did you get to the bottom of this Dan Copsey (@DanCopsey)?

[Dan Copsey (DanCopsey)]

Currently run_lfric_coupled_nwp_gal9-C48_ex1a_cce_fast-debug-64bit fails with: ERROR: soil_moisture has gone negative with a value of -0.28421709E-13 I will investigate.

Did you get to the bottom of this Dan Copsey (Dan Copsey (@DanCopsey))?

I did get to the bottom of it and fixed it. The problem was inland_outflow_rp (and rivers_outflow_rp) was not being initialised to zero (but being initialised to rmdi instead). I fixed it with this change:

https://github.com/MetOffice/jules/commit/a2f80cb9342dddcb464c1909344b6ca5d74626de

If it is a coupled model then it makes it a requirement that these fields are initialised to something (using add_to_list). If they are not sent to add_to_list then they will be initialised with rmdi (so I have corrected the warning message which was issuing the wrong warning).

[James Bruten (james-bruten-mo)]

Macro looks good

[Dan Copsey (DanCopsey)]

This code change still changes results in the coupled model even when inland basin flow coupling is turned off as it also includes a bug fix which is the multiplying of runoff by flandg (land fraction) in jules_extra_kernel_mod.F90. I have updated the KGOs in this chanegset:
fd97d92

I think my work here is done. Passing back to Maggie for Sci/tech review.

[Maggie (maggiehendry)]

I'm just about finished with your tickets. Just one query in the LFRic apps changes.

[Maggie (maggiehendry)]

Do the changes to the checksums need reverting?

[Dan Copsey (DanCopsey)]

Hi Maggie (@maggiehendry) . The change to the checksums is still needed as there was a bug in the runoff that this branch also fixes. The runoff should be multiplied by the land fraction in order to conserve water. This changes results. See lines 1058 to 1061 of jules_extra_kernel_mod.F90:

https://github.com/MetOffice/lfric_apps/pull/401/changes#diff-f403c1009c2f45aa4edc90a08257ea92cdb90eb7a9b0df7bedd9b8ec91ea3ebf

I will also add this to the ticket description.

Dan.

[Maggie (maggiehendry)]

Oh yes. I remembering seeing the runoff multiplied by land fraction. Thanks.

[Maggie (maggiehendry)]

Thanks Dan Copsey (@DanCopsey). This is now good to go 😄.

[James Bruten (james-bruten-mo)]

Hi Dan Copsey (@DanCopsey)
My PRs #463 and MetOffice/Jules#110 have just been merged which will cause clashes with this. lfric-jules_shared and lfric-jules metadata sections now exist in the Jules repo. The metadata duplication is no longer needed here, so the incoming deletion to jules-hydrology can just be accepted. The incoming deletion of the jules-lfric versions.py file can also be accepted, but the added upgrade macro should be moved to jules-lsm instead.
You shouldn't need any changes on the jules/UM PRs.

[Dan Copsey (DanCopsey)]

Hi James Bruten (@james-bruten-mo) ,
I have updated my LFRic and JULES branches to HOT by merging in main. I moved across the upgrade macro to jules-lsm as you suggested. I then tried running the lfric_coupled rose-stem test to make sure I hadn't broken anything and I had a couple of issues which were easy to resolve. Now the rose-stem test passes and I think you can carry on with your code review.
Thanks,
Dan.