Refactor wet model drivers and controllers

[Pierre Siddall (Pierre-siddall)]

PR Summary

Code Reviewer: Erica Neininger (@ericaneininger)

This PR migrates over the ticket number 523 from subversion which was authored by Harry Shepherd (@harry-shepherd) and contained the following description:

As part of the first priority items for the drivers refactor, there is extensive work to do on the wet model drivers and controllers. For this context I take these to be:

• NEMO
• TOP (Medusa)
• SI^3

As all of these have similar functionality, and areas of code that work in the same way. The original design brief for the drivers was to ensure orthogonality between components, and this will still be followed to allow the SI^3^ controller to easily be reconfigured into a driver if that is desired. However code reuse will be made use of as much as possible (which was not the case in the original implementation of the controllers).

As CICE is not part of GC5, refactoring of that driver is a 2nd tier priority item.

Work in this ticket includes (but is not limited to):
NEMO

• Splitting up {{{setup_executable}}} into discrete tasks that can be unit tested
• Splitting up {{{finalize_executable}}} in a similar way
• Unit testing other functions

SI^3 and Top
The controllers will be removed

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
• 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 Moci rose-stem suite
• 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.)

Test Suite Results - moci - test-refactor-wet-model/run2

Suite Information

Item	Value
Suite Name	test-refactor-wet-model/run2
Suite User	pierre.siddall
Workflow Start	2026-06-03T08:21:17
Groups Run	all

Dependency	Reference	Main Like
moci	Pierre-siddall/moci@refactor-wet-model	False
SimSys_Scripts	MetOffice/SimSys_Scripts@main	True

Task Information

✅ succeeded tasks - 120

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

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

[Erica Neininger (ericaneininger)]

• I believe some of the functionality added since the original SRS branch was committed has been lost - particularly anything that was removed from nemo_driver.py into new files. The branch was cut a r4173. There are (at least) two diffs which should be considered:

1. https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5833%40main%2Ftrunk%2FCoupled_Drivers&old=4161%40main%2Ftrunk%2FCoupled_Drivers
2. https://github.com/MetOffice/moci/commits/main/Coupled_Drivers/nemo_driver.py

I may not have picked up on all the specifics here - this may be an iterative review process!

• Since this affects all UM jobs using the drivers, Can you please run the UM rose-stem "coupled" group with this branch added to the dependencies.yaml file?

• Copyright notice - Please replace all headers in modified files with the updated Momentum Copyright notice. New files obviously get the new one as well please.

[Erica Neininger (ericaneininger)]

Please include modifications made under SRS tickets #605 & 667, to nemo_driver.py between lines 333-339 (original) and lines 343-351 (updated)
https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5562%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py&old=4876%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py

[Erica Neininger (ericaneininger)]

I think that restart_icebergs here is now variable - it may alternatively be restart_icb?? depending on NEMO version.

Please see changes made under SRS tickets #605 & #667 in nemo_driver.py beginning around line 410 in the modified file.
https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5562%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py&old=4876%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py

[Erica Neininger (ericaneininger)]

I think that, depending on NEMO version, the namelist variable may alternatively be rn_dt.

Please see changes made under SRS tickets #605 & #667, in nemo_driver.py beginning around line 410.
https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5562%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py&old=4876%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py

[Erica Neininger (ericaneininger)]

        Restarts('Icebergs', '%so_icebergs_%s_restart', 'restart_icebergs'),

The NEMO restart file for icebergs changed at NEMO4 to better match all the others -
So depending on version, I think this call to Restarts might alternatively need to be (I think!)

        Restarts('Icebergs', '%so_$s_restart_icb', 'restart_icb'),

Please see changes made in SRS tickets #605 & #667 in nemo_driver.py around line 537.
https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5562%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py&old=4876%40main%2Ftrunk%2FCoupled_Drivers%2Fnemo_driver.py

[Erica Neininger (ericaneininger)]

• I believe some of the functionality added since the original SRS branch was committed has been lost - particularly anything that was removed from nemo_driver.py into new files. The branch was cut a r4173. There are (at least) two diffs which should be considered:

1. https://code.metoffice.gov.uk/trac/moci/changeset?reponame=&new=5833%40main%2Ftrunk%2FCoupled_Drivers&old=4161%40main%2Ftrunk%2FCoupled_Drivers
2. https://github.com/MetOffice/moci/commits/main/Coupled_Drivers/nemo_driver.py

I may not have picked up on all the specifics here - this may be an iterative review process!

• Since this affects all UM jobs using the drivers, Can you please run the UM rose-stem "coupled" group with this branch added to the dependencies.yaml file?

• Copyright notice - Please replace all headers in modified files with the updated Momentum Copyright notice. New files obviously get the new one as well please.