Add custom CMOR table and derivation script for permafrost

[axel-lauer]

Description

This PR adds (a) custom CMOR tables for the following three ESACCI-PERMAFROST variables:

• active layer thickness (alt)
• permafrost ground temperature (gtd)
• permafrost extent (pfr)

and (b) a derivation script for permafrost extent (pfr) to calculate this variable from the CMIP models.

Checklist

It is the responsibility of the author to make sure the pull request is ready to review. The icons indicate whether the item will be subject to the 🛠 Technical or 🧪 Scientific review.

• 🧪 The new functionality is relevant and scientifically sound
• 🛠 This pull request has a descriptive title and labels
• 🛠 Code is written according to the code quality guidelines
  - [ ] 🧪 and 🛠 Documentation is available
• 🛠 Unit tests have been added
• 🛠 Changes are backward compatible
  - [ ] 🛠 Any changed dependencies have been added or removed correctly
  - [ ] 🛠 The list of authors is up to date
• 🛠 All checks below this pull request were successful

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.61%. Comparing base (9244717) to head (c5453bb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2358      +/-   ##
==========================================
+ Coverage   95.59%   95.61%   +0.01%     
==========================================
  Files         266      267       +1     
  Lines       15573    15629      +56     
==========================================
+ Hits        14887    14943      +56     
  Misses        686      686              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

In order to maintain a backlog of relevant pull requests, we automatically label them as stale after 180 days of inactivity.

If this pull request is still important to you, please comment below to remove the stale label. Otherwise, this pull request will be automatically closed in 60 days. If this pull request only suffers from a lack of reviewers, please tag the @ESMValGroup/technical-lead-development-team so they can help you find a suitable reviewer.

[bouweandela]

It looks like there is also a derivation function in this pull request that is not mentioned in the description at the top. Is that intentional? If yes, please make sure that the derivation is lazy and add a unit test for it.

[bouweandela]

If you click the Update branch button or run git pull origin main --no-ff and git push locally, the tests on CircleCI should run again.

[schlunma]

Hello, this pull request has been marked with the v2.14.0 milestone. The release of version 2.14.0 is currently scheduled for February 2026. To get this into the new release, it would be great to get this merged by the end of January.

If you won't be able to finish this in time, don't worry - just unassign the milestone v2.14.0. If you need any support, ping myself (@schlunma; the release manager for v2.14.0) or the @ESMValGroup/technical-lead-development-team. Please note that I won't be available until the beginning of February, though.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.50%. Comparing base (539fe90) to head (75c7398).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2358   +/-   ##
=======================================
  Coverage   96.49%   96.50%           
=======================================
  Files         280      281    +1     
  Lines       16282    16348   +66     
=======================================
+ Hits        15711    15776   +65     
- Misses        571      572    +1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[schlunma]

Sorry, it looks like we cannot reach a consensus on this in time for v2.14.0. Moving this to v2.15.0, please let me know if this causes any troubles.

[rbeucher]

Hi all, as we prepare for the ESMValCore v2.15.0 release, the planned code freeze is 19 June 2026.

This PR is currently marked for the v2.15.0 milestone. Could you please confirm whether it should remain in scope for this release, or whether it would be better moved to a later milestone?

@flicj191 tagging you for release-freeze awareness.

[flicj191]

Hi all, sorry this couldn't be completed for 2.15, I will move this to 2.16. Let me know any issues.

[axel-lauer]

I think all comments are now addressed and this PR would be ready for merging.

[bouweandela]

Could you take a look at the output of pre-commit run -a please? There appear to be a few formatting and spelling issues. Technically, this looks good to me now, but it would need a scientific review as the algorithm is non-trivial.

[axel-lauer]

Thanks @bouweandela ! I fixed the issues found by pre-commit here: 3ea1cbd

@LisaBock it would be fantastic if you could do a scientific review...

[axel-lauer]

@LisaBock Just in case, here is a recipe that could be used for testing: https://github.com/ESMValGroup/ESMValTool/blob/cmug_test_recipes/esmvaltool/recipes/esa/recipe_pfr_test.yml

[LisaBock]

Thanks @axel-lauer ! The run with the test recipe was successful and the results looks fine to me.

[schlunma]

Thanks all!