COSIMA TWG Meeting Minutes 2025

COSIMA TWG
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21

Date : 24 Sep 2025

Attendees: @sofarrell , @NoahDay , @dougiesquire , @ezhilsabareesh8 , @aekiss , @minghangli , @helen

Chair: @cbull
Minutes: @anton

CM3 Analysis - Chris

  • There is a CM3 analysis scoping meeting planned for in about 3 weeks. Check hive forum for the invite soon. Update: here’s relevant post.

OM3 Config Docs - Anton

  • We are going to move the all the documentation stubs back into main branch. The current stubs based system have incomplete versioning, are hard to edit and have weird quirks (like links breaking all the time)

  • Anton suggested CalVer versioning for the docs - when doing a config release, a docs release would be manually triggered at that time. (e.g. release-MC_25km_jra_ryf-1.0-beta would align with 2025.08.000 release)

  • Fixing docs is possible and increments the minor version only (e.g. 2025.08.001 is a future release, still related to release-MC_25km_jra_ryf-1.0-beta but with documentation only corrections)

  • In future, config and doc releases happen about the same time (e.g. release-MC_25km_jra_ryf-2.0-beta and 2026.0x.xxx docs)

Other business

  • Andrew Kiss thinks the bottom roughness calculation for OM3 inputs might be wrong. We need to change the length scale from one based on resolution to one based on the wavelength of the internal tides. AK will make an issue soon

  • Dougie - 100km branch sync. Dougie showed issue #771 and discussed doing a long-run soon, but EOS doesn’t impact this.

  • There is an OM2 build now with generic tracers based BGC. Should be able to use it with wombatlite, wombatmid, bling, cobalt etc. No config releases yet

  • Roster rotation happening next week

22

Date: 8 Oct 2025

Attendees: @sofarrell, @AndyHoggANU, @ezhilsabareesh8, @aekiss, @mmr0, @minghangli, @kieranricardo, @MartinDix, @helen
Chair: @cbull
Minutes: @dougiesquire

Sea-ice in OM3 runs

Kieran is curious whether we are seeing same issues in Northern Hemisphere as in CM3 (discussed in previous meeting I think)

No one has looked

Baltic sea salinity

Baltic sea is losing salt in CM3. Amount being lost is similar to the restoring applied in OM3.

Kieran: Shall we do some bulldozing?

Target is Baltic sea salinity stable around 8 or 9 g/kg

Ezhil will try deepening some of the particularly shallow cells

Ezhil also to update his OM3 salinity restoring comparison plots to compare to OM2 with “new” bathymetry

make_diag_table auxiliary variables

PR to add the option to include auxiliary fields with make_diag_table is here: Allow optional auxiliary_fields in each file by dougiesquire · Pull Request #14 · COSIMA/make_diag_table · GitHub

Upcoming releases?

25km RYF beta

Minghang is currently doing scaling tests to inform NCMAS proposals. Would be good to have a released version for this.

Agreed to do a minor release soon (1.1-beta)

100km alpha

Probably shouldn’t release without updating the grid

Won’t release anything soon

Panan alpha

No control run

Will target alpha release when this is in a configuration branch

NCMAS applications

Want to avoid multiple groups putting in applications that use ostensibly the same models and have wildly different compute costs.

Approximately 4 or 5 groups putting in NCMAS proposals.

Any information is needed within 10 days.

We’ll try to provide

  • Scaling info for:
    • MOM6 in Panan OM3 8km. Vary core counts for MOM only.
    • WW3 in OM3 100km. Vary core counts for WW3 only.
  • Cost for:
    • OM3 25km
    • OM3+WW3 100km
    • Panan OM3 8km

Still keen to hear from people about their plans for NCMAS. Trying to do the best we can with limited time

MOM baroclinic timestep

100km configs use MOM baroclinic timestep of 1800s and coupling/CICE timestep of 3600s. Increasing baroclinic timestep to 3600s causes MOM to crash. Should we spend time looking into increasing baroclinic timestep.

Decided that it was not a good use of time at this point.

Where to put observational products?

Where should one save observational datasets required for analysis notebooks (motivation is some sea-ice analysis to be done by Anton and friends + @aekiss has a MLD dataset that would be good to try and add).

Ping Josh on Zulip and ask: Log in | Zulip

23

Date: 22 Oct 2025
Attendees: @NoahDay, @sofarrell, @Paul.Gregory, @aekiss, @anton, @helen, @micael, @minghangli, @MartinDix, @ezhilsabareesh8
Chair: @cbull
Minutes: @dougiesquire

NCMAS applications

@micael gave overview of the software transformation team’s responsibilities. They will do scaling for models in conjunction with model dev teams. Will maintain repository of notebooks showing scaling studies.

Proposals require cost and scaling. Don’t need scaling for every configuration. In previous years applicants have shared around tables of the cost for each model. Usually this information exists from previous runs people have done.

Can we have a coordinated dissemination of the information to the community?

@micael will share draft of a Forum post on model scaling notebooks tomorrow. @minghangli and @ezhilsabareesh8 will review/give input.

Use normal queue for postprocessing

@dougiesquire will update the configs to use normal queue rather than express for collation and postscript jobs.

Workflow docs meeting for access hive

Chris is meeting @paigem tomorrow to talk access hive workflow docs (e.g. how to run payu, publish an experiment etc) get in touch if you have ideas/want to join.

Cm3 dev team minutes are moving to a more open format

See new announce page and @MartinDix will be posting minutes. ACCESS CM3 technical meeting minutes

Residual sea ice

There is an upstream PR to CICE to zap residual sea ice (non-physical regions of trapped low concentration ice). @anton has done test runs with this on in ACCESS-OM3 see here.

Investigation is still ongoing - see the above linked PR.

Run logs

We should be pushing run logs for experiments we run. Should we have a shared repo, a la ACCESS-ESM1.6?

@cbull will set up a repo in the ACCESS-Community org and will ping those that have run experiments

Compute allocations

@cbull showed what has been used in tm70 so far this quarter.

ACCESS-NRI is planning to ask an additional 5MSU for Q1,2-2026. Storage will remain the same.

CM3 drop in hackathon

Tomorrow at 1pm. Details here.

Updating OM3 initial conditions

@dougiesquire will update initial conditions to include potential temp, conservative temp, practical salt and absolute salt.

This makes it easier to set up the correct initial conditions and restoring for a given model configuration. Also, facilitates evaluation.

@dougiesquire will also look into reconciling the duplicate downloads of WOA23 in ik11 and av17.

New IAF run

@aekiss and @ezhilsabareesh8 probably need to do a few more test runs for bathymetry edits (Bosphorous,…). These will be prototype runs, just to check edits are having desired effect.

@aekiss possibly also worth looking at a few more diagnostics in the existing IAF run.

We want to have a release before doing another long run.

@cbull will open an issue for listing changes we want to make before an IAF release and others can contribute what they would like to see in the new run.

CM3 team will be interested in picking up the released version.