COSIMA TWG Meeting Minutes 2023

Summary of my notes from the COSIMA TWG meeting today. Please add whatever I’ve missed/misrepresented (this is a wiki post so can be directly edited, or add a comment below to expand or add additional points to topics that were raised)

Date : 2023-02-08
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Angus Gibson @angus-g, Harshula Jayasuriya @harshula, Aidan Heerdegen @Aidan, Siobhan O’Farrell @sofarrell


  • Restating of previous discussions. Choice between permissive and not-permissive has been made. Definitely want permissive. Now choice is between a license that requires changes to be contributed back when code is redistributed vs one where this is not required.
  • Decided need to provide these two choices and some contextual information, pros/cons etc, to main community to make decision. @micael agreed to start a topic outlining this information.


  • JRA55-do will stop being updated at the end of January 2024. Groups such as GFDL are looking to develop an ocean driving product based on ERA5. Potentially makes the work to integrate ERA5 forcing into ACCESS-OM2 even more important:
    – ACCESS-OM2 will no longer be able to be run with up to date forcing product to investigate recent events of scientific and/or societal importance
    – ACCESS-OM3 is less well characterised/understood, which makes evaluating a forcing product more difficult. Comparing both products in ACCESS-OM2 makes it easier to assess differences between them, informing OM3 work.

Update on ACCESS-OM3 source build

  • All components now building using CMake. Except the driver, not yet done. Was going to write one, then saw a generic driver was available, ESMx, will investigate using this.

MPI libraries on Gadi

  • @micael did some benchmarks using the Octopus code, which has some similarities with MOM6 (it solves time-dependent differential equations on a grid using finite-differences). He sees that Intel MPI is slower than OpenMPI for communication (as expected) but faster for the memory and CPU bound parts of the code (somehow surprising). Despite slower communication, this leads to faster overall times for one specific case, using ~1000 cores. For profiling of MOM6, we should make sure to test both libraries.

Update on progress with ACCESS-OM2 spack build

  • @harshula gave a short overview of what is needed to make a spack package file, which is required to build a software project with spack. Illustrated this with two examples: libaccessom2 which has a complete and well configured build system, and oasis3-mct which does not.
  • Entire ACCESS-OM2 build completes automatically in a few minutes on his laptop with gcc compiler.

Not quite: communications are slower with Intel MPI, but the CPU and memory bound parts of the code (i.e., the ones that don’t perform any communications) are faster.

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Please edit the post to reflect what you said @micael.

I think it is better to make the “minutes” as accurate as possible, rather than require readers to look at all the comments to get the full picture. Doesn’t mean you have to delete the comment, it is useful to know there was a problem that was updated.

Thanks for the correction, I must’ve misunderstood you. That seems even weirder than I thought!

Summary of my notes from the COSIMA TWG meeting today. Please add whatever I’ve missed/misrepresented (this is a wiki post so can be directly edited, or add a comment below to expand or add additional points to topics that were raised)

Date : 2023-03-08
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Aidan Heerdegen @Aidan, Siobhan O’Farrell @sofarrell, Andy Hogg @AndyHoggANU, Adele Morrison @adele157, Kieran Ricardo @kieranricardo, Paul Leopardi @paulleopardi, Matt Chamberlain @matthew.chamberlain, Martin Dix @MartinDix, Dougie Squire @dougiesquire

MOM6-SIS2 scaling

@micael described scaling tests of regional pan-antarctic simulation

  • Scaling tests show how many cores it is possible to use while not wasting too many resources. Runs tried to stay close to real production runs, so that the time spent in Init and finalise is realistic
  • Ocean component scales better than the ice component and the atmospheric forcing. Not an issue as most time is spent in the ocean part.
  • Might be worth changing the IO layout to improve IO performance.
  • Rui Yang performed a more detailed analysis of what is happening in the code during one run (10th deg. with 962 cores). Main findings:
    • High MPI overhead: a lot of waiting due to load imbalance. This seems to come from the open-boundaries
    • Little vectorisation


  • Is boundary forcing read in every timestep? Files are daily, not sure if they are being read in once for a day
  • Maybe optimise layout
  • Could try testing global 0.1 scaling and see what difference boundaries make
  • Could ask for advice on a MOM6 forum
  • Could we make boundary cells smaller, give them less work to do, or change affinity and assign more CPUs
  • Compressed and chunked in time? Angus made sure chunk size is 1 in time


  • A lot depends on CMIP7 post meeting
  • Interest in ACCESS-CM3 and ACCESS-ESM3 based on ACCESS-OM3. Tight timelines for IPCC reporting. Spin-up is time consuming. Hard to do in parallel and hit deadlines.
  • Possible is two-pronged approach, above and a fallback approach adding ESM components to CM2
  • No progress on decision yet. @AndyHoggANU working on notes to get out to people to get a decision. Chicken-egg problem
  • COSIMA can benefit from ACCESS-CM3, get OM3 up and running to show possible. Would be logical to use it. Timelines still quite uncertain
  • Hitting IPCC timeline means impact, but also international scrutiny of model, which is beneficial
  • COSIMA shift priorities to global, perhaps 1 deg global demonstrator which could be picked up by coupled model => implies shared codebase.
  • Also issue of porting of WOMBAT to MOM6.
  • CM work can start with NCAR 1 degree configuration @dougiesquire got working. Can use this as a test-bed to work out coupler, land-masks, fractional land cells etc. UM coupling still under development. Have working AMIP config working with a data model. Not proper two-way coupling yet. No technical challenges to it working.
  • UM work can be done in parallel with OM3 and bolted on later
  • Yes, COSIMA wants to go down this path to facilitate CMIP plan
  • Initial conditions ok. Forcing will use CDEPS datm and driver models to provide JRA or ERA5 forcing to the model. Not planning to port yatm. Should mean more forcing products can be used, and flexibility in blending forcing products.
  • Low res configs @dougiesquire has set up are using CESM input files and parameters. Do we want to use these, and topography? Or harmonise with previous OM2 configs?
  • Start with CESM inputs and gradually change?
  • Benefits: OM3 part of CM3/ESM3 would be a big tick on COSIMA grant proposal. Important achievement. If can know it possible can get ready in time, will have leveraging effect on community. If can’t manage, then impetus will fade. Needs thought about plan, who is available etc. If delay too much will not be an option. Risks in delay large. Risks in starting are small.
  • Planning 1/4, 1/10 and 1/25 global. Note sure if 1 degree necessary? 1 degree is useful from a technical pov, testing wombat etc.
  • @paulleopardi if 1 degree useful for optimisation, might be useful. Use fewer cores and vectors might end up similar length.
  • For climate/ESM 1 degree still the main workhorse. 0.25 used, but as high as currently used
  • Look at points of failure, technical challenges, performance bottlenecks. Identify pitfalls and how quickly they can be dealt with.
    – Some questions about maturity of C-grid CICE6? Coupling is via A-grid, even though model on C-grid. Might be dealt with at Bluelink meeting.
  • Should ACCESS-NRI formally be part of CICE6 consortium? Some resourcing requirements (FTEs per year)
  • Focus on CMIP7 potentially puts wav watch on the back burner. Work for CM3 doesn’t include a wave component. Already have coupled version with wavewatch, but will be focussing on coupled model parameterisations.
  • Wavewatch is important for atmospheric boundary layer. But don’t put in immediately. Could have there and turn on? Plan was always MOM6/CICE6 first, so sooner that is ready sooner we can add in Wavewatch.
  • Close to distributing a technially working ACCESS-OM3 with wavewatch that interested parties could test and feedback
  • Vision is to be able to switch out components for testing, so data ocean for testing wavewatch
  • What are next steps of MOM6/CICE6 configuration? @dougiesquire has a “thrown together” config, low level of confidence in outputs. Happy to share, but very likely to have issues. Made them work with payu.
  • Initial WW3 coupled MOM6-SIS2 config (GitHub - shuoli-code/MOM6_WW3_SIS2_coupled)
  • Configs using development version of WW3 for coupling to CICE6. Parameter settings seemed to be missing/confusing.
  • Put @dougiesquire’s config on GitHub? Will work out of the box with new build system executable
  • Build system is 90% done.
  • Merge payu driver.

ParallelIO in CICE6

  • Same as that in CICE5? Does that need to be worked on?
  • There is Parallel in CICE6. Not sure how performant it is.
  • Parallel scaling at high resolution a later concern, focussing on climate initially.

@micael I missed some of the detail of the scaling stuff at the beginning, so please do fix that up, I was intentionally fairly vague because I wasn’t exactly sure.

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Notes from the COSIMA TWG meeting today. Feel free to add whatever I’ve missed or to modify anything that I got wrong.

Date : 2023-04-12
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Aidan Heerdegen @Aidan, Paul Leopardi @paulleopardi, Martin Dix @MartinDix, Dougie Squire @dougiesquire, Rui Yang @rui.yang, Russ Fiedler @russfiedler, Angus Gibson @angus-g


  • We now have something that compiles.
  • We are using the CESM driver.
  • There are still a few things to fix, but it should be possible to test the model.
  • Next step is to try to run some tests.
  • Spack is being used to build some of the dependencies on Gadi.
  • Spack configuration has some issues:
    • Packages are installed on /scratch.
    • Some environment modules do not modify the paths, so the libraries cannot be find by the loader
  • payu support also needs some fixes and improvements.

MOM6-SIS2 scaling and profiling

  • Still not clear what is causing the MPI imbalance.
  • Imbalance present both in global and regional model.
  • Rui Yang is looking into profiling the I/O.
  • Micael will get in touch with Marshall Ward to see if he has any ideas.

ACCESS-NRI Intake catalog

  • ACCESS-NRI wants to provide a catalog of intake-esm catalogs.
  • Dougie has been working on this and has a proof-of-concept ready.
  • Feedback is most welcome at this stage.

Hi folks,
Not sure if this is the right place to ask but I see WW3 mentioned in these notes…

I’m aware ACCESS-NRI has plans to couple WW3 to ACCESS, is that part of the full coupled model/ESM, or specifically in the COSIMA space, ie ACCESS-OM?
Asking as I know things have moved on a lot in recent years with hooks being added for OASIS coupling for the UM (e.g. Extend parameter set for coupled modelling · Issue #206 · NOAA-EMC/WW3 (, just as a sort of FYI we had a postdoc here in CSIRO about 8 years ago who did early investigations into coupling ACCESS to WW3 (focussing on the atmospheric side), I really need to reclaim some disk space on Gadi so I’m just in the process of archiving her work. It’s back with v7.3 of the UM so it’s probably so out of date to be useless anyway but I thought I’d just put a callout here in case anyone wants it kept slightly more accessible for reference in future NRI work?
Honestly I think recent progress in WW3 would negate anything she’s done, I’m just keeping it for historical record, but if it’s of interest please let me know.


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For ACCESS-OM3 (MOM6-CICE6-WW3) COSIMA has switched to using ESMF/NUOPC coupling (specifically CMEPS) instead of OASIS, as discussed here. The vision is for this to be coupled to the UM (again with NUOPC) for ACCESS-CM3 - e.g. see slides 17-22 of my presentation at the 2022 COSIMA workshop. ACCESS-OM3 is in very early development, and currently using the latest development version of WW3, i.e. newer than the current 6.07.1 release which is 4 years old.

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Thanks Andrew, that’s useful. Most of my info on COSIMA is from your Bluelink Science Meeting preso which did not go into so much detail :slight_smile:
And yeah, it’s pretty hard to justify using the current production version of WW3 for much developmental work at the moment given its age and the large amount of additional capability that’s since been added!
Thanks, I will duly consider Elodie’s work to be entirely historical and proceed to archive.

Notes from last week’s COSIMA TWG. Feel free to add whatever I’ve missed or to modify anything that I got wrong.

Date : 2023-08-09
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Aidan Heerdegen @Aidan, Paul Leopardi @paulleopardi, Dougie Squire @dougiesquire, Rui Yang @rui.yang, Angus Gibson @angus-g, Harshula Jayasuriya @Harshula, Ezhil Kannadasan @ezhilsabareesh8, Siobhan O’Farrell @sofarrell

MOM6 Test Cases

  • Call is out for MOM6 test cases (see A call for community model configurations that use MOM6)
  • Question about how to do run the tests in practice from a technical point of view (see Technical requirements for MOM6 node testing):
    • How to launch test on gadi now that access-dev is going to be decommissioned? Should we use github actions?
    • ACCESS-NRI is working on setting up CI infrastructure (VM on Nirin running github runners)
    • Tests can be set up while waiting for infrastructure. Start with one test (e.g., Panan) to work out process.
    • Should tests go to a git repository, just like mom6-examples? Too much maintenance?
      • Depends on how similar tests are to production. Should be fairly close, so production configs get tested.
      • Maybe we could patch production configs for tests - eg shorter run, fewer diagnostics
      • We should use Payu. NRI needs to be broader, since other models use rose/cylc.
    • How to deal with cases that aren’t bitwise reproducible, but close enough? We can start with manual checks. MOM6 PR’s usually have notes as to whether bitwise reproducibility is expected
    • MOM consortium requires nomination of someone to sign off on tests. Suggestion for Angus to do it, plus someone else as backup.


  • Setting up new configuration to be close to OM2
    • grids etc done, JRA55-do done, separate PRs, need to merge once crash is fixed; parameter settings still need attention.
  • Ongoing comparison of ACCESS-OM3 and CIME builds. Still some differences in results, but closing in. Checking compiler flags, including for dependencies.
  • Found mismatched constants between model components
    • defaults in code; can be overridden via input at runtime
    • see what parameters CIME fixes
  • Will tag configurations and executables matching CIME builds as a starting point, and have history for reproducibility.
  • Shioban noted that CICE6-WW3 configuration doesn’t run properly because DOCN needs to supply additional fields, and NUOPC cap for CICE6 needs options to pick up ocean currents from DOCN.

ACCESS-OM3 Release Process

  • A release of ACCESS-OM3 should include all the things needed to reproduce a given run: codebase, spack env, configs, inputs.
  • We would like to have the same version number in all tags
  • Open questions:
    • how to version the inputs?
    • how about CI docker images - tag those?
  • ACCESS-NRI release team working on these issues.
    • If NRI does releases, NRI will take responsibility for tests, updates to software stack
    • OM3 can be a test case to see what works
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Notes from last week’s COSIMA TWG. Feel free to add whatever I’ve missed or to modify anything that I got wrong.

Date : 2023-09-13
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Aidan Heerdegen @Aidan, Dougie Squire @dougiesquire, Angus Gibson @angus-g, Ezhil Kannadasan @ezhilsabareesh8, Siobhan O’Farrell @sofarrell, Jo Basevi @jo-basevi , Martin Dix @MartinDix


  • 2 releases:
    • 0.1.0: this mimics the CESM version we started with (over one year old)
    • 0.2.0: updated to newer CESM - nearly cutting edge
  • Refined release process:
    • all inputs, exes, configs, spack, CI tagged simultaneously, even if unchanged from previous tag
    • input directories are also named for the same tag
    • development tag is x, e.g 0.x.0 is 0.* dev branch
  • Work on configurations:
    • One git repository for config, different flavours (e.g., forcing, grid resolution) are branches
    • Currently 2 long-lived branches in MOM6-CICE6
      • the CESM compset, unmodified - for testing only
      • 1deg JRA55do RYF - OM3 candidate
    • work already done to be like OM2, but need to update these to be compatible with 0.2.0
    • main not used for configurations - just a README explaining to check out a branch
    • some documentation on git practices Git practices · COSIMA/access-om3 Wiki · GitHub

AH: suggests as you are already using complete paths in config.yaml to individual files (not dirs) you can then do away with having a tagged dir for each release, and only update paths to files that have changed. You can use a database for finding out which configs use a given input file.
MO: we’ll see how we go with the current plan - it’s not that onerous.


  • Short term:
    • keep working on configs
    • parallelisation, scalability, processor layout options with NUOPC
    • at present all components are using all 48 cores, so components run one after the other

AK: would be good to check scaling for the sort of core count we expect to use, eg ~200 cores for 1deg. Want to use more than 1 node.
MO: need time per iteration for each component as a function of core count, so concurrently running components complete in a similar time. Currently all components run in serial, whereas in OM2 they run in parallel. Probably we want a combination of both.
DS: there are files in config giving core counts for components on different machines - could be useful as a reference for scaling. For fully active config, atmospheric component is hardwired in driver to never run concurrently with land or ice, so they should be overlapped on PEs.

MD: Kieran finds CICE restart makes whole thing grind to a halt
MO: is CICE using PIO?
MD: unsure.
DS: compiling with CIME.
MO: should be PIO then.

MD: can use current CESM-based OM3 now for coupling with UM.
AH: could start using spack to help with build.
MO:there’s a lot of logic in the cmake that you don’t want in spack - cross-dependencies between components - compilation needs to be in a particular order - can’t just compile all components separately and then link. eg driver needs to come last. And there are a couple of patches.
MO: easy to change cmake to compile all components or a subset as library without driver.

Payu Updates

  • New topic for payu updates: Payu updates at NCI - #2 by Aidan
  • “module use” implemented
  • Jo working on auto-archiving outputs from scratch by payu - should replace sync scripts
  • date-based restart pruning, following tidy_restarts - can specify pandas-style time frequency
  • issues to resolve re. collation and sync of final restarts
  • future plans: embedding and tracking uuids for reproducibility / provenance
  • facilitate multiple experiments per control directory: automatically create run branches based on uuid, also name work and archive directories with uuid to work around limited name-space issues

MO: runlogs - should only be on for production runs, not development test runs
• we’ll force users to create their run fork (or at least branch), without needing payu
• forbid direct pushes to config branches - require PRs
• runlog off by default
• config main branch only has README explaining that a branch needs to be checked out and runlog activated
• this saves work for a few developers but adds work for many users
• recommends activating runlog by default, as users will forget
MO: can be implemented by turning runlog on in tagged commits, since users should not be using dev branches.
AH: this could be a CI check.

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Notes from this week’s COSIMA TWG. Feel free to add whatever I’ve missed or to modify anything that I got wrong.

Date : 2023-10-11
Attendees : Micael Oliveira @micael, Andrew Kiss @aekiss, Aidan Heerdegen @Aidan, Dougie Squire @dougiesquire, Angus Gibson @angus-g, Ezhil Kannadasan @ezhilsabareesh8, Siobhan O’Farrell @sofarrell, Anton Steketee @anton , Harshula Jayasuriya @harshula

COSIMA Spack instance and ACCESS-OM3 deployment plans

  • We currently have 2 Spack instances at /g/data/ik11/spack, using different versions of Spack
  • We do not delete old instances in case it’s in use.
  • There’s a GitHub repo with all the configuration.
  • Includes a script to automatically create a Python virtual environment.
  • Some Spack environments are for consumption, some (unstable) are used as a development sandbox, e.g. updating OM3 dependencies.
  • Still unclear what is the best way to install the same Spack env twice with different architectures - currently can do it by logging in to different architecture nodes and recompiling, but the Spack lock file, which are kept under revision control for reproducibility, needs to be changed when changing architecture.
  • Executables are currently deployed manually to /g/data/ik11/inputs/access-om3/bin.
  • Plan is to also use the spack environments to deploy the executables:
    • module gets created automatically
    • ensures reproducibility (currently we don’t keep information about how the executable was compiled).
    • currently we don’t have a simple way to distinguish exectuables compiled for different architectures.
  • Need to add OM3 package to Spack
  • Current build system: each model component is built as a library, then all of them are linked to build the OM3 executable.

• would like OM3 in spack
• would like to build each model component separately in Spack.
• we can start by changing the OM3 CMake to install the component libraries.
• may be able to deploy OM3 from github - more seamless
• need to think about how this interacts with payu configs, so config uses correct deployment
• simplest way is to use modules
• but currently payu doesn’t look at paths for exes - needs to be hard-coded - may be better to modify payu to support this.
• need to think about how the build system will work with Rose/Cylc

ACCESS-OM3 update

  • Finished setting up 1deg configs using OM2-based settings, supergrid and topog, C-grid MOM6 and B-grid CICE6 for testing purposes (will improve these later, including C-grid CICE)

    • basically done for MOM6-CICE6
    • now need to do MOM6-CICE6-WW3
  • MOM6-CICE6-WW3 configurations:

• Added compilation of WW3 helper exes to build script - see EK below
• current MOM6-CICE6-WW3 uses predefined inputs, parameters
• need to make this tripolar, matching other model components
• requires helper exes
• have done this following Shuo Li’s config
• this creates input binary files and restart file
• now running with same grid for all model components
• now moving to look at WW3 switches (much of the functionality is set at compile time via switches)
• using a modification of version from Denisse Worthen
• we can now generate our own parameters, change grid, etc
• MOM6-CICE6-WW3 repo now has parameters based on Shuo LI
• getting help from Stefan Zieger (BoM)
• also need to look at / set up parameters to suit ice-ocean interaction
• can also see what parameters UKMO have used
• take the opportunity to move tripoles? away from Hudson Bay and Gulf of Ob

  • Understanding how profiling works in CESM was not trivial (upstream is in a state of flux)
    • it is now working via ESMF - provides nice output and includes visualisation tool.
    • Includes operations done via ESMF, ie everything in run sequence.
    • Some models (CICE6) have some profiling that can be reported to ESMF.
    • MOM6 profiling is reported via FMS not ESMF.
    • Will now test number of cores per component. Big parameter space. Aim for good-enough performance, and then optimise after we have finalised configuration.

• WW3 can cost as much as the ocean - but depends on resolution and timestepping
• but both ocean and WW3 are cheap compared to atmosphere
• can run ocean and waves in parallel or one after the other, giving different options for core counts
• need to re-do optimisation work with ww3
• were using 1hr wave and 20min ocean timestep

  • More work by DS porting WOMBAT
    • after much effort, can now run OM3 with BLING without crashing (not running correctly, but not crashing - not using coupler) - needed to add things to NUOPC cap
    • some of benefits of generic tracers are disappearing - assumes using FMS, so it will be more work than anticipated to get WOMBAT running the same way in OM2 and OM3.
    • generic tracers are tracers that run in both MOM5 and MOM6, but this is really only the case if using FMS coupler. NUOPC requires additional changes. We were hoping to be able use generic tracers to use any of the other BGC packages (BLING, COBALT) as easily as WOMBAT, but this is not likely to be easy with ESMF coupling and may also require compile-time tweaks
    • block after block after block
    • would need to hack BLING code to avoid calculating fluxes in BLING
    • NUOPC cap ignores some of the fields that need to be turned on, eg gas fluxes
    • CESM uses MARBL but this is implemented in a completely different way with a driver layer. Can run with multiple ocean models. Have made contact with software engineer; awaiting details.

AS/SO: ice testing
• test both stable and unstable
• issues with scripts breaking

Other topics

AH: payu update
• Jo is close to merging date-based restart pruning - includes checks that we’re not pruning too much (can pass flags to override)
• then will work on remote syncing - will be a hook for post-processing prior to remote sync - will be options to remove locals
• then uuid for provenance
• may want to also clone/update run repo to destination when syncing to preserve copy of run log with the data - see
• may also want to exclude some files from sync, e.g. uncollated files and *-DELETE etc from post-processing

AK: non-reproducible run
⚠️ Inconsistent ocean and sea ice in final 7.5yr of 0.1° IAF cycle 4
• payu can do reproducible runs using manifests but currently only checks inputs, not outputs
• hard to see how to ensure repro without running everything twice
• plan to re-run released experiments to detect repro problems eg with NCI updates
• could be changes on gadi, eg security patches to kernel
• also very little NCI control on firmware, which hardware vendors update
• need a mechanism to version data and withdraw bad data

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Date: 2023-10-31


Micael, Anton, Martin Dix, Matt Chamberlain, Andrew Kiss, Paul L, Dougie, Heidi, Siobhan, Harshula, Kieran, Ezhil, Aidan

New Schedule – two meetings a month for TWG now, on the first and third week.

Next one – potentially Tues 14th at 10am

BGC Coupling in ACCESS-OM3


Goal is to eventually get Wombat integrated into ACCESS-OM3.

Plan is to use the ‘generic tracers’ API in MOM6 to implement Wombat (which was implemented directly in source can in OM2).

GFDL generic tracers are written under the assumption that the FMS coupler is being used for coupling with the atmosphere ( gas flux, runoff, and others). The FMS couple is calculating some these fluxes in this case.

A plan:

Update the NUOPC cap

  • To set the initial conditions, some of this part is prototyped
  • And to include calculated tracer fluxes in the time step. This part should be able to re-use the FMS routines which do these calculations. (i.e. get the gas fields from the atmosphere, calculate in the FMS coupler routines, add the fluxes to ice_ocean_boundary to send to MOM)

Open issues:

  • implementation time longer than expected
  • How keen are we on Bling / other models

Wombat is a simpler model than Bling, has less fields to pass the coupler. So AK asked if there are efficiency gains to be made there to only couple Wombat but still using the generic tracers? But Dougie doesn’t think this would lead to add any gains.

We need to write some code to connect the Nuopc fields to a structure that the FMS coupler routines will handled. The mapping of fields could be hardcoded initially, and then made configurable later.

MC: Highlighted that we need Wombat integrated early next year to meet the goal of having an ESM for CMIP7 runs.

  • A simple ocean tracer would be faster to implement, but would then later need rework.
  • MC and DS to catch up on scoping the remaining work

Siobhan: Is chasing weights from the ERA5 runs done using OM2. Should be on GitHub


Working on coupling MOM/CICE with UM

  • Initial runs are working.
  • Using (ACCESS-NRI) development repos for CICE and CMEPS – but will probably move to patch files eventually to make version control easier.
  • Kieran and Micael are going to work together to optimise the build system – to be able to use the same build system for CM3 and OM3 (and others?)

Micael and Ezhil:

  • Working on adding wavewatch-3 to the MOM6-CICE6 configuration
  • No output from Wavewatch 3 at this point. Debug output is working, but Ezhil is working on the gridded output.
  • Tri-polar closure means that the wave propagation scheme needed to be changed.

Andrew K / Anton

  • Andrew has been looking at the MOM6 configuration
  • Anton has been looking at the CICE configuration
  • We may need to do some work to parallelise (or improve the parallelising or) the output similar to done for CICE5 (and Paul may need to do the same for CABLE).
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Date: 2023-11-14

Attendees: Micael Oliveira @micael, Andrew Kiss @aekiss, Ezhil Kannadasan @ezhilsabareesh8, Siobhan O’Farrell @sofarrell, Anton Steketee @anton, Harshula Jayasuriya @harshula, Martin Dix @MartinDix

Short meeting - just brief updates

AS, AK: Sea ice update from discussion with Hunke & Bailey

  • NCI joining cice consortium
  • Netcdf4 support to be added with chunking and compression
  • CICE Consortium User Workshop and Tutorial, May 21-23, 2024, Santa Fe (with online option)
  • CICE6.5.0 released, with C-grid support; UCAR / CESM are aiming to update their CICE fork in the next 1-2 months; however coupling is still on the A grid
  • Use ACCESS driver or flag for our CESM customisations
  • CESM find WW3 very expensive - looking at running on 3° grid; also working with wave model devs for simpler configurations - don’t need all WW3 details for climate applications
  • E3SM bug fixes and BGC improvements coming to CICE6 soon
  • CESM working on ocean-ice BGC coupling with MARBL

MD: Dougie has made good progress with BGC, solved some key problems, should have BLING working soon with generic tracers, just a few lines to change

EK: WW3 update

  • gridded output issue solved - was due to flag in cap
  • can also generate point output (spectra) - using UFS model point output, comparing with buoy data
  • ww3 can now produce netcdf directly

KR: UM coupling update

  • can build using MOM6, CICE6 library version
  • continuing CICE6 coupling work
  • sorting out tech issues passing ungridded dimensions (ice categories)
  • SO: also need to resolve imports and internal stuff in CICE6 to calculate skin temp etc
  • MO: ran into a few lib problems - working on it

MO: some payu updates for spack in discussion

Next meetings: Wed 6, 20 Dec

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Meeting Minutes

Date: December 7, 2023


Changes in Meeting Format:

  • First monthly meeting dedicated to updates from TWG.
  • Second monthly meeting focused on discussing issues, planning, and prioritizing work.


  • Developed the IAF Configuration for MOM6-CICE6-WW3.
  • Compared MOM6-CICE6-WW3 IAF data with NDBC buoy data; good match for lower HS, deviation for larger HS.
  • Resolved a bug in existing MOM6-CICE6 IAF configuration; year_align in IAF should match year_start in streams XML.

Discussion on year_align for RYF Configuration:

  • Correct year_align crucial to avoid incorrect forcing.
  • Debate on ideal year_align for RYF: use 1900 (start of RYF dataset) or 0000 (simulation start year).


  • Completed first successful om3 run with bling, focusing on CO2 and O2 concentrations.
  • Addressed handling of fields not provided by the atmosphere.
  • Discussed reading capabilities for files not provided by model components.


  • Identified a bug in openmp hindering parallel reading.
  • Working on adding chunking info to CICE output.
  • Progressing with CICE standalone on Gadi; exploring different CICE versions and potential CICE6-WW3 integration using NUOPC.


  • Discussed git workflow for patch file creation and PRs; emphasized unified repo and configuration branching.
  • Collaborating on name list file comparison between configurations.
  • Covered profiling challenges, work with cmake, and Python scripts for configuration management.
  • Raised questions on the applicability of optimization tools across different models.


Two-Week Planning:

  • Ezhil: Continue development and analysis in IAF configurations, comparison with satellite data and seek BOM assistance to check the flags and input parameters of ww3.
  • Anton: Finalize CICE standalone; collaborate on analysis recipes.
  • Dougie: Assess output from coupled bling runs; seek NCAR MOM assistance.
  • Michael: Prioritize optimization and profiling for an OM3 configuration.

Next Meeting:

  • Scheduled for December 20, 2023, to discuss further planning.