# COSIMA TWG Meeting Minutes 2024 **URL:** https://forum.access-hive.org.au/t/cosima-twg-meeting-minutes-2024/1734 **Category:** TWG **Tags:** meeting, twg, notes, minutes **Created:** [17 January 2024 05:11 UTC](https://forum.access-hive.org.au/t/cosima-twg-meeting-minutes-2024/1734 "2024-01-17T05:11:58Z") **Posts on this page:** 1 **Showing post:** 17
### Author: ![aekiss](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/aekiss/32/46_2.png) [@aekiss](https://forum.access-hive.org.au/u/aekiss) #### Post date: [18 September 2024 01:13 UTC](https://forum.access-hive.org.au/t/cosima-twg-meeting-minutes-2024/1734/17 "2024-09-18T01:13:24Z")
Summary from TWG meeting today - please correct and elaborate as needed. **Date:** 2024-09-18 **Attendees:** - Adele Morrison (AM)@adele-morrison - Andy Hogg (AHogg) @AndyHoggANU - Andrew Kiss (AK) @aekiss - Anton Steketee (AS) @anton - Siobhan O’Farrell (SO) @sofarrell - Chris Bull (CB) @cbull - Helen Macdonald (HM) @helen - Martin Dix (MD) @MartinDix - Angus Gibson (AG) @angus-g - Harshula (HJ) @harshula **AM: CLIVAR OMDP meeting** (on the side of [CLIVAR/COMMODORE](https://forum.access-hive.org.au/t/ocean-model-development-and-machine-learning-meeting-in-boulder/1941)) - OMIP papers being prepared, eg - Fox-Kemper on diagnostics and forcing strategy and protocol - Gokhan: ocean spinup - ocean-sea ice data request - First phase to use JRA55-do 1.5 - Gokhan leading ERA5-based forcing ([CFORCE](https://github.com/COSIMA/access-om2/issues/247#issuecomment-1951481016)) for the next phase of OMIP - person doing work only just started - testing by NCAR/GFDL/ Los Alamos. We’ll do 2nd stage testing (with others) - Plan to update to ERA6 when avail - Bill Large leading revision of bulk formulae - Discussion on spinup protocol - Moving away from 4x61-year cycles to avoid warm → cold jump from 2018 → 1958. - Maybe repeat decade for several cycles, then IAF at end. TBC. - Advantage of repeat decade is inclusion of interannual variability in spinup, and closer to climatology than a single-year RYF. - But could make validation awkward if repeated decade is (say) 1958-1968, since both forcing and obs are poor. But later decades include more climate change signal. - Relative or absolute winds - in discussion. Eric Chassignet in favour of mixed (70% of ocean vel). But depends on how ERA5-based forcing is developed - Whether to use SSS restoring - previously problematic, with differing parameters and issues extending into future. - [Harrison et al 2022](http://dx.doi.org/10.1029/2021MS002888) switch off salinity restoring and have freshwater transport between latitude bands based on CMIP models, and land storage in each band to have delays. Fixed many biases eg AMOC and T drift in spinup. Suggest using this instead of SSS in OMIP, with atm and land bulk reservoirs. Other groups unsure. - Multiple groups to test this, **including us**. Details to come (Adcroft/Harrison). Invite Adcroft/Harrison to present on this at a COSIMA meeting? [NB: this has now been scheduled for the [COSIMA meeting](https://forum.access-hive.org.au/t/cosima-working-group-announce/238) on 14 Nov 2024] - We should follow OMIP protocol to facilitate comparison with other OMIP studies. CB: what’s the plan for spinup, given we won’t have finalised OMIP? AH: go with something consistent with ACCESS-OM2 for comparison AM: why match with OM2? why not match best with obs? AH: two objectives: 1: good enough for coupled modellers (benchmark=OM2); 2: perfect the OM3 model, eg using repeat decade etc from OMIP **AH: [COMMODORE meeting](https://forum.access-hive.org.au/t/ocean-model-development-and-machine-learning-meeting-in-boulder/1941) updates** - quite technical - 5-6 engineers there, including some talks - ACCESS-OM2 bottom water was news to many attendees, and some were unaware the AABW shouldn’t be from open-ocean polynyas - emphasis on Gulf Stream separation to justify high res AM: - lots on machine learning, eg for parameterisations; danger of us falling behind? - a lot of work on climate model emulators AK: - [Theresa Morrison](https://usclivar.org/abstract-micro-2024/improving-dynamic-coupling-sea-ice-and-ocean-models) on sea ice/iceberg -ocean coupling without levitation by coupling at barotropic timestep - [Carolin Mehlmann](https://usclivar.org/abstract-ocean-model-2024/hybrid-ice-model) on hybrid sea ice / iceberg melange AM: what are our options for icebergs? Can CICE6 do it? AS: unclear what is being done. Was work ~10yr ago with icebergs in CICE but not coupled to ocean AM: What about distributing iceberg flux in OM3? We should spread according to a prescribed pattern rather than at coast. See [issue](https://github.com/COSIMA/access-om3/issues/225). - Martin/Siobhan/Chris: at the moment we have HADCM3 seasonal climatology from coupled run - Chris: has used interannually-varying iceberg distribution - Adele: any spread is better than nothing - Andes : about 50% at the coast, 50% spead by distribution - Anton: Who to take this on? AS: @minghangli’s tracer timestep investigation: - seem to be settling on 3hr irrespective of resolution - to be tested at 0.25° AS: @ezhilsabareesh8 progressing well with new grid - error of too many CFL truncations - log files not working? NCMAS - NCMAS applications are likely open soon, although they appear delayed. We need numbers scaling performance for both OM2 and OM3. Its hard to provide solid OM3 numbers at this point. - AM: need good numbers to include OM3 in proposal. Last year’s application was criticised for lack of OM3 detail - few proposals in this round are likely to need OM3 Andy: OM3 evaluation - had a lot of test cases lined up - timing, timestepping etc needed to be done first - now basically done - revisit test plans, or proceed with plans? - strategy of something decent for CM3, then refine - run and analyse all, or involve community in analysis and/or runs? Anton: Best case is with tracer time-step and new grids, OM3 will be stable and efficient enough for CM3 without further investigation. C-grid cice testing to be done still at 0.25° - expect to be ok. Andrew: for refinements after an intial version of CM3, we want to be able to keep those in sync Martin: @kieranricardo has custom mediator and different build process, using OM3 object file as library. But OM3-CM3 upgrade path fairly frictionless so can adopt OM3 changes easily. Adele: for [model evaulation](https://forum.access-hive.org.au/t/access-om3-evaluation/) we need to get COSIMA to agree on a priority list of metrics and acceptable values (eg T bias, AABW formation rate, etc), and ideally to write assessment scripts - Andy: Cookbook or ESMvaltool? - Anton: going with Cookbook style - lots of overhead with ESMvaltool - Andrew: want to avoid additional barriers to engagement - already have MOM6, etc - Andy: need a plan and timeline once we have Ezhil’s version stable and Minghang’s timings COSIMA leadership meeting at [Australian Antarctic Research Conference](https://forum.access-hive.org.au/t/australian-antarctic-research-conference/2070), Hobart 19-22 Nov - intro movie - ethics - attribution/credit AK: For a later discussion: post-CMIP7 priorities: high resolution? BGC? WW3? DOCN? @lgbennetts is [keen on CICE-WW3-DOCN](https://forum.access-hive.org.au/t/access-om3-evaluation/1462/13) but needs excessive wave attenuation to be resolved (perhaps with [this bugfix](https://github.com/cmbitz/WW3Numerics)? need to wait until available in [ESCOMP](https://github.com/ESCOMP/WW3/) before we test it in OM3) --- _[View the full topic](https://forum.access-hive.org.au/t/cosima-twg-meeting-minutes-2024/1734)._