ACCESS-CCM
Contents
ACCESS UKCA Coupled Model
Scott Wales, ARCCSS CMS
Introduction
ACCESS UKCA Coupled Model (ACCESS-CCM) is a global earth-system model aimed at representing interactions between atmospheric chemistry and the oceans. It is based on a pre-release version of ACCESS-CM 2, with the atmospheric component replaced by a UM 8.4 model configured for GA4 with UKCA enabled.
Model Components
The model components are:
- Atmosphere: UM 8.4 https://access-svn.nci.org.au/svn/um/branches/dev/saw562/8.4/coupled-ukca
- Land Surface: JULES (UM 8.4) https://access-svn.nci.org.au/svn/jules/trunk@234
- Sea Ice: CICE 5 https://access-svn.nci.org.au/svn/cice/branches/access/cice5@313
- Oceans: MOM 5 https://github.com/hailinyan/mom @44dd691f
- Coupler: OASIS3-MCT 2.0 http://oasis3mct.cerfacs.fr/svn/branches/OASIS3-MCT_2.0_branch/oasis3-mct
The UM8.4 source code has been modified to use the ACCESS coupling, the other models are unchanged from the ACCESS-CM2 versions
Model Configurations
The atmosphere and land surface configuration is based on the Accessdev UMUI job ‘vabqa: GA4.0 UKCA StratTrop+MODE’, which corresponds to the Monsoon UMUI job xhmaj [1].
The ocean and sea ice configuration comes from the ACCESS-CM2 development model
[1] http://www.ukca.ac.uk/wiki/index.php/Vn8.4_GA4.0_Release_Candidate:_RC6.2
Using the Model
Run Scripts
The coupled model run scripts are held in version control, at the URL https://access-svn.nci.org.au/trac/access/browser/branches/access-cm2-ukca. If you want to modify the model you should create your own branch of this and commit back regularly, if you just want to run the model check out the scripts with:
svn co https://access-svn.nci.org.au/svn/access/branches/access-cm2-ukca access-cm2
There are two directories of interest here - ‘submodels’, where the model executables are built, and ‘exp’, which contains experiment configurations. The runscripts themselves are at exp/n96-ukca}}, the file {{initial can be changed to set the following information:
Run Dates
The model uses a 360 day calendar, as was used in the original UKCA configuration. To set the start and end dates of the model, change the following variables in the file ‘initial’
- Start date: iniyear, inimonth, iniday
- End date: finalyear, finalmonth, finalday
Resubmission
To change how long each restart segment runs for change the following variables in the file ‘initial’. Ensure UM restart dumps are output at least this often
- Restarts: nyear, nmonth, nday
Initial Conditions
To change the initial conditions file change the variable ‘um_astart’ in the file ‘initial’. The initial conditions file should be reconfigured according to the instructions in the ‘Atmosphere Reconfiguration’ section
- UM Initial Conditions: um_astart
- MOM & CICE Initial conditions: inputdir2b (~access/access-cm2/input_b)
Compilation
To build the model run the ‘build.sh’ script in the top-level directory. This needs to be run on Raijin’s login node so it can download the model source codes, but it will then submit the actual build jobs to the express queue.
Atmosphere Namelists
The atmospheric settings can be changed by editing the namelist values, but it is recommended that they be set via the UMUI so that values are consistent.
On Accessdev, make a copy of the UMUI job valro, which is vabqa with coupling enabled. Make any modifications, then process the job. This will create a set of namelists in the directory ~/umui_jobs/RUNID, where RUNID is the UMUI’s job identifier. Copy the contents of this directory to your experiment’s ‘umui’ directory on Raijin, eg.
rsync -rv accessdev:~/umui_jobs/vabcd/ ~/access-cm2/exp/n96-ukca/umui
Note that if you change the model’s start date in the UMUI you’ll also need to change the run scripts to reflect this, see ‘Job Submission’
Atmosphere Reconfiguration
The reconfiguration process ensures that fields required for atmospheric chemistry and ocean coupling are present in the initial conditions file. To perform a reconfiguration process & submit the UM job being used for the coupled run in the UMUI.
Reconfiguring produces a file on Raijin named /short/$PROJECT/$USER/UM_ROUTDIR/$USER/$RUNID/$RUNID.astart, where $RUNID is the UMUI job identifier. The path to this file should be set in the coupled model initialisation script exp/n96-ukca/initial as the variable um_astart so that it gets picked up by the model run.
Job Submission
To submit the job as-is go to the experiment directory (e.g. access-cm2/exp/n96-ukca) and run
qsub access-cm2
Model Output
Model output may be found in the directory /short/$PROJECT/$USER/archive
Coupling Changes
The ACCESS-CCM coupling sequencing is slightly different to ACCESS-CM, primarily to minimise code changes. The atmosphere reads ice and ocean variables from the previous timestep, while the ice and ocean models read atmospheric variables from the current timestep. In the original ACCESS-CM both the atmosphere and ice fields were read from the previous timestep.
Resource Requirements
Resources for different decompositions are as listed:
| Atmosphere CPUs | Ice CPUs | Ocean CPUs | Walltime per Model Month | SU per Model Month | Memory |
| 224 | 16 | 16 | ~ 2 hr | ~ 500 | < 30 GB |
Load balance: (0-223 ATM, 224-239 ICE, 240-255 OCN)
| Atmosphere CPUs | Ice CPUs | Ocean CPUs | Walltime per Model Month | SU per Model Month | Memory |
| 288 | 16 | 16 | ~ 1.5 hr | ~ 500 | < 30 GB |
Load balance: (0-287 ATM, 288-303 ICE, 304-319 OCN)
| Atmosphere CPUs | Ice CPUs | Ocean CPUs | Walltime per Model Month | SU per Model Month | Memory |
| 352 | 16 | 16 | ~ 1.3 hr | ~ 650 | < 30 GB |
Load balance: (0-351 ATM, 352-367 ICE, 368-383 OCN)
