Version 18 (modified by clevy, 3 years ago) (diff)


The PI is responsible to closely follow the progress of the action, and especially to contact NEMO project manager if the delay on preview (or review) are longer than the 2 weeks expected.

  1. Summary
  2. Abstract
  3. Implementation
  4. Reference manual and web pages updates
  5. Preview
  6. Tests
  7. Review


Action VALID-12_CLEVY_CoupledInterface
PI(S) C. Levy


Validation of NEMO coupled interface, using OASIS in the trunk (as future 4.0 release)

Expected for
Ticket #2147
Branch NEMO/branches/$YEAR/dev_r{REV}_{ACTION_NAME}
Previewer(s) S. Masson, R. Hill, E. Maisonnave
Reviewer(s) S. Masson, R. Hill, E. Maisonnave

'.' => '/nemo/wiki/2018WP/VALID-12_CLEVY_CoupledInterface'


The NEMO OASIS interface is important for all coupled configurations. Testing that this section (mainly the coupling activated) is functional must be done before the 4.0 announcement.


To check if the coupling interfaces are functional, three steps/tests will be set up:

STEP1: Validation of the SAS reference configuration

STEP2: Set up a test using NEMO (starting from the global reference configuration) with key_coupled, OASIS active and a toy atmospheric model

STEP3: Using this configuration, check that the coupled interface is functional for ocean dynamics, sea ice and biogeochemistry

Reference manual and web pages updates

Not done yet


Since the preview step must be completed before the PI starts the coding, the previewer(s) answers are expected to be completed within the two weeks after the PI has sent the request to the previewer(s).
Then an iterative process should take place between PI and previewer(s) in order to find a consensus

Possible bottlenecks:

  • the methodology
  • the flowchart and list of routines to be changed
  • the new list of variables wrt coding rules
  • the summary of updates in literature

Once an agreement has been reached, preview is ended and the PI can start the development into his branch.

For this taks, no development is scheduled: the goal is only to check that the coupling interface of NEMO 4.0 is working.
The advice of previewer on the list of proposed tests is of course welcome.


Once the development is done, the PI should complete the tests section below and after ask the reviewers to start their review.

This part should contain the detailed results of SETTE tests (restartability and reproducibility for each of the reference configuration) and detailed results of restartability and reproducibility when the option is activated on specified configurations used for this test

Regular checks:

  • Can this change be shown to produce expected impact (option activated)?
  • Can this change be shown to have a null impact (option not activated)?
  • Results of the required bit comparability tests been run: are there no differences when activating the development?
  • If some differences appear, is reason for the change valid/understood?
  • If some differences appear, is the impact as expected on model configurations?
  • Is this change expected to preserve all diagnostics?
  • If no, is reason for the change valid/understood?
  • Are there significant changes in run time/memory?

TEST1: Validation of the SAS reference configuration

The reference configuration ORCA2_SAS_LIM has run sucessfully for one year using the set up defined in the NEMO shared reference (NEMO trunk rev 10272).
It has been compared with a one year run of the forced reference configuration ORCA2_ICE_PISCES (NEMO trunk rev 10272).

Validation of the results:

  • Some questions raised on the forced configuration itself, see below
  • After one year experiment, the ice restart file is created in the SAS run and looks like a correct ice restart file
  • Having a complete an exact validation of this configuration will need some more work: here the ice is forced with an ocean input file containing the surface fields. These fields are not varying with time for now in the input file. To have a complete validation, it would need:
    • to run a one year of ORCA2_ICE_PISCES full reference configuration, with outputs of these daily surface fields
    • to use this output as input to the SAS configuration
    • to make some subtle changes in SAS in order to have the exact same use of these fields in time (not the case for now, work done once by Sébastien and Eric, remaining to be taken in account again
    • Once all this is done, the ice restart file should be strictly identical between the ORCA2_ICE_PISCES run and the ORCA2_SAS_LIM one

This work has not been done at this stage, so that for now the conclusion is:
The ORCA2_SAS_LIM configuration is running in NEMO 4.0, e.g. the SAS interface is functionnal in this case.

Comments on forced reference configuration ORCA2_ICE_PISCES :
The reference configuration is set up to start from rest (e.g. the very initial start, no ocean restart at all). In this case, using a call frequency of the ice =3 , nn_fsbc=3, is unstable: the run crashes after a few tenth of timesteps. Using nn_fsbc=5 (e.g. ice called every 5 timesteps, inducing less high frequencies in the forcing since the mean value used is calculated on a longer time scale), the model runs fine. This instabilities was not expected in the ORCA2 configuration, usually considered as very stable. Still this nn_fsbc=5 values has always been used up to now…
Once the ocean has started, after a few years, it seems that the nn_fsbc=3 option is indeed stable enough.

TEST2: Set up a test using NEMO (starting from the global reference configuration) with key_coupled, OASIS active and a toy atmospheric model

Using this configuration, check that the coupled interface is functional for ocean dynamics, sea ice and biogeochemistry

  • OASIS3-MCT version is installed, revision xxx
  • a CPL_TOYATM configuration is created, based on ORCA2_ICE_PISCES, and with oasis cpp keys key_oasis3 key_oa3mct_v3 active is created
  • First compilation problem, requests a fix in oasis for now (see attached file in the ticket #2147 )
  • The toyatm developped by Eric Maisonnave is compiled as a simple toy for the atmosphere
  • iodef.xml modified for OASIS use
  • the number of (fake) fields is adjusted in the namcouple and namelist_cfg files
  • Coupling frqequence is set to 1 (every time steps)
  • Test is short (5 timesteps, since the atmspheric fields are constant in space and time and not realistic)
  • The run is completed

Validation: the NETCDF file of SST seen by the toy atmosphere looks reasonable.

The global 2° configuration in a very simple coupled mode using OASIS is running fine with NEMO 4.0, e.g. the OASIS interface between ocean dynamics, sea ice and atmosphere is functionnal.


As a result of the tests, a few things needs to be updated/fixed:

  • sbccpl.F90
  • namelist_ref

A new test case has been build with a toy for the atmosphere (proposed name for this new test case: YAZD, for Yardstick Atmosphere to Zero a Demonstrator, since yazd is an oasis in Iran…). It is proposed to add this configuration in the list of available test cases.


A successful review is needed to schedule the merge of this development into the future NEMO release during next Merge Party (usually in November).


  • Is the proposed methodology now implemented?
  • Are the code changes in agreement with the flowchart defined at preview step?
  • Are the code changes in agreement with list of routines and variables as proposed at preview step?
    If, not, are the discrepancies acceptable?
  • Is the in-line documentation accurate and sufficient?
  • Do the code changes comply with NEMO coding standards?
  • Is the development documented with sufficient details for others to understand the impact of the change?
  • Is the project literature (manual, guide, web, …) now updated or completed following the proposed summary in preview section?


Is the review fully successful? If not, please indicate what is still missing

Once review is successful, the development must be scheduled for merge during next Merge Party Meeting.

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