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'''Author''' : Chris harris

'''ticket''' : #665

'''Branch''' : https://forge.ipsl.jussieu.fr/nemo/browser/branches/2011/dev_r2802_UKMO8_sbccpl and https://forge.ipsl.jussieu.fr/nemo/browser/branches/2011/dev_r2802_UKMO8_cice 
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=== Description ===

The sbccpl branch provides a more flexible namelist-controlled version of the code for interfacing with an atmosphere model (including the ability to deal with multi-category sea ice fields for LIM3 / CICE, and to receive the extra heat flux fields used when running the UM atmosphere with NEMO and CICE).  The new namsbc_cpl namelist controls whether a particular coupling field will be multi-category or not and in simple cases the code will perform relevant transformations as required (e.g if requesting single category coupling fields when running with multiple categories in LIM3 / CICE).  The OASIS3 coupling field names will be generated automatically, but must be consistent with the contents of the OASIS namcouple file.

When running with CICE (either fully coupled, or ocean-ice only) the dev_r2802_UKMO8_cice is also required.  The code changes have been separated for ease of testing etc, but will be merged together before committing to the trunk.  The commit message for changeset [2874] provides some more details on the CICE interface code.

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=== Testing ===
Testing could consider (where appropriate) other configurations in addition to NVTK].

||NVTK Tested||'''NO'''||
||Other model configurations||'''YES'''||
||Processor configurations tested|| 4x8, 8x4, 5x6, 6x5 ||
||If adding new functionality please confirm that the [[BR]]New code doesn't change results when it is switched off [[BR]]and !''works!'' when switched on||'''YES'''||

(Answering UNSURE is likely to generate further questions from reviewers.)

Tested in NEMO-CICE and UM-NEMO-CICE and any changes from previous local code are understood (e.g. due to bug-fixes) or very minor (due to bit level changes).

Code compiles with key_lim2, key_lim3 and without a sea ice model (both standalone and with key_oasis3).

=== Bit Comparability ===
||Does this change preserve answers in your tested standard configurations (to the last bit) ?||'''YES'''||
||Does this change bit compare across various processor configurations. (1xM, Nx1 and MxN are recommended)||'''YES'''||
||Is this change expected to preserve answers in all possible model configurations?||'''NO'''||
||Is this change expected to preserve all diagnostics? [[BR]],,''Preserving answers in model runs does not necessarily imply preserved diagnostics. ''||'''YES'''||

If you answered '''NO''' to any of the above, please provide further details:

These code changes will not have any impact on any of the standard NEMO configurations with do not involve coupling to an atmosphere model (all changes either concern the coupling routines, or are protected by key_cice).  Depending on the exact namelist options used, results when running an atmosphere-NEMO-LIM2 coupled model may be affected due to some bug-fixes in sbccpl, and changed order of summations which may have an impact at the bit level.

For NEMO-CICE, tests have included 4x8, 8x4, 5x6 and 6x5 - all these give identical results using the PCG solver (with key_mpp_rep). 

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=== System Changes ===
||Does your change alter namelists?||'''YES '''||
||Does your change require a change in compiler options?||'''NO'''||

New version of namsbc_cpl for ORCA2-LIM2 supplied in https://forge.ipsl.jussieu.fr/nemo/browser/branches/2011/dev_r2802_UKMO8_sbccpl.

key_cice required for running with the CICE sea ice model.  Currently a number of minor code changes are required in CICE although by the time of the NEMO 3.4 release it is expected that these will have been incorporated in the CICE trunk at LANL.

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=== Resources ===

No significant resource implications - memory usage in fully coupled mode should be slightly lower due to fewer unused arrays being allocated.

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=== IPR issues ===
||Has the code been wholly (100%) produced by NEMO developers staff working exclusively on NEMO?||'''YES'''||

If No:

 * Identify the collaboration agreement details
 * Ensure the code routine header is in accordance with the agreement, (Copyright/Redistribution etc).Add further details here if required..........