Last edited Timestamp?

Author : acc (on behalf of agn)

ticket : #680

Branch : DEV_r1924_nocs_latphys

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Description

This branch will contain the latest version of Griffies's implementation of the Gent and McWilliams? eddy transport as a skew flux. This has the advantage that its numerical discretization can be written in terms of contributions from quarter cells – ‘triads’. This gives a tighter stencil, disallowing 2-gridpoint numerical noise that is permitted by the advective discretization. A working prototype code for the iso-neutral and skew-flux operator was carefully reviewed in 2009. Considerable care has been taken in the formulation to ensure the tensorial representation is consistent with the variable volume layers (s-coordinate/z* representation). This has been documented and will be provided with the release.

Method

(1) Discretise Isopycnal diffusion in terms of these triads. This will obviate the need to smooth isopycnal slopes horizontally with a Shapiro filter (as currently implemented in NEMO), or to apply a background horizontal diffusivity that mixes diapycnally.

(2) Implement Visbeck et al.'s formulation of spatially varying diffusivities as an alternative to the current formulation based on the Held and Larichev timescale and the Rossby radius as a lengthscale (done).

(3) Add a slope limiting algorithm (mixed-layer depth is sensitive to the slope limiting that is employed) that behaves satisfactorily within and immediately below the mixed layer.

(4) Implementation in the trunk+ NVTK + documentation

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Testing

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

NVTK Tested	'''YES/NO'''
Other model configurations	'''YES/NO'''
Processor configurations tested	[ Enter processor configs tested here ]
If adding new functionality please confirm that the New code doesn't change results when it is switched off and ''works'' when switched on	'''YES/NO/NA'''

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

'Please add further summary details here'

• Processor configurations tested
• etc----

Bit Comparability

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

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

• Which routine(s) are causing the difference?
• Why the changes are not protected by a logical switch or new section-version
• What is needed to achieve regression with the previous model release (e.g. a regression branch, hand-edits etc). If this is not possible, explain why not.
• What do you expect to see occur in the test harness jobs?
• Which diagnostics have you altered and why have they changed?Please add details here........

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System Changes

Does your change alter namelists?	'''YES/NO '''
Does your change require a change in compiler options?	'''YES/NO '''

If any of these apply, please document the changes required here.......

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Resources

''Please ''summarize'' any changes in runtime or memory use caused by this change......''

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IPR issues

Has the code been wholly (100%) produced by NEMO developers staff working exclusively on NEMO?

'''YES/ NO '''

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..........