NEMO Developer's Committee meeting Minutes

The meeting took place by videoconference on Monday 9 November 2020

Participants:

• Chairperson: Mike Bell
• External experts: Jean-Marc Molines, Joana Staneva, David Marshall, Oleksandr (Sasha) Huziy (representing F. Dupont)
• Consortium Experts : Momme Buttenschon, Pier Guisepe Fogli, Julien Le Sommer
• NEMO Officers: Amy Young (MetO), Sébastien Masson (CNRS), Dorotea Iovinno (CMCC), Guillaume Samson (MOI)
• Working groups leaders: Ed Blockley, Italo Epicoco, Jérôme Chanut, Sébastien Masson, Tomas Lovato, Dan Lea
• NEMO Project manager: Claire Lévy
• Permanent Invitees (System Team members and other developers with an action in the work plan): Emanuela Clementi, Gurvan Madec, Miguel Castrillo, Romain Bourdalle-Badie, Sibylle Techene, Yevgeny Askenov, Clément Rousset, Clément Bricaud, Diego Bruciaferri
• Others: Miguel Castillo, Lorenzo O'Next, Maicon Faria,

Absentees:

• Consortium Experts: H. Hewitt, R. Benshila, J. Hirschi, G. Nurser, G. Garric
• WG leaders: O. Aumont, M. Vancoppenolle,
• External Experts: P. Oddo, L. Brodeau,
• NEMO Officers: A. Coward

Purpose of meeting: for each WG to review progress against the NDS and discuss successes and issues

Actions from previous meeting​

Actions 2-4 have been done. Action 1 is replaced by:

Action 1: Ed B, Clement R & Martin V to discuss issues arising from the development of sea-ice functionality at v4.0.3 that need to be transferred into the trunk and discuss with Seb if they cannot be resolved.

Review of WGs

• HPC (Italo)​

The HPC WG is a relatively large, well funded and active group. It is making good progress on all the actions identified in the NDS. Some performance issues involve a lot of investigation and some solutions being relatively intrusive take a long time to develop (e.g. tiling, mixed precision, porting to GPUs). The latter need to be carefully evaluated before they are accepted into the code to ensure that they are sustainable in the long-term and that proper information/instructions are provided on the implications for NEMO code maintenance.

• Kernel (Mike)​

Good progress is being made on the transition to the RK3 time-step scheme. A sub-group to analyse the options for more general vertical coordinates (e.g. V-ALE) has just started up.

The NDS 2018-202 stated that NEMO will rely on AGRIF to provide a multi-resolution capability. We need to keep a watching brief on MPAS-Ocean and FESOM2 that are developing rapidly. One could not introduce an unstructured grid into NEMO. If one did it would be a different model. It would be hugely disruptive if it was decided to transition to an unstructured grid model.

• LeSommer_Chapter-5-Ocean-Dynamics_NDC_2020-11-09_v2.pdf​ Dynamics (Julien)

A sub-group led by Fred Dupont has shown that tides can be quite well represented by NEMO. The sub-group on parametrisation of unresolved mesoscale motions is yet to start work. There has been progress gathering idealised test cases that evaluate the representation of specific processes within a github repository and some progress on the tracer and momentum trend diagnostics. The NDC can endorse project proposals that are in line with the NDS but it has not been asked to do so, so it seems this may not be generally recognised.

Julien is discussing with Julie Deshayes whether she could help lead this WG.

• AGRIF (Jerome)​

The AGRIF WG is focused on the team of active developers. This team works well and has made good progress with CMEMS and IMMERSE funding.

Jerome highlighted different levels of ambition for AGRIF with NEMO: 1) a tool for regional modelling; 2) a tool for multi-resolution capability; 3) a tool for efficient use of HPCs. He also suggested ideas for how the best capabilities of OASIS and AGRIF could be used together. The level of ambition that the consortium aims to support needs to be clarified.

Mike suggested that Jerome discuss his ideas for grand-mother grids (coarsening) with Eric Maisonnave and asked Jerome to consider holding an AGRIF user workshop at some appropriate time.

• Observation interface​ (Dan)

This WG is focused on the observation operator (OBS) and incremental assimilation update (ASM) modules. It has made good progress in improving these codes. Including configurations that call these modules in the SETTE tests has improved the code maintenance. These modules are used by the Met Office and ECMWF but not by MOI or CMCC and their use by the scientific community is very limited. The WG is interested in extending the stochastic parametrisation in NEMO and using ensembles of NEMO integrations. Julien and Dan will discuss these topics. Dan and Tomas will discuss whether the OBS operator could be extended to BGC information.

Presentations and discussions postponed to later a meeting

• Sea-ice​ (Ed)
• Air-sea interaction​ (Seb)
• TOP-WG_Lovato_NDC2020.pdf​ TOP (Tomas)
• Verification (Mike)​

Representation and membership of NDC (Mike)​ (10-15 minutes)

Discussions have shown that these roles, although they have been defined for quite a while (see https://forge.ipsl.jussieu.fr/nemo/attachment/wiki/ScientificAdvisoryBoard/MembersOfCommittees.update2020.pdf so as the documents of previous years) are not clearly perceived by the NDC members.

This point and the suggestions should be discussed further and finalised during next meeting in December.

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