2017 Update NEMO Development Strategy document

Last edited 12/08/16 01:43:33 by vancop

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Context and objectives

The NEMO Developer's Committee is responsible for the organisation of an update of NEMO Development Strategy document published in 2014. Objective is to produce a new version of this document in June 2017.
Agenda has been approved 28 June 2016:

  • July to September 2016:
    • Experts identified in the table above to build the preliminary list of questions to discuss (on a wiki page, to be created), and the list of possible contributors
  • September 2016:
    • Comments and additions of these documents by Developer's Committee members
    • Developer's Committee to suggest list of participants for the meeting
  • October 2016: !Agenda and announcement of the meeting in March 2017. (See attached document from J. Le Sommer and M. Bell at the bottom of the page)
  • December 2016: During Developer's Committe meeting, finalize organisation of Development Strategy meeting
  • January to March 2017:Experts listed in table above to draft their chapter
  • March 2017: Development Strategy meeting
  • March to June 2017: Writing and release of new version of Development Strategy document and endorsment from Steering Committee
  • June 2017: Publication of updated NEMO Development Strategy document

Work has been distributed by chapters of the document:

Expert(s) to lead discussions and writing of the chapter
Chapter 1 - Elements of long-term strategy as defined in 2017 → 2022 C. Lévy and writing group
Chapter 2 - Target applications for NEMO by 2022. Julien Le Sommer
Chapter 3 - HPC performance constraints HPC working group
Chapter 4 - Future evolutions of NEMO ocean kernel. Mike Bell
Chapter 5 – Ocean dynamics component of NEMO (including state of the art on subgridscale parametrisations and on tides, see above) Julien Le Sommer
Chapter 6 – Toward locally higher effective resolution: AGRIF Jérôme Chanut
Chapter 7 - The assimilation and ensemble component of NEMO Pierre-Antoine Bouttier and Dan Lea
Chapter 8 - The ice components of NEMO Ed Blockley and Martin Vancoppennolle
Chapter 9 -Air sea interface and surface boundary layer physics Laurent Brodeau
Chapter 10 - The biogeochemical component of NEMO: TOP and its interface Olivier Aumont and Tomas Lovato
Chapter 11 - NEMO validation and range of user support (including user interface to build configurations, and Configuration Manager) Andrew Coward

This page includes a first draft, written by the experts listed above, indentifes for each chapter the points of concensus and the list of subjects to be discussed (with associated list of questions).


Template as starting point for each chapter below:

List of points for which concensus is reached:
(associated actions to schedule, if relevant)

List of subjects in discussion (no concensus yet)
and associated question to lead the discussions next March


Chapter 1 - Elements of long-term strategy as defined in 2017 → 2022 - C. Lévy and writing group

Chapter 2 - Target applications for NEMO by 2022. - Julien Le Sommer

Chapter 3 - HPC performance constraints - HPC Working Group

Please see the attached word document https://forge.ipsl.jussieu.fr/nemo/attachment/wiki/2017UpdateNEMOStrategy/FirstSteps/NEMO_Development_Strategy_HPC_questions.docx

Chapter 4 - Future evolutions of NEMO ocean kernel. - Mike Bell

Chapter 5 – Ocean dynamics component of NEMO (including state of the art on subgridscale parametrisations and on tides, see above) - Julien Le Sommer

Chapter 6 – Toward locally higher effective resolution: AGRIF - Jérôme Chanut

Chapter 7 - The assimilation and ensemble component of NEMO - Pierre-Antoine Bouttier and Dan Lea

  • Establish an identity for the NEMO DA community
    • Create a list of NEMO users working on DA or using the assimilation interface for other purposes (for example model validation compared to observations). This would be held on WG wiki or the NEMO website.
    • Keep the wiki regularly updated
    • Create a NEMO DA mailing list
  • The future of NEMO-TAM and whether and how it is kept up to date with model updates is a question the DA WG will consider. No recommended actions currently. This will be reviewed at future WG meetings.
  • Ensemble mode. There is an increasing interest in the data assimilation community for using ensemble information in data assimilation.
    • Many group members would find a single executable approach useful for running all the ensemble members. This requires an MPI communicator for the sub-domains of each ensemble member and another MPI communicator for passing information between ensemble members.
  • Higher resolution modelling
    • Improve the efficiency of the assimilation interface code (OBS and ASM)
    • Deal correctly with observations which are spread over several model grid cells (i.e. have a "footprint")
  • NEMO-OBS package
    • If the above ensemble mode is introduce the NEMO-OBS package should be updated to produce ensemble diagnostics.
    • Update the central version of the OBS plotting tool (dataplot) to a new python version
    • Develop some community tools for assessing ensembles which can either go into the TOOLS directory or be made available on the WG wiki or NEMO website.

Chapter 8 - The ice components of NEMO - Ed Blockley and Martin Vancoppenolle

There are numerous directions towards which the representation of sea ice could be improved.

A non-exhaustive and perfectible list would include

  • sea ice rheology: Towards improving the representation of deformation scaling laws, landfast ice & ice arches. Available approaches to be discussed include
  • VP-likes vs anisotropic vs elasto-britlle rheologies.
  • Eulerian vs lagrangian approaches
  • ice atmosphere coupling: Towards improving the representation of ice-atmosphere interactions, notably in polynya regions or near the ice edge. This would clearly benefit from new possibilities offered by the interactive boundary layer physics. A new approach of coupling via conduction flux in the ice has been proposed at UKMO.
  • ice thermodynamics: Ice thermodynamics are central because they control the energetic transfer in the sea ice zone. Improvements include better account of
  • mushy layer thermodynamics (salt & heat conservation, frazil ice, platelet ice)
  • snow & surface meltwater (melt ponds) physics
  • radiative transfer (beer law → delta-eddington multiband schemes)
  • ice floe size reperesentation. Ice floe size is absent from current sea ice representations in large-scale models. Yet floe size controls lateral melting and wave-ice coupling. Recent works have explored possible ways of improvements.
  • sea ice biogeochemistry. Sea ice BGC is more of an observational than a modelling problem at the moment. Yet recent studies suggest simple first-order representations of organic matter synthesis in sea ice, carbonate chemistry and carbon fluxes in the sea ice zone.

Experts suggested: D. Feltham (Reading), T. Fichefet (UCL), D. Salas (Meteo France),

Chapter 9 - Air sea interface and surface boundary layer physics - Laurent Brodeau, Gurvan Madec

Please see here!!! Can't cope with this wiki syntax…

Chapter 10 - The biogeochemical component of NEMO: TOP and its interface - Olivier Aumont and Tomas Lovato

  • Establish the production of scientifically validated simulations (e.g., validation suite and data repository) to enable the long term assessment of model developments and improvements.
  • The medium term development of TOP should lead to a general interface for ocean tracers

capable to solve all key processes (BC treatment, light in the water column, sinking etc), independently from a specific biogeochemical model. This will translate into a seamless interface where only the core equations of biogeochemical models will be needed to couple with NEMO.

  • The uprising complexity of biogeochemical models will require the revision of current HPC approach and the adoption of novel techniques to cope with the increasing computational efforts. In particular, the exploitation of accelerators and GPUs might become a key resource to deal with computational constraints.

Chapter 11 - NEMO validation and range of user support (including user interface to build configurations, and Configuration Manager) - Andrew Coward

  • A clean-up of the configuration set-up routines in NEMO is seen as an essential simplification. This has been started in 2016 and will continue. This process puts greater responsibility on a configuration developer to provide either external input files or user-defined code modules. The system team will endeavour to provide sufficient examples and tools to ease this burden. The benefits are a simpler code kernel which is more suitable for adaptation to future architectures and, ultimately, a less error-prone route to setting up new configurations. Examples and methods need to be well documented and these guides need to be readily available to ease the transition.
  • The new interface eases the task of providing simple test cases and the range of such options is expected to grow rapidly. Test cases should be viewed separately to reference configurations but they are useful for demonstrating and comparing numerical schemes; especially when analytical solutions exist for comparison.
  • XIOS-2 should be adopted as default but this still lacks documentation targeted towards NEMO users. The system team should consider compiling an 'XIOS in NEMO' guide detailing relevant settings and tricks for obtaining some of the more complex outputs. Mostly this is a case of documenting the work done to obtain CMIP6 diagnostics.
  • A basic but well-tested Configuration Manager (SIREN) is now part of the system. These tools allow a regional sub-model of any ORCA grid to be set up easily. Users will expect such tools for setting up regional models with open boundaries (BDY) and for AGRIF nests; ideally the same tool should be used for both. The UK has made some progress with Python-based tools for constructing regional sub-models from any gridded input. This effort has currently stalled but is expected to restart next year. The aim should remain to provide a single set of tools for regional model configuration.
Last modified 4 years ago Last modified on 2016-12-08T01:43:33+01:00

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