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Working group leader (and responsible for wiki pages): Frédéric Dupont

Members of the working group

• Susan Allen (UBC, Canada)
• Mike Bell (UKmet)
• Natacha Bernier (Environnement Canada)
• David M. Byrne (NOC)
• Loren Carrere (CLS)
• Jérôme Chanut (Mercator Océan)
• Andrew C. Coward (NOC)
• Frédéric Dupont (Environnement Canada)
• Ariane Koch-Larrouy (LEGOS)
• Julien Le Sommer (Grenoble)
• Youyu Lu (DFO, Canada)
• Florent Lyard (LEGOS)
• Yves Morel (LEGOS)
• Jean-Philippe Paquin (Environnement Canada)
• Jeffrey Polton (NOC)
• Chris Wilson (NOC)
• Simon Mueller (NOC)
• Enda Odea (UKmet)
• Pengcheng Wang (Environnement Canada)

Objectives

Sustain and improve Tides implementation in NEMO.
Provide support to users.

WG internal meetings

• 2020-11-19: introductory meeting and quick round table. Examples of issues that were discussed: data assimilation (or correction methods), wet-and-drying, diagnostic tools, new tidal astronomical potential, numerical issues, OBC. A conclusion was to organize next a special meeting about data assimilation (or correction methods) and afterwards another about common tools and numerics.
• 2021-01-12: presentation of two methods for assimilating/correcting the tides.
  • Tidal Nudging in the momentum equations and S2 issues in tidal-only runs presented by Pengcheng Wang, who confirmed afterwards that he is nudging to the tidal atlas transport (U*H).
  • Correction method for implementing tides in (coarse) OGCMs presented by Yves Morel, also referred as the "injection" approach.
• 2021-02-16:
  • Presentation of the incoming improvement to tides in NEMO by Simon Mueller, discussion if some tidal parameters should be variable across all constituents.
  • Energy diagnostics
  • Discussion on boundary conditions, limitation of Flather OBC close to the resonant latitude, need for a 'clamped' SSH boundary.
  • Discussion on normal modes and the difficulty of adding an eigenvalue library into NEMO.
  • Discussion on internal wave drag parameterization.
  • Discussion around a newly proposed astronomical potential based solely on astronomical arguments. pros: it does not require the development for different constituents; cons: difficulty of separating constituents.
• 2021-03-30: Due to the small attendance (Easter Holiday was starting in some areas), we decided to postpone discussions to 2021-04-15
• 2021-04-15: paper review
  • https://www.sciencedirect.com/science/article/pii/S0021999119305662 better captures the barotropic energy using vertical mode decomposition and argue for a different temporal scheme for the time-splitting barotropic mode
  • https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2003JC002034 discusses the SAL term starting from a Green function (the full approach) to simplified approach (a linearized approach where SAL is proportional to the local pressure).
• 2021-04-27: general discussion
  • advection of turbulence fields (not planned in NEMO)
  • internal wave and bottom layer dissipation: we do not have a good parameterization for those. Wave drag only addresses the barotropic to barotropic energy conversion which is then locally dissipated.
  • Ariane and Jérôme reviewed some COMMODO test cases: impact of time filter and implicit/explicit numerical diffusion due to the advection scheme.
  • Youyu Lu commented on his [attachment:Lu_2001-JTECH.pdf 2001 paper] which compared model and semi-analytical results
  • the self-advection of the depth-averaged velocity used in the time-splitting scheme seems to be in the plan
  • Jérôme discussed a recent development: use of penalizing method (porosity/permeability) for representation of the water intersecting the bottom.
• 2021-05-27: discussion about tools for tides, two schools of thoughts, not necessarily exclude:
  • offline scripts for quick diagnostics, some presumably existing (harmonic analyses, vertical mode separation, quick energy flux calculation).
  • inline calculations for rigorous diagnostics
  • offline internal mode decomposition requires a pressure output that is not coded in XIOS/NEMO at the moment, inline would require a link to a eigenvalue library
  • existing scripts in UK for creating configurations (including extraction of tidal components from a tidal atlas?)
  • identifying existing tools could provide a pragmatic contribution of this group to the NEMO community.
• 2021-12-01:
  • review of the NEMO Strategy chapter.
  • common tools: Jeff and Crhis provided some links to some basic validation and diagnostic tools available at https://british-oceanographic-data-centre.github.io/COAsT/docs/examples/tidegauge and https://british-oceanographic-data-centre.github.io/COAsT/docs/examples/stratification respectively. Chris will look into the vertical mode decomposition.
  • SAL term: we found out that the spatially-varying coefficient of Stepanov and Hughes (2004) was used in Pengcheng's paper https://www.sciencedirect.com/science/article/pii/S1463500321001463, discussion about how to score the accuracy (and cost) of this approach against the typical SAL FES forcing or the full Green function convolution. Maybe next year?
  • internal wave drag for the barotropic mode: the Jayne and St. Laurent (2001) [https://doi.org/10.1029/2000GL012044] method was also used in Pengcheng's paper and in one of David's NEMO configurations. No other experts present to discuss other parametrization. Would also require a quantitative assessment. Chris raises concerns that the TMX module in NEMO might double-counts conversion of energy to internal wave dissipation since the input fields comes from a barotropic model whereas NEMO might resolve some of the internal wave spectra. There could a need for having the internal wave drag seen by the barotropic mode in TMX.
• 2022-07-13:
  • feedback from the Nemo Strategy Development presentation and reviews
  • discussion with our special guess, Brian Arbic on internal wave drag. Brian gave us a thorough review on it: is it needed, do you need to filter the velocity in order to add a drag on the tides only? Need to check the level of internal dissipation in the vertical as well, need to resolve the bottom layer
  • Brian also covered our second planned implementation in NEMO, the SAL term. He mentioned that spherical harmonic calculation were getting better (Schindelegger et al., 2018, https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JC013959). Chris reported on their own effort at NOC to improve the calculation.
• table for NDS planning: https://docs.google.com/spreadsheets/d/1Gww7slhF6Li4a68C4z5yzUDSlDfeZvGE16whS_T3jyk/edit?usp=sharing