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= '''Tides WG''' =
Last edition: '''[[Wikinfo(changed_ts)]]''' by '''[[Wikinfo(changed_by)]]'''

'''!!!! CONNECTION INFO!!!! '''

https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZTNmNmRjMTctNTg5Ni00ODI4LWIzYTktNTBiMmNiYmNkODQ3%40thread.v2/0?context=%7b%22Tid%22%3a%22740c5fd3-6e8b-4176-9cc9-454dbe4e62c4%22%2c%22Oid%22%3a%22c7a3bcfc-004c-4992-9565-406f7d7bc80f%22%7d

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: ==
[[TOC(noheading,WorkingGroups/Tides/*, depth=2)]] [[TitleIndex(WorkingGroups/Tides/, hideprefix)]]

 * 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. [attachment:NEMO_tides_WG_20201119.ppt introductory material]
 * 2021-01-12: presentation of two methods for assmilating/correcting the tides.
  * [attachment:nemo-tide_WG_20210112_Nudging_PWang.pdf 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).
  * [attachment:nemo-tide_WG_20210112_TCorrection_YMorel.pdf 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  [attachment:2021-02-16_NEMO_WG_Tides_NEMO_v4_2_Mueller.pdf slides], 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.