Dear Tuomas,
Thanks for explaining your proposals further. Please see below for my comments on each of your points.
> On the question about "ocean" or "of_sea_water" specifications, all
> these three variables vary on small scales, so thus "of_sea_water" would
> seem more appropriate. As these variables are related to same processes
> it would seem logical to use the same "of_sea_water" specifier in all of
> them, if that is required.
OK, "of_sea_water" is fine. We need it because we need to be clear about the medium to which each standard name applies, particularly with names that could easily have "in_air" equivalents.
> 1. For the kinetic energy, in contrast to my initial suggestion, it
> seems that "turbulent kinetic energy" would be more appropriate name for
> this variable (it's related to 3D fluctuations, so "vertical" attribute
> doesn't seem fit). I agree about the "specific" keyword. Would something
> like "specific_turbulent_kinetic_energy_of_sea_water (m2 s-2)" be
> possible?
Yes, I think your suggested name is fine. Although we have names for turbulent_deposition in air we don't currently have any explanatory text for the term "turbulent" and I think it would be useful to include something in the definitions both for your proposed names and the existing ones. I suggest the following wording for the definition:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the kinetic energy of all eddy-induced motion that is not resolved on the grid scale of the model.'
Is that OK?
>
> 2. The dissipation rate means the dissipation of the turbulent kinetic
> energy of point 1. Units of (W kg-1) are OK. This is a bulk quantity so
> no "due_to" specifier is needed. Could it be something like
> "specific_turbulent_kinetic_energy_dissipation (W kg-1)"?
>
We need to specify the medium so the whole name would be "specific_turbulent_kinetic_energy_dissipation_in_sea_water" (note "in" rather than "of" in this case because it reads better in English), but otherwise fine. Units of W kg-1 are OK. Borrowing some words from the definitions of existing "dissipation" names I suggest the following:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the kinetic energy of all eddy-induced motion that is not resolved on the grid scale of the model. The dissipation of kinetic energy arises in ocean models as a result of the viscosity of sea water.'
>
> 3. The mixing length is also related to turbulence in the ocean. To me
> "turbulent_mixing_length (m)" would be a natural starting point. This
> mixing length does not have vertical/horizontal orientation and is not
> specific to temperature/salinity for example, so those specifiers are
> not needed.
>
"turbulent_mixing_length" is fine, so the full name would be "turbulent_mixing_length_of_sea_water"; m.
I suggest the following definition:
' "Turbulent mixing length" is used in models to describe the average distance over which a fluid parcel can travel while retaining properties that allow the parcel to be distinguished from its immediate environment.'
In all cases please feel free to improve on my definitions!
Best wishes,
Alison
>
>
> Best regards,
>
> Tuomas Karna
>
> Post-Doctoral Fellow
> Center for Coastal Margin Observation and Prediction (CMOP)
> Oregon Health and Science University
> karnat at stccmop.org
>
> On 02/27/2013 05:50 AM, alison.pamment at stfc.ac.uk wrote:
> > Dear Tuomas,
> >
> > Thanks for your questions.
> >
> > Firstly, I should mention that you appear to be looking at a rather old
> version of the standard name table (version 16). The table is updated
> periodically and the most recently published version can always be
> obtained at
> > http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-
> table/current/cf-standard-name-table.html.
> > However, it may be that the current version of the table still does not
> contain all the quantities you need, in which case new names can be
> proposed on this mailing list.
> >
> > You say that you are happy to use the existing names
> ocean_vertical_momentum_diffusivity (m2 s-1) and
> ocean_vertical_tracer_diffusivity (m2 s-1) for the first two quantities in your
> list. I think new names may well be needed for the other quantities. When
> proposing new names it is always helpful to try to follow as closely as
> possible the syntax of existing names. This also helps when writing the
> definitions of the names.
> >
> > 1. vertical eddy kinetic energy (per unit mass), unit m2 s-2.
> > We already have a name specific_kinetic_energy_of_sea_water (m2 s-2)
> for which the definition simply says ' "specific" means per unit mass.' We
> also have existing names that refer to ocean_eddy_kinetic_energy. Based
> on these, I would suggest adding a new name of
> specific_vertical_eddy_kinetic_energy_of_sea_water (m2 s-2). Also, based
> on the definitions of the existing vertical_X_diffusivity names (where X is
> "momentum" or "tracer") I would suggest a definition along the lines of '
> "specific" means per unit mass. The construction
> "vertical_eddy_kinetic_energy" means the kinetic energy of vertical
> motions which are not resolved on the grid scale of the model.'
> >
> > 2. kinetic energy dissipation rate, unit m2 s-3.
> > There is an existing name
> ocean_kinetic_energy_dissipation_per_unit_area_due_to_vertical_friction
> with units of W m-2 and a corresponding name
> ocean_kinetic_energy_dissipation_per_unit_area_due_to_xy_friction. Your
> quantity is not "per_unit_area" so at first sight we might give it a unit of W =
> kg m2 s-3. However, you need m2 s-3 which is the same as W kg-1 and this
> suggests that we need to add "specific" to the name again. If you want
> energy dissipation arising from all possible processes then we wouldn't
> need the "due_to_process" phrase so the name would be
> ocean_specific_kinetic_energy_dissipation (m2 s-3). However, if you want
> to refer specifically to the vertical component of dissipation perhaps you
> might want to keep the "due_to_vertical_friction" part?
> >
> > 3. mixing length, unit m.
> > We don't currently have any standard names related to this quantity. I
> think the name needs to be more specific because, for example, we could
> have different mixing lengths in atmosphere and ocean. If the mixing length
> varies on a large scale then we would probably call it ocean_mixing_length,
> but if there is a lot of variation on a small scale then the appropriate name
> would be mixing_length_of_sea_water. Also, is the mixing length the same
> horizontally and vertically or is there a need to distinguish between
> lateral/vertical mixing? Is the mixing length the same for all properties such
> as temperature and salinity or do we need to make any distinction? If you
> could explain a bit more about the context in which the name will be used it
> will be easier to decide on the precise wording and also to produce a
> definition.
> >
> > Best wishes,
> > Alison
> >
> > ------
> > Alison Pamment Tel: +44 1235 778065
> > NCAS/British Atmospheric Data Centre Email:alison.pamment at stfc.ac.uk
> > STFC Rutherford Appleton Laboratory
> > R25, 2.22
> > Harwell Oxford, Didcot, OX11 0QX, U.K.
> >
> >> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On
> Behalf Of Tuomas Karna
> >> Sent: 27 February 2013 00:26
> >> To:cf-metadata at cgd.ucar.edu
> >> Subject: [CF-metadata] standard names for ocean model turbulent
> quantities
> >>
> >> Hi All,
> >>
> >> We are currently in the process of migrating SELFE outputs to CF
> compliant netcdf, using the UGRID conventions (http://bit.ly/ugrid_cf).
> >>
> >> I have a question about the standard names for turbulence closures used
> in ocean models.
> >> We have the following fields:
> >>
> >> - vertical eddy viscosity (diffusivity of momentum), unit m2 s-1
> >> - vertical eddy diffusivity of tracers, unit m2 s-1
> >> - vertical eddy kinetic energy (per unit mass), unit m2 s-2
> >> - kinetic energy dissipation rate, unit m2 s-3
> >> - mixing length, unit m
> >>
> >> Looking at the documentation in [1], I guess for the eddy viscosity and
> diffusivity we could use ocean_vertical_momentum_diffusivity and
> >> ocean_vertical_tracer_diffusivity, respectively. But for the other
> variables I haven't found a reference.
> >>
> >> [1]http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-
> name-table/16/cf-standard-name-table.html/
> >>
> >> Would anyone know if standard names exists for these quantities, and if
> so, where they are documented?
> >>
> >>
> >> Best Regards,
> >>
> >> Tuomas Karna
> >> Post-Doctoral Fellow
> >> Center for Coastal Margin Observation and Prediction (CMOP)
> >> Oregon Health and Science University
> >> karnat at stccmop.org
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