Dear Allison,
Thank you for your comments. I'd propose some further changes to the
definitions:
1. "specific_turbulent_kinetic_energy_of_sea_water (m2 s-2)"
As turbulent kinetic energy is not necessary equivalent to model's
subgrid scale eddy kinetic energy, I'd formulate the definition as:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the
kinetic energy of small scale turbulent fluctuations of the flow. '
2. "specific_turbulent_kinetic_energy_dissipation_in_sea_water (W kg-1)"
The definition would then become:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the
kinetic energy of small scale turbulent fluctuations of the flow. The
dissipation of kinetic energy arises in ocean models as a result of the
viscosity of sea water.'
3. "turbulent_mixing_length_of_sea_water (m)"
' "Turbulent mixing length" is used in models to describe the macro
length scale of energy-containing eddies in a turbulent flow. '
If these definitions seems too vague, I can try to elaborate them futher.
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 03/07/2013 06:34 AM, alison.pamment at stfc.ac.uk wrote:
> 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
Received on Fri Mar 15 2013 - 10:50:18 GMT
