Dear Alison,
Thank you for your reply.
I was indeed looking at older version of the standard, thanks for
pointing that out. My comments below.
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?
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)"?
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.
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.
Best regards,
Tuomas Karna
Post-Doctoral Fellow
Center for Coastal Margin Observation and Prediction (CMOP)
Oregon Health and Science University
[email protected]
On 02/27/2013 05:50 AM, [email protected] 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:[email protected]
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
From: CF-metadata [mailto:[email protected]] On Behalf Of Tuomas
Karna
Sent: 27 February 2013 00:26
To:[email protected]
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
[email protected]
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