Dear Stephen,
Thanks for your comments regarding the ocean/sea_water question. During
our telephone conversation we agreed that I should forward your comments
to the mailing list, which I have done at the end of this message.
During the conversation, we discussed whether a number of standard names
in the table, for example, ocean diffusivities, transports and
overturning, should in fact use the term 'sea_water' instead of 'ocean'
because these quantities can in general vary with location. We agreed
that 'ocean' can be an ambiguous term because it is not obvious whether
it refers only to sea water or also to sea ice. Furthermore, we agreed
that for the present the name sea_water_mass_per_unit_area would be
added to the table.
Additionally, we agreed that I would raise the question of 'ocean'
versus 'sea_water' again on the mailing list during April to allow a
review of all existing names that use either term. Aliases would be
created for any names that need to be changed. This discussion can take
place separately from any specific set of standard name proposals and
free from the constraints of the CMIP5 timetable.
Best wishes,
Alison
> -----Original Message-----
> From: Stephen Griffies [mailto:Stephen.Griffies at noaa.gov]
> Sent: 11 February 2009 21:28
> To: Pamment, JA (Alison)
> Cc: Jonathan Gregory; Stephen Griffies
> Subject: Re: [CF-metadata] new named fields for ocean
>
> Alison,
>
> Many thanks for your careful summary of the issues for the ocean
> variables proposed. I am pleased that you have accepted the majority
> of
> the fields. I have one concern, however, expressed below...
>
>
> Pamment, JA (Alison) wrote:
> >
> > This raises a subtle point. The direct analogy of
> > atmosphere_mass_per_unit_area would actually be
> ocean_mass_per_unit_area
> > because both would then refer to the large-scale body, rather than a
> > local property of the medium. In standard names we make a
> distinction
> > between the terms 'atmosphere' and 'in_air' and similarly between
> > 'ocean' and 'sea_water'. Thus we talk about the ocean mixed layer
> but
> > the velocity of sea water. Karl's point about the order of the
> wording
> > is also a fair one. I think the choice is between
> > ocean_mass_per_unit_area or sea_water_mass_per_unit_area and we
> should
> > probably choose the former to be consistent with the atmosphere
name.
> > What do others think?
> >
> > N.B. If we opt for ocean_mass_per_unit_area then for consistency I
> think
> > we should also change proposal 2.1, sea_water_mass, to ocean_mass
> (kg).
>
>
> In summary, I read the proposal to change
>
> "sea_water_mass_per_unit_area" and "sea_water_mass" (perhaps
> "sea_water_volume" as well?)
>
> to
>
> "ocean_mass_per_unit_area" and "ocean_water_mass" (and
> "ocean_water_volume"?)
>
> I am confused about the convention for names. Let me note an example
in
> the CMIP5 report that prompts my confusion. In Table 2.3 please find
> the
> names "sea_water_x_velocity" as well as "ocean_mass_x_transport".
> These
> two fields are related by the equation
>
> ocean_mass_x_transport = density*dy*dz*sea_water_x_velocity
>
> where density=ocean density, dy*dz is the cross-sectional area of a
> zonal grid face. Both fields are 3d local fields measured for a
single
> grid box in the liquid ocean. So how would the convention apply for
> these two fields? Is there a problem, and you did not notice the
> problem? Or is the convention properly applied, and I am
> misunderstanding the convention?
>
> There other such examples, where the preface "ocean" is used for a
> local
> 3d field, not determined by any "global" criteria (e.g., Tables 2.3,
> 2.9
> and 2.10).
>
>
> > There are already six ocean_mixed_layer_thickness names, as follows:
> > ocean_mixed_layer_thickness
> > ocean_mixed_layer_thickness_defined_by_mixing_scheme
> > ocean_mixed_layer_thickness_defined_by_sigma_t
> > ocean_mixed_layer_thickness_defined_by_sigma_theta
> > ocean_mixed_layer_thickness_defined_by_temperature
> > ocean_mixed_layer_thickness_defined_by_vertical_tracer_diffusivity
> >
> > As you will see, this list includes the newly proposed name -
> apologies
> > for not having spotted it before! The definition of
> > ocean_mixed_layer_thickness_defined_by_mixing_scheme is "The ocean
> mixed
> > layer is the upper part of the ocean, regarded as being well-mixed.
> The
> > base of the mixed layer defined by the mixing scheme is a diagnostic
> of
> > ocean models." The definition of ocean_mixed_layer_thickness is
"The
> > ocean mixed layer is the upper part of the ocean, regarded as being
> > well-mixed. Various criteria are used to define the mixed layer;
this
> > can be specified by using a standard name of
> > ocean_mixed_layer_defined_byX." I wonder if in practice these two
> are
> > really the same quantity, as Karl suggests. If so, I would suggest
> > retaining the name ocean_mixed_layer_thickness and making
> > ocean_mixed_layer_thickness_defined_by_mixing_scheme an alias of it.
> > Can anyone comment on whether these names describe distinct
> quantities?
>
> As noted by the plethora of names, there are many ways to define the
> ocean mixed layer. These methods lead to subtly distinct results, and
> some studies prefer one method over the other. I could go into
> details,
> but prefer to simply make the recommendation that we keep the names
> distinct, and thus NOT make any aliases.
>
>
> Best,
> Stephen Griffies
>
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
Rutherford Appleton Laboratory Email: alison.pamment at stfc.ac.uk
Chilton, Didcot, OX11 0QX, U.K.
--
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Received on Mon Mar 30 2009 - 05:51:20 BST
