I agree, but just wanted to chime in that I appreciate that the definitions
spell out the meanings of these terms.
- Nan
On 4/26/18 10:59 AM, Lowry, Roy K. wrote:
>
> Dear Evan,
>
>
> To an oceanographer, the term?'sigma-theta' is as well-known as
> 'temperature' and the Standard Names include 'sea_water' to
> give?context. Also, sigma-theta (and sigma-t) are used in existing
> Standard Names.
>
>
> Avoiding sigma-theta would need something very verbose like 'density
> difference between sea water and pure water computed at
> sample?potential temperature', which is both ugly and invisible to an
> oceanographer's data searches.
>
>
> Cheers, Roy
>
>
> ------------------------------------------------------------------------
> *From:* CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of
> Manning, Evan M (398B) <Evan.M.Manning at jpl.nasa.gov>
> *Sent:* 26 April 2018 15:25
> *Subject:* Re: [CF-metadata] how to use
> ocean_mixed_layer_thickness_defined_by_*
> It?s outside of my area so I don?t have an alternative to offer, but
> it is bad practice to use the names of Greek letters in standard
> names.? Though I?m sure the meaning in context is clear to members of
> the community, these letters have different meanings in different
> contexts.
>
>
> ? -- Evan
>
> On 4/26/18, 6:04 AM, "Alison Pamment - UKRI STFC"
> <alison.pamment at stfc.ac.uk> wrote:
>
> ??? Dear Sebastien,
>
> ??? Thank you for your proposals for three new standard names for
> coordinate variables that will be used to describe ocean mixed layer
> thickness according to various physical criteria. Thank you also to
> Jonathan and Roy for their suggestions.
>
> ??? I agree with the need for these names. I agree also with
> Jonathan's approach of keeping the definitions of the new names
> general while referring to the coordinate variables in the definitions
> of the existing mixed_layer_thickness names.
>
> ??? The new names would then be as follows:
>
> ??? sea_water_temperature_difference (K)
> ??? 'Sea water temperature is the in situ temperature of the sea water.'
>
> ??? sea_water_sigma_theta_difference (kg m-3)
> ??? 'Sigma-theta of sea water is the potential density (i.e. the
> density when moved adiabatically to a reference pressure) of water
> having the same temperature and salinity, minus 1000 kg m-3.'
>
> ??? sea_water_sigma_t_difference (kg m-3)
> ??? 'Sigma-t of sea water is the density of water at atmospheric
> pressure (i.e. the surface) having the same temperature and salinity,
> minus 1000 kg m-3.'
>
> ??? These three names are accepted for publication and will be added
> in the May update of the standard name table.
>
> ??? In addition the definitions of the mixed_layer_thickness names
> would be amended as follows:
>
> ??? ocean_mixed_layer_thickness_defined_by_temperature (m)
> ??? 'The ocean mixed layer is the upper part of the ocean, regarded as
> being well-mixed. The base of the mixed layer defined by temperature,
> sigma or sigma_theta is the level at which the quantity indicated
> differs from its surface value by a certain amount. A coordinate
> variable or scalar coordinate variable with standard name
> sea_water_temperature_difference can be used to specify the
> temperature criterion that determines the layer thickness.'
>
> ??? ocean_mixed_layer_thickness_defined_by_sigma_t (m)
> ??? 'The ocean mixed layer is the upper part of the ocean, regarded as
> being well-mixed. The base of the mixed layer defined by temperature,
> sigma or sigma_theta is the level at which the quantity indicated
> differs from its surface value by a certain amount. A coordinate
> variable or scalar coordinate variable with standard name
> sea_water_sigma_t_difference can be used to specify the sigma_t
> criterion that determines the layer thickness.'
>
> ??? ocean_mixed_layer_thickness_defined_by_sigma_theta (m)
> ??? ' The ocean mixed layer is the upper part of the ocean, regarded
> as being well-mixed. The base of the mixed layer defined by
> temperature, sigma or sigma_theta is the level at which the quantity
> indicated differs from its surface value by a certain amount. A
> coordinate variable or scalar coordinate variable with standard name
> sea_water_sigma_theta_difference can be used to specify the
> sigma_theta criterion that determines the layer thickness.'
>
> ??? These changes are also accepted and will be published in the May
> standard names update.
>
> ??? Best wishes,
> ??? Alison
>
> ??? -----Original Message-----
> ??? From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On
> Behalf Of Sebastien Villaume
> ??? Sent: 13 April 2018 16:07
> ??? Subject: Re: [CF-metadata] how to use
> ocean_mixed_layer_thickness_defined_by_*
>
> ??? Dear list,
>
> ??? any more comments? can we move forward and agree on these new
> standard names?
>
> ??? thanks
> ??? /S?bastien
>
> ??? ----- Original Message -----
> ??? > From: "Jonathan Gregory" <jonathan.gregory at ncas.ac.uk>
> ??? > Sent: Wednesday, 11 April, 2018 18:32:30
> ??? > Subject: [CF-metadata] how to use
> ??? > ocean_mixed_layer_thickness_defined_by_*
>
> ??? > Dear Sebastien
> ??? >
> ??? > I would favour your alternative
> ??? >> Alternatively, we could move the last sentence of each
> description to
> ??? >> the respective "ocean_mixed_layer_thickness_defined_by_*" standard
> ??? >> names to make that specific usage more explicit. We then keep a
> more
> ??? >> general description for the new "*_difference" standard names.
> ??? > for the reason you give, which appeals to me.
> ??? >
> ??? > Also, instead of "auxiliary coordinate" I would say "coordinate
> ??? > variable or scalar coordinate variable". A scalar coord var is
> ??? > formally like a size-one auxiliary coord var. However the threshold
> ??? > variable could in principle be multi-valued; then you'd have a
> ??? > dimension for it, and it wouldn't be an aux coord var.
> ??? >
> ??? > Best wishes
> ??? >
> ??? > Jonathan
> ??? >
> ??? >
> ??? > ----- Forwarded message from Sebastien Villaume
> ??? > <sebastien.villaume at ecmwf.int>
> ??? > -----
> ??? >
> ??? >> Date: Tue, 10 Apr 2018 10:36:21 +0000 (GMT-00:00)
> ??? >> From: Sebastien Villaume <sebastien.villaume at ecmwf.int>
> ??? >> Subject: Re: [CF-metadata] how touse
> ??? >> ocean_mixed_layer_thickness_defined_by_*
> ??? >>
> ??? >> Dear CF list,
> ??? >>
> ??? >> I took a bit longer to write down the proposed definitions of
> these 3
> ??? >> standard names.
> ??? >>
> ??? >>
> ??? >> standard name: sea_water_temperature_difference
> ??? >> units: K
> ??? >> description:
> ??? >> Sea water temperature is the in situ temperature of the sea water.
> ??? >> The standard name "sea_water_temperature_difference" can be
> used (as
> ??? >> an auxiliary
> ??? >> coordinate) together with the standard name
> ??? >> "ocean_mixed_layer_thickness_defined_by_temperature" to define its
> ??? >> temperature criterion.
> ??? >>
> ??? >>
> ??? >> standard name: sea_water_sigma_theta_difference
> ??? >> units: kg/m3
> ??? >> description:
> ??? >> Sigma-theta of sea water is the potential density (i.e. the
> density
> ??? >> when moved adiabatically to a reference pressure) of water
> having the
> ??? >> same temperature and salinity, minus 1000 kg m-3. The standard
> name
> ??? >> "sea_water_sigma_theta_difference" can be used (as an auxiliary
> ??? >> coordinate) together with the standard name
> ??? >> "ocean_mixed_layer_thickness_defined_by_sigma_theta" to define its
> ??? >> sigma_theta criterion.
> ??? >>
> ??? >> standard name: sea_water_sigma_t_difference
> ??? >> units: kg/m3
> ??? >> description:
> ??? >> Sigma-t of sea water is the density of water at atmospheric
> pressure
> ??? >> (i.e. the
> ??? >> surface) having the same temperature and salinity, minus 1000
> kg m-3.
> ??? >> The standard name "sea_water_sigma_t_difference" can be used
> (as an
> ??? >> auxiliary
> ??? >> coordinate) together with the standard name
> ??? >> "ocean_mixed_layer_thickness_defined_by_sigma_t" to define its
> ??? >> sigma_t criterion.
> ??? >>
> ??? >>
> ??? >> Alternatively, we could move the last sentence of each
> description to
> ??? >> the respective "ocean_mixed_layer_thickness_defined_by_*" standard
> ??? >> names to make that specific usage more explicit. We then keep a
> more
> ??? >> general description for the new "*_difference" standard names.
> ??? >>
> ??? >> /S?bastien
> ??? >>
> ??? >> ----- Original Message -----
> ??? >> > From: "Jonathan Gregory" <j.m.gregory at reading.ac.uk>
> ??? >> > Sent: Friday, 6 April, 2018 14:24:18
> ??? >> > Subject: Re: [CF-metadata] how touse
> ??? >> > ocean_mixed_layer_thickness_defined_by_*
> ??? >>
> ??? >> > Dear Sebastien and Roy
> ??? >> >
> ??? >> > Thanks. I agree that it's a good idea to include sea_water_.
> ??? >> >
> ??? >> > Best wishes
> ??? >> >
> ??? >> > Jonathan
> ??? >> >
> ??? >> > On Thu, Apr 05, 2018 at 07:04:26PM +0000, Sebastien Villaume
> wrote:
> ??? >> >> Date: Thu, 5 Apr 2018 19:04:26 +0000 (GMT-00:00)
> ??? >> >> From: Sebastien Villaume <sebastien.villaume at ecmwf.int>
> ??? >> >> Subject: Re: [CF-metadata] how touse
> ??? >> >> ocean_mixed_layer_thickness_defined_by_*
> ??? >> >>
> ??? >> >> Dear Jonathan and Roy,
> ??? >> >>
> ??? >> >> thank you for your suggestions.
> ??? >> >>
> ??? >> >> I am happy to go with a set of general standard names if it is
> ??? >> >> fine with everyone. I find it actually useful to make the
> standard
> ??? >> >> names reusable by not hard-coding one of the reference. It is
> ??? >> >> pretty clear from the mixed layer definition that it is a
> difference with respect to the sea surface.
> ??? >> >>
> ??? >> >> I am also happy to prefix sigma_theta and sigma_t with
> sea_water:
> ??? >> >>
> ??? >> >> sea_water_temperature_difference (K)
> ??? >> >> sea_water_sigma_theta_difference (kg/m3)
> ??? >> >> sea_water_sigma_t_difference (kg/m3)
> ??? >> >>
> ??? >> >> I will draft some definitions for tomorrow.
> ??? >> >>
> ??? >> >> thanks!
> ??? >> >>
> ??? >> >> /S?bastien
> ??? >> >>
> ??? >> >> ----- Original Message -----
> ??? >> >> > From: "Lowry, Roy K." <rkl at bodc.ac.uk>
> ??? >> >> > Sent: Thursday, 5 April, 2018 18:34:48
> ??? >> >> > Subject: Re: [CF-metadata] how
> ??? >> >> > touseocean_mixed_layer_thickness_defined_by_*
> ??? >> >>
> ??? >> >> > Dear Jonathan and Sebastien,
> ??? >> >> >
> ??? >> >> > I was initially thinking of not including '
> ??? >> >> > _defining_mixed_layer' in my suggestion and am certainly
> happy
> ??? >> >> > with leaving it out. However, I still think sigma_t and
> sigma_theta should be prefixed with 'sea_water'. This would give:
> ??? >> >> >
> ??? >> >> > sea_water_temperature_difference
> ??? >> >> > sea_water_sigma_theta_difference sea_water_sigma_t_difference
> ??? >> >> >
> ??? >> >> > Cheers, Roy.
> ??? >> >> >
> ??? >> >> > From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on
> behalf
> ??? >> >> > of Jonathan Gregory <j.m.gregory at reading.ac.uk>
> ??? >> >> > Sent: 05 April 2018 18:28
> ??? >> >> > Subject: Re: [CF-metadata] how to use
> ??? >> >> > ocean_mixed_layer_thickness_defined_by_*
> ??? >> >> > Dear Sebastien
> ??? >> >> >
> ??? >> >> > It's interesting that this question hasn't been raised
> before.
> ??? >> >> > Thanks for doing so now. I agree that new standard names
> would
> ??? >> >> > be appropriate. There are already some standard names
> containing
> ??? >> >> > "difference" in various ways. I would suggest that for your
> ??? >> >> > purpose the names don't have to be so specific. You could use
> ??? >> >> > sea_water_temperature_difference sigma_theta_difference
> ??? >> >> > sigma_t_difference because in the context of your use of
> them it
> ??? >> >> > is obvious what difference you mean. That would make these
> names
> ??? >> >> > perhaps useful for other purposes too. This is like the
> rather
> ??? >> >> > generic name air_temperature_threshold which doesn't indicate
> ??? >> >> > what the threshold can be used for. I would also suggest that
> ??? >> >> > the definitions of the three kinds of mixed layer depth
> should
> ??? >> >> > have a sentence added to say that the threshold should be
> stored
> ??? >> >> > in a coordinate var, e.g. like the sentence for
> number_of_days_with_air_temperature_above_threshold.
> ??? >> >> >
> ??? >> >> > Best wishes
> ??? >> >> >
> ??? >> >> > Jonathan
> ??? >> >> >
> ??? >> >> > ----- Forwarded message from Sebastien Villaume
> ??? >> >> > <sebastien.villaume at ecmwf.int>
> ??? >> >> > -----
> ??? >> >> >
> ??? >> >> >> Date: Thu, 5 Apr 2018 13:55:50 +0000
> ??? >> >> >> From: Sebastien Villaume <sebastien.villaume at ecmwf.int>
> ??? >> >> >> Subject: Re: [CF-metadata] how to use
> ??? >> >> >> ocean_mixed_layer_thickness_defined_by_*
> ??? >> >> >>
> ??? >> >> >> Hi all,
> ??? >> >> >>
> ??? >> >> >> It seems that my question did not attract much response. :(
> ??? >> >> >>
> ??? >> >> >> Is it because no one knows how to use these standard
> names and
> ??? >> >> >> properly encode the "quantity that differs from its
> surface value by a certain amount"?
> ??? >> >> >>
> ??? >> >> >> Giving it more thoughts I feel that I need new standard
> names
> ??? >> >> >> to describe this properly.
> ??? >> >> >>
> ??? >> >> >> Would it make sense to describe it this way:
> ??? >> >> >>
> ??? >> >> >> float swtd ;
> ??? >> >> >> swtd:standard_name =
> ??? >> >> >> "sea_water_temperature_difference_wrt_sea_surface" ;
> swtd:units
> ??? >> >> >> = "degC" ; swtd:axis = "Z" ; swtd:positive = "down" ;
> ??? >> >> >> swtd:long_name = "temperature difference wrt its surface
> value"
> ??? >> >> >>
> ??? >> >> >> float omlt(t, j, i) ;
> ??? >> >> >> omlt:standard_name =
> ??? >> >> >> "ocean_mixed_layer_thickness_defined_by_temperature" ;
> ??? >> >> >> omlt:units = "m" ; omlt:coordinates = "time swtd1 latitude
> ??? >> >> >> longitude" ; omlt:long_name = "ocean mixed layer defined by
> ??? >> >> >> difference of temperature from surface"
> ??? >> >> >>
> ??? >> >> >> and the scalar value swtd can be 0.5 degC, 1.0 degC, etc.
> ??? >> >> >>
> ??? >> >> >> In this case, I need standard names working with
> temperature,
> ??? >> >> >> sigma_theta and
> ??? >> >> >> sigma_t:
> ??? >> >> >>
> ??? >> >> >> sea_water_temperature_difference_wrt_sea_surface
> ??? >> >> >> sigma_theta_difference_wrt_sea_surface
> ??? >> >> >> sigma_t_difference_wrt_sea_surface
> ??? >> >> >>
> ??? >> >> >>
> ??? >> >> >> any quick suggestions are very welcome!
> ??? >> >> >>
> ??? >> >> >> thanks
> ??? >> >> >> /S?bastien
> ??? >> >> >>
> ??? >> >> >> ----- Original Message -----
> ??? >> >> >> > From: "Sebastien Villaume" <sebastien.villaume at ecmwf.int>
> ??? >> >> >> > Sent: Wednesday, 4 April, 2018 14:04:42
> ??? >> >> >> > Subject: [CF-metadata] how to use
> ??? >> >> >> > ocean_mixed_layer_thickness_defined_by_*
> ??? >> >> >>
> ??? >> >> >> > Dear list,
> ??? >> >> >> >
> ??? >> >> >> > I have a question regarding the use of the standard
> names of
> ??? >> >> >> > the form
> ??? >> >> >> > ocean_mixed_layer_thickness_defined_by_*
> ??? >> >> >> >
> ??? >> >> >> > the definition from the official standard name table 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 temperature, sigma or sigma_theta is the
> level at
> ??? >> >> >> > which the quantity indicated differs from its surface
> value by a certain amount."
> ??? >> >> >> >
> ??? >> >> >> > From what I understand, in the case of
> ??? >> >> >> > ocean_mixed_layer_thickness_defined_by_temperature, I
> should
> ??? >> >> >> > specify some quantity as a scalar (Z axis), but it is
> ??? >> >> >> > actually a temperature difference that I need to
> encode, not
> ??? >> >> >> > a plain temperature : temp_surf - temp_base_level =
> ??? >> >> >> > temp_delta_defining_mixed_layer_thickness
> ??? >> >> >> >
> ??? >> >> >> > if it was simply a temperature I would maybe use:
> ??? >> >> >> >
> ??? >> >> >> > float swpt ;
> ??? >> >> >> > swpt:standard_name = "sea_water_potential_temperature" ;
> ??? >> >> >> > swpt:units = "degC" ; swpt:axis = "Z" ; swpt:positive =
> ??? >> >> >> > "down" ;
> ??? >> >> >> >
> ??? >> >> >> > but what I really want to encode is a temperature
> difference.
> ??? >> >> >> > How can I specify that? Is
> "sea_water_potential_temperature" the correct standard name to use?
> ??? >> >> >> >
> ??? >> >> >> >
> ??? >> >> >> > same question for
> ??? >> >> >> > ocean_mixed_layer_thickness_defined_by_sigma_theta, how
> do I encode a "difference" in sigma_theta?
> ??? >> >> >> >
> ??? >> >> >> > thanks,
> ??? >> >> >> >
> ??? >> >> >> > ____________________________________
> ??? >> >> >> >
> ??? >> >> >> > Dr. S?bastien Villaume
>
--
*******************************************************
* Nan Galbraith Information Systems Specialist *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 (508) 289-2444 *
*******************************************************
Received on Fri May 04 2018 - 10:38:49 BST
