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.
Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquiries at bodc.ac.uk. Please also use this e-mail if your requirement is urgent.
________________________________
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
To: Alison Pamment - UKRI STFC; 'Sebastien Villaume'; cf-metadata at cgd.ucar.edu
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
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
-----Original Message-----
From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Sebastien Villaume
Sent: 13 April 2018 16:07
To: cf-metadata at cgd.ucar.edu
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>
> To: cf-metadata at cgd.ucar.edu
> 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>
>> To: cf-metadata at cgd.ucar.edu
>> Cc: "Lowry, Roy K." <rkl at bodc.ac.uk>, Jonathan Gregory
>> <j.m.gregory at reading.ac.uk>
>> Subject: Re: [CF-metadata] how touse
>> ocean_mixed_layer_thickness_defined_by_*
>> X-Mailer: Zimbra 8.6.0_GA_1200 (ZimbraWebClient - FF52
>> (Linux)/8.6.0_GA_1200)
>>
>>
>> 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>
>> > To: "Sebastien Villaume" <sebastien.villaume at ecmwf.int>
>> > Cc: cf-metadata at cgd.ucar.edu, "Lowry, Roy K." <rkl at bodc.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>
>> >> To: cf-metadata at cgd.ucar.edu
>> >> Cc: Jonathan Gregory <j.m.gregory at reading.ac.uk>, "Lowry, Roy K."
>> >> <rkl at bodc.ac.uk>
>> >> Subject: Re: [CF-metadata] how touse
>> >> ocean_mixed_layer_thickness_defined_by_*
>> >> X-Mailer: Zimbra 8.6.0_GA_1200 (ZimbraWebClient - FF59
>> >> (Linux)/8.6.0_GA_1200)
>> >>
>> >> 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>
>> >> > To: cf-metadata at cgd.ucar.edu, "Jonathan Gregory"
>> >> > <j.m.gregory at reading.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.
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> >
>> >> > Please note that I partially retired on 01/11/2015. I am now
>> >> > only working 7.5 hours a week and can only guarantee e-mail
>> >> > response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquiries at bodc.ac.uk.
>> >> > Please also use this e-mail if your requirement is urgent.
>> >> >
>> >> >
>> >> >
>> >> > 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
>> >> > To: cf-metadata at cgd.ucar.edu
>> >> > 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>
>> >> >> To: CF Metadata <cf-metadata at cgd.ucar.edu>
>> >> >> Subject: Re: [CF-metadata] how to use
>> >> >> ocean_mixed_layer_thickness_defined_by_*
>> >> >> X-Mailer: Zimbra 8.6.0_GA_1200 (ZimbraWebClient - FF52
>> >> >> (Linux)/8.6.0_GA_1200)
>> >> >>
>> >> >> 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>
>> >> >> > To: "CF Metadata" <cf-metadata at cgd.ucar.edu>
>> >> >> > 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
>> >> >> >
>> >> >> > M.A.R.S. Analyst
>> >> >> > ECMWF Data Governance facilitator
>> >> >> >
>> >> >> > ECMWF
>> >> >> > Shinfield Park,
>> >> >> > Reading RG2 9AX, UK
>> >> >> > +44 (0)118 949 9301
>> >> >> > +44 (0)7825 521592
>> >> >> > sebastien.villaume at ecmwf.int
>> >> >> > ____________________________________
>> >> >> > _______________________________________________
>> >> >> > CF-metadata mailing list
>> >> >> > CF-metadata at cgd.ucar.edu
>> >> >> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>> >> >
>> >> >
>> >> > CF-metadata Info Page - mailman.cgd.ucar.edu
>> >> > mailman.cgd.ucar.edu This is an unmoderated list for discussions
>> >> > about interpretation, clarification, and proposals for
>> >> > extensions or change to the CF conventions.
>> >> >
>> >> >
>> >> >> _______________________________________________
>> >> >> CF-metadata mailing list
>> >> >> CF-metadata at cgd.ucar.edu
>> >> >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>> >> >
>> >> > ----- End forwarded message -----
>> >> > _______________________________________________
>> >> > CF-metadata mailing list
>> >> > CF-metadata at cgd.ucar.edu
>> >> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>> >> >
>> >> > This message (and any attachments) is for the recipient only.
>> >> > NERC is subject to the Freedom of Information Act 2000 and the
>> >> > contents of this email and any reply you make may be disclosed
>> >> > by NERC unless it is exempt from release under the Act. Any
>> >> > material supplied to NERC may be stored in an electronic records management system .
>> >> >
>> >> > _______________________________________________
>> >> > CF-metadata mailing list
>> >> > CF-metadata at cgd.ucar.edu
>> > > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> ----- End forwarded message -----
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
_______________________________________________
CF-metadata mailing list
CF-metadata at cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
_______________________________________________
CF-metadata mailing list
CF-metadata at cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
________________________________
This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system.
________________________________
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20180426/a6d5728e/attachment.html>
Received on Thu Apr 26 2018 - 08:59:54 BST
