Dear list,

any more comments? can we move forward and agree on these new standard names?

thanks
/Sébastien

----- Original Message -----
> From: "Jonathan Gregory" <jonathan.greg...@ncas.ac.uk>
> To: cf-metadata@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.villa...@ecmwf.int>
> -----
> 
>> Date: Tue, 10 Apr 2018 10:36:21 +0000 (GMT-00:00)
>> From: Sebastien Villaume <sebastien.villa...@ecmwf.int>
>> To: cf-metadata@cgd.ucar.edu
>> Cc: "Lowry, Roy K." <r...@bodc.ac.uk>, Jonathan Gregory
>>      <j.m.greg...@reading.ac.uk>
>> 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)
>> 
>> 
>> 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.
>> 
>> /Sébastien
>> 
>> ----- Original Message -----
>> > From: "Jonathan Gregory" <j.m.greg...@reading.ac.uk>
>> > To: "Sebastien Villaume" <sebastien.villa...@ecmwf.int>
>> > Cc: cf-metadata@cgd.ucar.edu, "Lowry, Roy K." <r...@bodc.ac.uk>
>> > Sent: Friday, 6 April, 2018 14:24:18
>> > Subject: Re: [CF-metadata] how to  use 
>> > 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.villa...@ecmwf.int>
>> >> To: cf-metadata@cgd.ucar.edu
>> >> Cc: Jonathan Gregory <j.m.greg...@reading.ac.uk>, "Lowry, Roy K."
>> >>  <r...@bodc.ac.uk>
>> >> Subject: Re: [CF-metadata] how to use
>> >>  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!
>> >> 
>> >> /Sébastien
>> >> 
>> >> ----- Original Message -----
>> >> > From: "Lowry, Roy K." <r...@bodc.ac.uk>
>> >> > To: cf-metadata@cgd.ucar.edu, "Jonathan Gregory" 
>> >> > <j.m.greg...@reading.ac.uk>
>> >> > Sent: Thursday, 5 April, 2018 18:34:48
>> >> > Subject: Re: [CF-metadata] how to       use     
>> >> > ocean_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 
>> >> > enquir...@bodc.ac.uk.
>> >> > Please also use this e-mail if your requirement is urgent.
>> >> > 
>> >> > 
>> >> > 
>> >> > From: CF-metadata <cf-metadata-boun...@cgd.ucar.edu> on behalf of 
>> >> > Jonathan
>> >> > Gregory <j.m.greg...@reading.ac.uk>
>> >> > Sent: 05 April 2018 18:28
>> >> > To: cf-metadata@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.villa...@ecmwf.int>
>> >> > -----
>> >> > 
>> >> >> Date: Thu, 5 Apr 2018 13:55:50 +0000
>> >> >> From: Sebastien Villaume <sebastien.villa...@ecmwf.int>
>> >> >> To: CF Metadata <cf-metadata@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
>> >> >> /Sébastien
>> >> >> 
>> >> >> ----- Original Message -----
>> >> >> > From: "Sebastien Villaume" <sebastien.villa...@ecmwf.int>
>> >> >> > To: "CF Metadata" <cf-metadata@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. Sébastien 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.villa...@ecmwf.int
>> >> >> > ____________________________________
>> >> >> > _______________________________________________
>> >> >> > CF-metadata mailing list
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>> >> >> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>> >> > 
>> >> > 
>> >> > CF-metadata Info Page - mailman.cgd.ucar.edu
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>> >> > This is an unmoderated list for discussions about interpretation, 
>> >> > clarification,
>> >> > and proposals for extensions or change to the CF conventions.
>> >> > 
>> >> > 
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>> >> > 
>> >> > ----- End forwarded message -----
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