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.
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________________________________
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
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