Hi All,
After considerable thought, I do support addition of this std_name, but recommend that we add a comment to the description (as described below).
The problem is that
atmosphere_mole_content_of_ozone (proposed, units = moles/m2, typically expressed in DU)
and
equivalent_thickness_at_stp_of_atmosphere_ozone_content (already in CF, units = m, typically expressed in DU)
are essentially the same. Although they have nominally different units, the usual unit used in both cases is Dobson Units (DU). 1 DU was originally defined as 10 micrometers of ozone at STP (ie a unit of distance), but can equivalently defined as 446.2... micromoles/m2 (ie, related to 'moles/m2'), see
http://en.wikipedia.org/wiki/Dobson_unit. The conversion is trivially done through the ideal gas law.
A user putting ozone column data into CF is just as likely to use one std_name as the other, and use DU for the units in either case. It would be appropriate to compare the data directly (with no unit conversion if both are put in as DU).
Hence, different datasets may contain the same data using different std_names, which isn't ideal.
On the other hand, the official units are different, and we have a related issue where we have separate std_names for quantities in 'moles' and 'mass', which are often trivial to convert between in many cases.
If these were the only aspects to consider then I would be against the new std_name. However, there are many more species than ozone, and ozone is the only one that I see expressed as equivalent thickness. This means that we will surely end up wanting atmosphere_mole_content for other species, so it makes sense to have it for ozone too. For me, this tips the balance in favor of accepting the proposed std_name.
Unfortunately, I don't think we can mitigate the problems using an alias because the std_names have different official units.
Hence, I propose that we simply add a note at the end of the descriptions for atmosphere_mole_content_of_ozone and equivalent_thickness_at_stp_of_atmosphere_ozone_content alerting users to the existence of the other std_name:
"Note: Ozone columns can be stored in either equivalent_thickness_at_stp_of_atmosphere_ozone_content or atmosphere_mole_content_of_ozone."
Best wishes,
Philip
-----------------------------------------------------------------------
Dr Philip Cameron-Smith, pjc at llnl.gov, Lawrence Livermore National Lab.
-----------------------------------------------------------------------
> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> alison.pamment at stfc.ac.uk
> Sent: Thursday, December 06, 2012 5:33 AM
> To: Christophe.Lerot at aeronomie.be
> Cc: victoria.bennett at stfc.ac.uk; cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] new standard name proposal for total ozone in DU
>
> Dear Christophe and Roy,
>
> Thank you for the discussion; I think we are agreed! The name will go into the
> standard name table as follows:
>
> atmosphere_mole_content_of_ozone; mol m-2
> Definition: ' "Content" indicates a quantity per unit area. The "atmosphere
> content" of a quantity refers to the vertical integral from the surface to the top
> of the atmosphere. For the content between specified levels in the atmosphere,
> standard names including content_of_atmosphere_layer are used. The
> construction "atmosphere_mole_content_of_X" means the vertically integrated
> number of moles of X above a unit area. The chemical formula for ozone is O3.
> atmosphere_mole_content_of_ozone is usually measured in Dobson Units (DU)
> which are equivalent to 446.2 micromoles m-2.'
>
> This name is accepted for inclusion in the standard name table and will be added
> at the next update.
>
> Best wishes,
> Alison
>
> ------
> Alison Pamment Tel: +44 1235 778065
> NCAS/British Atmospheric Data Centre Email: alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Oxford, Didcot, OX11 0QX, U.K.
>
>
>
> > -----Original Message-----
> > From: Christophe Lerot [mailto:Christophe.Lerot at aeronomie.be]
> > Sent: 06 December 2012 12:48
> > To: Pamment, Alison (STFC,RAL,RALSP)
> > Cc: cf-metadata at cgd.ucar.edu
> > Subject: Re: [CF-metadata] new standard name proposal for total ozone
> > in DU
> >
> > Hi Alison and Roy,
> >
> > I think that the solution you proposed is suitable to the O3 community.
> >
> > Having the canonical unit (mol/m-2) for the O3 columns in the
> > vocabulary server is fine as long as it is not a problem to use a
> > different unit (Dobson Unit) in the NetCDF files. The important point
> > is that the variables are expressed in the commonly used units so that
> > the users can understand the file content at a glance.
> >
> > Best regards,
> > Christophe
> >
> > On 5/12/2012 11:30, alison.pamment at stfc.ac.uk wrote:
> > > Dear Roy and Christophe,
> > >
> > > As Roy says, we usually use SI units for the canonical unit in the
> > > standard
> > name table. There are a few exceptions, for example, age_of_sea_ice
> > has units of year and age_of_surface_snow has units of day, whereas
> > the SI unit for both quantities would be the second. Also, we allowed
> > some of the recently added salinity names to have canonical units of g
> > kg-1 which I'm not sure adheres strictly to SI. I think the reason for
> > having the exceptions was simply that they are the units that are
> > always used with the named quantities.
> > >
> > > For Christophe's ozone name, atmosphere_mole_content_of_ozone, the
> > proposed definition is ' "Content" indicates a quantity per unit area.
> > The "atmosphere content" of a quantity refers to the vertical integral
> > from the surface to the top of the atmosphere. For the content between
> > specified levels in the atmosphere, standard names including
> > content_of_atmosphere_layer are used. The construction
> > "atmosphere_mole_content_of_X" means the vertically integrated number
> > of moles of X above a unit area. The chemical formula for ozone is O3.'
> > Whatever we decide about the units, I think we should add the sentence
> > 'atmosphere_mole_content_of_ozone is usually measured in Dobson Units
> > which are equivalent to 446.2 micromoles m-2'.
> > >
> > > Roy's proposed solution of having canonical units of mol m-2 while
> > > using
> > Dobson Units in the data files is certainly consistent with the CF
> > conventions. As long as UDUNITS knows how to convert the units in the
> > file to the canonical units there is no problem. Christophe, would
> > that be acceptable to the ozone community?
> > >
> > > Roy, is there any technical reason why we couldn't map to Dobson
> > > Units in
> > the vocabulary server if that were the preferred solution?
> > >
> > > Best wishes,
> > > Alison
> > >
> > > ------
> > > Alison Pamment Tel: +44 1235 778065
> > > NCAS/British Atmospheric Data Centre Email:
> > alison.pamment at stfc.ac.uk
> > > STFC Rutherford Appleton Laboratory
> > > R25, 2.22
> > > Harwell Oxford, Didcot, OX11 0QX, U.K.
> > >
> > >
> > >
> > >> -----Original Message-----
> > >> From: Lowry, Roy K. [mailto:rkl at bodc.ac.uk]
> > >> Sent: 04 December 2012 10:23
> > >> To: Christophe Lerot
> > >> Cc: Pamment, Alison (STFC,RAL,RALSP); cf-metadata at cgd.ucar.edu
> > >> Subject: RE: [CF-metadata] new standard name proposal for total
> > >> ozone
> > in
> > >> DU
> > >>
> > >> Hello Cristophe,
> > >>
> > >> To be absolutely clear, I'm saying the data should be stored in the
> > >> NetCDF
> > in
> > >> Dobson Units, that the units parameter attribute in the NetCDF file
> > should
> > >> be Dobson Units, but that the canonical unit in the Standard Names
> > >> List
> > and
> > >> therefore the units mapped in our server should be moles per square
> > >> metre.
> > >>
> > >> Cheers, Roy.
> > >>
> > >> ________________________________________
> > >> From: Christophe Lerot [Christophe.Lerot at aeronomie.be]
> > >> Sent: 04 December 2012 10:20
> > >> To: Lowry, Roy K.
> > >> Cc: alison.pamment at stfc.ac.uk; cf-metadata at cgd.ucar.edu
> > >> Subject: Re: [CF-metadata] new standard name proposal for total
> > >> ozone
> > in
> > >> DU
> > >>
> > >> Dear Roy,
> > >>
> > >> Do you mean that the total ozone values should be given in moles
> > >> per square metre in the NetCDF files themselves? Or do you mean
> > >> that I should simply add a specific comment in the unit parameter
> > >> attribute to make clear that the values are provided in Dobson Unit?
> > >> The Dobson Unit is quite common for total ozone users and I'd
> > >> prefer to stay with this unit if possible.
> > >>
> > >> Cheers,
> > >> Christophe
> > >>
> > >> On 3/12/2012 15:39, Lowry, Roy K. wrote:
> > >>> Hello Alison,
> > >>>
> > >>> Surely the canonical unit for Dobson Units would be moles per
> > >>> square
> > >> metre, with Dobson Units appearing as the scaled unit in the units
> > >> parameter attribute. Making Dobson Units the canonical unit would
> > >> be
> > like
> > >> having cm/s rather than m/s as a canonical unit.
> > >>> Cheers, Roy.
> > >>> ________________________________________
> > >>> From: CF-metadata [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> > >> alison.pamment at stfc.ac.uk [alison.pamment at stfc.ac.uk]
> > >>> Sent: 03 December 2012 14:18
> > >>> To: cf-metadata at cgd.ucar.edu
> > >>> Subject: Re: [CF-metadata] new standard name proposal for total
> > >>> ozone
> > in
> > >> DU
> > >>> Dear Christophe and Jonathan,
> > >>>
> > >>> I also support this proposal. We don't currently have any standard
> > names
> > >> that use Dobson Units - I think UDUnits1 didn't support it.
> > >> However, since
> > it
> > >> is defined in UDunits2 I don't see any problem with adding it.
> > >>> Best wishes,
> > >>> Alison
> > >>>
> > >>> ------
> > >>> Alison Pamment Tel: +44 1235 778065
> > >>> NCAS/British Atmospheric Data Centre 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 Jonathan Gregory
> > >>>> Sent: 27 November 2012 20:52
> > >>>> To: cf-metadata at cgd.ucar.edu
> > >>>> Subject: [CF-metadata] new standard name proposal for total ozone
> > >>>> in
> > >> DU
> > >>>> Dear Christophe
> > >>>>
> > >>>>> So I'd like to propose the following variable name for total
> > >>>>> ozone columns based on recommendations I was given:
> > >>>>> - "atmosphere_mole_content_of_ozone" expressed in Dobson Units.
> > >>>>> Dobson Unit (DU) is already defined in the UDUNIT package ans is
> > >>>>> equivalent to 446.2 micromoles m-2.
> > >>>> This seems fine to me. It is consistent in construction with
> > >>>> existing names for a quantity in mol m-2.
> > >>>>
> > >>>> Best wishes
> > >>>>
> > >>>> Jonathan
> > >>>> _______________________________________________
> > >>>> CF-metadata mailing list
> > >>>> CF-metadata at cgd.ucar.edu
> > >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> > >>> --
> > >>> Scanned by iCritical.
> > >>> _______________________________________________
> > >>> 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
> > >> --
> > >> -----------------------------------------------------
> > >> Dr. Christophe LEROT
> > >> Belgian Institute for Space Aeronomy Chemistry & Physics of
> > >> Atmospheres Avenue circulaire, 3
> > >> 1180 Brussels
> > >> Belgium
> > >> phone: +32/(0)2-3730-407
> > >> mobile: +32/(0)472-81.87.00
> > >> mail: christophe.lerot at aeronomie.be
> > >> url: http://uv-vis.aeronomie.be/
> > >> -----------------------------------------------------
> > >>
> > >> 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.
> >
> > --
> > -----------------------------------------------------
> > Dr. Christophe LEROT
> > Belgian Institute for Space Aeronomy
> > Chemistry & Physics of Atmospheres
> > Avenue circulaire, 3
> > 1180 Brussels
> > Belgium
> > phone: +32/(0)2-3730-407
> > mobile: +32/(0)472-81.87.00
> > mail: christophe.lerot at aeronomie.be
> > url: http://uv-vis.aeronomie.be/
> > -----------------------------------------------------
> >
> >
>
> --
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Received on Thu Dec 06 2012 - 16:41:16 GMT
