[CF-metadata] new standard names request

Allen Jordan - NOAA Affiliate allen.jordan at noaa.gov
Wed Mar 29 10:08:23 MDT 2017


Hello Alison.  Thank you for the detailed information.  I will review your
suggested names with my coworkers and get back to you.  It might take a
couple days as my supervisor is out of town until Friday.  We're trying to
get the names sorted out for our NOAA NCEI BEDI data submission, which uses
the NetCDF format with the CF conventions.

On Wed, Mar 29, 2017 at 6:49 AM, <alison.pamment at stfc.ac.uk> wrote:

> Hi Allen,
>
> Thanks for your standard name proposals and thanks to Steve and Roy for
> the discussion.
>
> We could introduce names for volume_mixing_ratio as Roy suggests and I am
> OK with this if it is your preferred approach. However, I note that where
> we have referred to 'mixing_ratio' in other names such as
> humidity_mixing_ratio and cloud_liquid_water_mixing_ratio these are
> actually defined as mass fractions. Indeed, for chemical species other than
> H2O we would probably have given them mass_fraction names.
>
> An alternative to describing your quantities as volume_mixing_ratios would
> be to call them volume_fractions. We have many existing mass_fraction and
> mole_fraction names for atmospheric quantities and five existing
> volume_fraction names for soil water quantities. Whichever names we choose,
> Roy is correct that the canonical unit would be simply '1', i.e. these are
> dimensionless quantities. You could still specify a unit of 1e-6 or 1e-9 in
> your data files as that would be completely compatible with the canonical
> units.
>
> For existing water vapor quantities we have distinguished between dry and
> moist air (humidity_mixing_ratio is the ratio of the mass of water vapor to
> the mass of dry air; specific_humidity is the mass fraction of water vapor
> in moist air.) You say that your names are for weather balloon data so I
> assume we are talking about moist air - we should include that in the
> definition.
>
> Drawing all this together, my suggestion for your standard names would be:
>
> volume_fraction_of_water_vapor_in_air (canonical units:1)
> ' "Volume fraction" is used in the construction volume_fraction_of_X_in_Y,
> where X is a material constituent of Y. The quantity with standard name
> volume_fraction_of_water_vapor_in_air is the volume fraction of water
> vapor in moist air.'
>
> volume_fraction_of_ozone_in_air (canonical units:1)
> ' "Volume fraction" is used in the construction volume_fraction_of_X_in_Y,
> where X is a material constituent of Y. The chemical formula for ozone is
> O3. The IUPAC name for ozone is trioxygen.'
>
> I appreciate that the information regarding ppmv and ppbv is important for
> your data but I suggest that rather than putting it in the standard name,
> units or definition, a better approach would be to also include a long_name
> attribute in your metadata. This is a non-standardized text string so you
> could specify something like the following:
>
> dimensions:
>   pressure = 100 ;
>
> variables:
>
>   float pressure(pressure) ;
>     pressure:standard_name = "air_pressure" ;
>     pressure:units = 'Pa' ;
>
>   float wv(pressure) ;
>     wv:standard_name = "volume_fraction_of_water_vapor_in_air " ;
>     wv:units = "1e-6" ;
>     wv:long_name = "atmospheric water vapor mixing ratio in parts per
> million by volume" ;
>
>   float ozone(pressure) ;
>     ozone:standard_name = "volume_fraction_of_water_vapor_in_air " ;
>     ozone:units = "1e-9" ;
>     ozone:long_name = "atmospheric water vapor mixing ratio in parts per
> billion by volume" ;
>
> If you could let me know whether you prefer the volume_mixing_ratio or
> volume_fraction standard names then I think we can agree these quantities
> and put them in the April update to the standard name table.
>
> Best wishes,
> Alison
>
> ------
> Alison Pamment                                                       Tel:
> +44 1235 778065
> Centre for Environmental Data Analysis         Email:
> alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Campus, Didcot, OX11 0QX, U.K.
>
>
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> Lowry, Roy K.
> Sent: 01 March 2017 08:54
> To: CF Metadata Mail List
> Subject: Re: [CF-metadata] new standard names request
>
> Forgot to set 'reply all'.....
>
> Hi Allen,
>
> As I tried to explain in my last message the way things work in CF is that
> the Standard Name is associated with a CANONICAL unit. This is an
> expression of the dimensions of the measurement and NOT the actual unit of
> measure, which is stored in the NetCDF. For anything in ppt, ppm, ppb etc.
> the Canonical unit used is 'dimensionless'.
>
> 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: Allen Jordan - NOAA Affiliate <allen.jordan at noaa.gov>
> Sent: 28 February 2017 22:40
> To: Lowry, Roy K.
> Cc: Steve Emmerson; CF Metadata Mail List
> Subject: Re: [CF-metadata] new standard names request
>
> Hi Roy and Steve.  Your modified names will work fine.  I would prefer
> units of "ppm" and "ppb" as they match our historical naming.  I'm very new
> to the CF Conventions, please bear with me.  Here is the modified request
> for new fields:
>
> name: volume_mixing_ratio_of_water_vapor_in_air
> description: The atmospheric water vapor mixing ratio in parts per million
> by volume.
> units: ppm
>
> name: volume_mixing_ratio_of_ozone_in_air
> description: The atmospheric ozone mixing ratio in parts per billion by
> volume.
> units: ppb
>
> I'll be sure to include the units as attributes of each variable.
>
> Thanks.
> - Allen
>
> On Tue, Feb 28, 2017 at 2:40 AM, Lowry, Roy K. <rkl at bodc.ac.uk> wrote:
>
> Hi Steve,
>
> I think there is a CF precedent would pacify you a little here, which is
> to have Standard Names of the form 'volume_mixing_ratio' with canonical
> units of dimensionless such as volume_mixing_ratio_of_oxygen_at_stp_in_sea_water.
> I would suggest following this practice in this case with:
>
> volume_mixing_ratio_of_water_vapor_in_air
> volume_mixing_ratio_of_ozone_in_air
>
> A note to Allen is that your actual units including scaling factor are
> explicity included in CF NetCDF as a parameter attribute.
>
> 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 Steve
> Emmerson <emmerson at ucar.edu>
> Sent: 27 February 2017 22:04
> To: Allen Jordan - NOAA Affiliate
> Cc: CF Metadata Mail List
> Subject: Re: [CF-metadata] new standard names request
>
> BEGIN RANT
>
> This is the kind of stuff that I don't like: putting additional (and
> unnecessary) semantics into the unit specification. "ppm" is bad enough
> (1e-6 would be better) but *volume*!
>
> The attributes of a physical quantity are attributes of the quantity
> itself -- *not* its unit. If a physical quantity is atmospheric mixing
> ratio by volume, then name it as such and leave the unit alone. The
> alternative is to pollute the unit namespace with "volume", "mass",
> "carbon", and whatever else people think up -- leading to a unending
> additions to the units database.
>
> Call the quantity "atmospheric water vapor mixing ratio by volume" and
> specify the unit as "1e-6" (or "ppm" if you must).
>
> Lest you think I'm alone in this, see sections 7.4 and 7.5 of <
> https://www.nist.gov/pml/nist-guide-si-chapter-7-rules-
> and-style-conventions-expressing-values-quantities>.
>
> NIST Guide to the SI, Chapter 7: Rules and Style ...
> www.nist.gov
> 7.1 Value and numerical value of a quantity The value of a quantity is its
> magnitude expressed as the product of a number and a unit, and the number
> multiplying the ...
>
>
> END RANT
>
> Thanks for letting me get this off my chest. :-)
>
>
> Regards,
> Steve Emmerson
>
> On Mon, Feb 27, 2017 at 2:21 PM, Allen Jordan - NOAA Affiliate <
> allen.jordan at noaa.gov> wrote:
> I would like to add two standard names for the NOAA GMD OZWV group's
> weather balloon data:
>
> name: water_vapor_mixing_ratio
> description: The atmospheric water vapor mixing ratio in parts per million
> by volume.
> units: ppmv
>
> name: ozone_mixing_ratio
> description: The atmospheric ozone mixing ratio in parts per billion by
> volume.
> units: ppbv
>
>
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