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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Received on Wed Mar 29 2017 - 06:49:32 BST
