Hi Alison,
The 'in equilibrium' in pCO2 definition refers to the air in the analytical equipment and so has nothing to do with air-sea interface equilibrium. pCO2 is measured by using something like a shower-head or a column full of marbles to equilibrate the water sample with a stream of air that is then passed into a gas analyser. Consequently, the Standard Name makes no statement about the depth from which the water was taken. The same would apply to methane.
Whilst it is usual to measure pCO2 in surface waters, I have come across measurements on water bottle samples collected at depth.
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.
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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: 29 March 2017 12:34
To: beate.geyer at hzg.de; cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] WG: proposal for two new standard_names and an additional chemical species
Dear Beate,
Thank you for your proposals.
As you have pointed out, we have an existing name 'surface_partial_pressure_of_carbon_dioxide_in_sea_water'. I completely agree that we should remove the sentence
' "Water" means water in all phases, including frozen i.e. ice and snow' from the definition as it really isn't necessary for this name. I will make that change in the April update to the standard name table.
The definition of the existing name includes the sentence 'The partial pressure of a dissolved gas in sea water is the partial pressure in air with which it would be in equilibrium' so clearly this is talking about equilibrium of partial pressures across the air-sea interface, i.e. at the surface. For the proposed name partial_pressure_of_carbon_dioxide_in_sea_water do you mean partial pressures at some arbitrary depth below the sea surface, even if these are not actually in physical contact with the surface itself? If so, then I agree we do need a new name.
For the methane name I would ask the same question. Certainly we can introduce a methane partial pressure name, but I'd like to understand whether it's at the surface or at some arbitrary depth.
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 beate.geyer at hzg.de
Sent: 20 February 2017 08:30
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] WG: proposal for two new standard_names and an additional chemical species
Dear all and especially the cf-metadata crew,
My colleagues and I apply for an expansion of the table of chemical species (
http://cfconventions.org/Data/cf-standard-names/docs/guidelines.html#id2799094): methane.
We apply to include partial_pressure_of_methane_in_sea_water (units: Pa)
with following description:
The partial pressure of a dissolved gas in sea water is the partial pressure in air with which it would be in equilibrium. The partial pressure of a gaseous constituent of air is the pressure which it alone would exert with unchanged temperature and number of moles per unit volume.
The description of 'surface_partial_pressure_of_carbon_dioxide_in_sea_water' includes the sentence
"Water" means water in all phases, including frozen i.e. ice and snow.
which does not fit in this context ? perhaps is an update possible here.
We apply to include the additional standard_name partial_pressure_of_carbon_dioxide_in_sea_water (units: Pa)
with the description
The partial pressure of a dissolved gas in sea water is the partial pressure in air with which it would be in equilibrium. The partial pressure of a gaseous constituent of air is the pressure which it alone would exert with unchanged temperature and number of moles per unit volume.
The reason for this applications is the conversion of our measurement data to cf-conform netCDF.
Thanks in advance for your help,
Beate Geyer
Institut f?r K?stenforschung
Dr. Beate Geyer
Regionale Atmosph?ren Modellierung
Telefon : +49 4152 87-1871
Telefax : +49 4152 87-41871
________________________________________
Helmholtz-Zentrum Geesthacht
Zentrum f?r Material- und K?stenforschung GmbH
Max-Planck-Stra?e 1 I 21502 Geesthacht I Deutschland/Germany
Gesch?ftsf?hrer/Board of Management: Prof. Dr. Wolfgang Kaysser, Dipl.-Ing. Michael Gan?
Vorsitzender des Aufsichtsrates/Chairman of the Supervisory Board: Ministerialdirigent Dr. Herbert Zeisel
Amtsgericht L?beck HRB 285 GE (Register Court)
Internet:
http://www.hzg.de
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