[CF-metadata] New name: fugacity of CO2

Lowry, Roy K. rkl at bodc.ac.uk
Fri Oct 5 07:44:22 MDT 2018


Dear All,


I'm happy with James's updated sentence. It says the same thing but is clearer. Once the fCO2 name has been added we could consider using it to upgrade other partial pressure definitions.


I think the last sentence is there to conform to a definition pattern that includes some less familiar substances. I'm equally happy with it or without it.


Cheers, Roy.


I have now retired but will continue to be active through an Emeritus Fellowship using this e-mail address.


________________________________
From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of James Orr <James.Orr at lsce.ipsl.fr>
Sent: 05 October 2018 14:26
To: Alison Pamment - UKRI STFC
Cc: 'Halloran, Paul'; cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] New name: fugacity of CO2

Hi Allison, Paul, Roy, et al.,

I would suggest to replace the 3rd sentence

"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."

with the following:

"The partial pressure of a gaseous constituent of air is the pressure that it
would exert if all other gaseous constituents were removed, assuming the volume,
the temperature, and its number of moles remain unchanged."

The description would then become as follows:

'The fugacity is the measured pressure (or partial pressure) of a real gas
corrected for the intermolecular forces of that gas, which allows that corrected
quantity to be treated like the pressure of an ideal gas in the ideal gas
equation PV = nRT. 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 that it would exert if
all other gaseous constituents were removed, assuming the volume, the
temperature, and its number of moles remain unchanged. The chemical formula for
carbon dioxide is CO2.'

In addition, is the last sentence useful given that it is common knowledge?

Thanks,

Jim

On Thu, 4 Oct 2018, Alison Pamment - UKRI STFC wrote:

> Dear Paul,
>
> Thank you for proposing this new standard name and thanks also to Roy, Jim and Jonathan for their comments.
>
> I think the proposal as it now stands is:
> fugacity_of_carbon_dioxide_in_sea_water (Canonical units: Pa)
> 'The fugacity is the measured pressure (or partial pressure) of a real gas corrected for the intermolecular forces of that gas, which allows that corrected quantity to be treated like the pressure of an ideal gas in the ideal gas equation PV = nRT. 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 chemical formula for carbon dioxide is CO2.'
>
> Paul, please can you confirm if this is all okay? If so, I think the name can be accepted and included in the next update to the table.
>
> Best wishes,
> Alison
>
> ------
> Alison Pamment                                 Tel: +44 1235 778065
> NCAS/Centre for Environmental Data Archival    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 <cf-metadata-bounces at cgd.ucar.edu> On Behalf Of Halloran, Paul
> Sent: 26 September 2018 12:59
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New name: fugacity of CO2
>
> Thanks very much Jim.
>
> Just to clarify (in light of Jim’s second point), my argument around air-sea CO2 flux which I put forward to support my suggestion that we include fugacity is that an imprecise conversion from fugacity of CO2 to pCO2 to allow one to submit data as a compliant netcdf (due to potentially not having the the other required variables available at the correct frequency), while likely to only result in small numerical errors could have bigger implications if then used to calculate air-sea CO2 flux.
>
> Thanks,
> Paul
>
>> Hi Paul, Roy, et al.,
>>
>> A couple of points regarding fugacity.
>>
>> 1) In the proposed definition of fugacity, the first sentence could be
>> misunderstood.  I suggest changing it to the following:
>>
>> The fugacity is the measured pressure (or partial pressure) of a real
>> gas corrected for the intermolecular forces of that gas, which allows
>> that corrected quantity to be treated like the pressure of an ideal
>> gas in the ideal gas equation PV = nRT.
>>
>> 2) The air-sea flux of a gas does not depend on its fugacity, only its
>> partial pressure (i.e., in both the atmosphere and ocean).
>>
>> Cheers,
>>
>> Jim
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