On Wed, 22 Oct 2008 13:00:47 -0700 (PDT) Philip J. Cameronsmith wrote:
Subject: Re: [CF-metadata] standard names for chemistry - MCM
"[...] In practice, gas phase chemicals are typically recorded using number of
moles, while aerosols are usually recorded using mass. Hence, the G for
gases, A for aerosols, and X for the combined set of G and A. But because
of the discussion above, it would be possible to force the gases and
aerosols to always have the same units for CF (as long as the Molar Mass
is recorded or prescribed for each specie)."
Hi Philip,
but this is why we define the physical quantity in the standard name, don't we?
Example: mass_fraction_of_ and mole_fraction_of_
In my view the "X", "A" and "G" is purely cosmetic to guide the choice of subset of matrix elements. Certain "names" (or properties) just don't make sense for gaseous compounds but are relevant for aerosols (and vice versa). [perhaps Christiane can jump in if I missed something here] There is no need to force anyone to adopt a specific unit. But your discussion about the "effective" molar mass reinforces the point that the molar mass that is assumed/used in the data must be documented so that people can easily convert from one into the other quantity. BTW: the distinction between mass and molar quantities also holds for all "tendency" terms - one can equally well "_due_to_deposition" as a mass quantity (useful for global budgets) or a molar quantity (useful for other things).
"[...] Another option is for CF to allow all possible units for each specie:
moles_of_X
mass_of_X
carbons_of_X
etc..."
As Jonathan said, this is exactly the reason for the "_expressed_as_" tag. BTW: Do we really need the "expressed" in this? "_as_" should also do the job, no? Some of the standard names have become rather long already...
Best regards,
Martin
< Dr. Martin G. Schultz, ICG-2, Forschungszentrum J?lich >
< D-52425 J?lich, Germany >
< ph: +49 (0)2461 61 2831, fax: +49 (0)2461 61 8131 >
< email: m.schultz at fz-juelich.de >
< web:
http://www.fz-juelich.de/icg/icg-2/m_schultz >
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Forschungszentrum J?lich GmbH
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Vorsitzende des Aufsichtsrats: MinDir'in B?rbel Brumme-Bothe
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Dr. Sebastian M. Schmidt
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Received on Thu Oct 23 2008 - 01:50:50 BST
