[CF-metadata] species as species in chemical and aerosol names - "mercury"

Christiane Textor christiane.textor at aero.jussieu.fr
Tue Oct 31 12:28:29 MST 2006

Dear all,

There was a comment on the mercury variables by Chris Holmes on the wiki 
page, which I copy here with my comments from

 > Dear Christiane and others,
 > I am confused by the expression "expressed_as_such". I have not been
 > part of the discussions that have created the current version of the
 > standard names, so I expect there is a good reason for using this
 > term, but I don't know it and the meaning is not intuitively clear to
 > me.
 > For example:
 > surface_dry_deposition_mass_flux_of_divalent_mercury_expressed_as_such
 > Does this mean that the corresponding variable gives the mass of the
 > divalent mercury compound that is dry deposited? Rather than the mass
 > of mercury within the deposited mercury compound?

I meant to refer to the the mass of mercury within the deposited mercury 
compound, but is this appropriate?

NICOLA, IAN: Thank you for commenting on this!

 > Some names are still confusing (e.g. the dry_aerosol entries):
 > If I am interpreting the term "expressed_as" correctly, maybe this
 > should be:
 > -Chris

The problem is that in CF composed species should be expressed 'as_such' 
if possible. Therefore, when I wrote 
mercury_expressed_as_such_dry_aerosol I was referring to the total 
aerosol mass, not only the mercury contained in it. Is this unclear? Or 
not appropriate (Nicole, Ian)?

Thank you very much for your comments! See also my previous email on 


Jonathan Gregory a écrit :
> Dear all
> Since Alison has reminded us this is still under discussion, I'd like to ask
> again whether anyone has a better idea than to use the phrases
> X_expressed_as_Y, or X_expressed_as_such, if X=Y for mass fluxes of chemical
> species, to indicate that there is a flux of X (carbon dioxide, for instance)
> but the mass units count it in terms of Y (carbon, for instance). Are these
> phrase clear enough?
> Cheers
> Jonathan
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Christiane Textor
GMES France Atmosphère - GEMS France
Service d'Aéronomie INSU CNRS, Tour 46, RDC # 2
Université Pierre et Marie Curie, Boite 102
4 place Jussieu
75252 Paris Cédex 05

Tel: ++33
Fax: ++33
Email: christiane.textor at aero.jussieu.fr

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