Hi Roy,
Concerning my question 4) I am sorry for not having more carefully read
previous postings.
You write about concentration per mass. However, I think this is not
correct as concentration is generally related to volume in CF as far as
I know, see my 5) below. There is mass_concentration and
mole_concentration, but both is per unit volume.
I have checked old postings and I have found that this has been
previously discussed:
From godin at mbari.org Wed Jan 3 17:09:34 2007
Date: Wed Jan 3 17:11:17 2007
Subject: [CF-metadata] Proposed standard names for biological model outputs
In text books mole/mass is referred to as molality, but this is not a
commonly used expression. Anyway, I think if we use concentration in
different ways than previously defined, this will lead to confusion.
Best regards,
Christiane
Lowry, Roy K a ?crit :
> Hi Christiane,
>
> Please check out the previous postings. There are in fact 3 pH
> scales covering pH based on a concentration per kg: one based on H+,
> a second on H+ and bisulphate and a third on H+, bisulphate and HF.
> We did consider having 4 Standard names but I was arguing for just 2
> based on H+ alone to try and match the level of specialism covered
> with other areas.
>
> The negative log transform between the appropriate concentration term
> and 'pH' has always been taken as read by all involved in the
> discussion, but maybe we should be more explicit when it comes to
> term definitions.
>
> Oceanographers are moving towards expressing chemical data in the
> dimension moles/kg rather than moles/litre. We need a standardised
> convention to distinguish these as they have different canonical
> units and therefore need different Standard Names. I think the
> approach Jonathan is taking is the most sensible way to do this
> without large scale deprecation of existing names. We must always
> remember to include definitions and to read them: they are the key to
> eliminating confusion.
>
> Cheers, Roy.
>
> ________________________________________ From:
> cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu]
> On Behalf Of Christiane Textor [christiane.textor at lsce.ipsl.fr] Sent:
> 30 April 2009 17:13 To: Lowry, Roy K; Jonathan Gregory Cc:
> cf-metadata at cgd.ucar.edu Subject: Re: [CF-metadata] new standard name
> request for pH
>
> Dear all,
>
> I am not an expert ocean acidification at all, but there are some
> general questions I have concerning these names for the pH of sea
> water:
>
> 1) large scale medium Why not use sea_water (or ocean_) as a prefix
> as we have agreed on?
>
> 2) definded_by For the atmospheric chemistry names we have used
> expressed_as, why not use this here as well?
>
> 3) definition of pH (-log(H+))
>
> As far as I know the pH is defined as the negative logarithm of the
> concentration of H+ (or whatever else), this is missing in the
> suggested names. I would suggest to use expressed_as instead of
> defined_by to circumvent this problem.
>
> 4) definition of pH (N.B.S or free)
>
> I have checked the different definitions of the pH in sea water and
> it seems to me that the NBS and the free pH do not all refer to the
> concentration of H+ alone but consider also other ions, please see
> http://en.wikipedia.org/wiki?title=Talk:Ocean_acidification#cite_note-zeebe-0
> (rather bad page, but still..)
>
> Am I confused?
>
> 5) concentration For the atmospheric chemistry names we have
> mass_concentration and mole_concentration which is mass or mole per
> volume. This means that concentration always means per unit volume,
> and not per unit mass. If you say now concentration per unit mass,
> this is confusing.
>
> Best regards, Christiane
>
>
>
>
> _______________________________________________ CF-metadata mailing
> list CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
--
======================================================================
Christiane Textor
Laboratoire des Sciences du Climat et de l'Environnement
Unite Mixte de Recherche CEA-CNRS-UVSQ
LSCE/IPSL laboratoire CEA/CNRS/UVSQ
Saclay, Orme des Merisiers,
Bat. 701, Piece 3b, Point Courrier 129
F-91191 Gif-sur-Yvette Cedex
FRANCE
mailto: christiane.textor at lsce.ipsl.fr
Tel ++33 1 69 08 34 07 Fax ++33 1 69 08 77 16
GEOmon scientific coordinator http://www.geomon.eu
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Received on Thu Apr 30 2009 - 13:41:17 BST
