Hi Again,
Like it or not the oceanograpghic domain is using:
mass of solute per volume of solvent
mass of solute per unit mass of solvent
moles of solute per unit volume of solvent
moles of solute per unit mass of solute
volume of solute per unit mass of solvent
volume of solute per unit volume of solvent
depending on community within the domain. Following my understanding of CF each of these needs to be addressed by the Standard Name system through a consistent syntax. What we need to do is establish a convention for this, which is what I see Jonathan's efforts addressing. Any advances on his conventions obviously need consideration.
Cheers, Roy.
________________________________________
From: Christiane Textor [christiane.textor at lsce.ipsl.fr]
Sent: 30 April 2009 20:41
To: Lowry, Roy K; Lowry, Roy K
Cc: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] new standard name request for pH
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 - 14:41:42 BST
