[CF-metadata] standard names for chemistry

From: Schultz, Martin <m.schultz>
Date: Fri, 24 Oct 2008 08:26:29 +0200

Message: 3
Date: Thu, 23 Oct 2008 13:09:55 -0700 (PDT)
From: "Philip J. Cameronsmith1" <cameronsmith1 at llnl.gov>
Subject: Re: [CF-metadata] standard names for chemistry - MCM

> Hi Martin, et al.
>
> [...]
> This is why I was trying to point out that CF doesn't need to keep
separate lists for X, A, G, or
> any other set of species. We will only need a single list of species:
X.

agreed.

> We then have two choices: (i) force all quantities with species in X
to use the same units; or
> (ii) allow all possible units for all species in X, so that the user
can decide what makes most
> sense for any given specie, with the knowledge that the units can be
easily converted if needed
> (as long as the molar mass is known).
>
> It appears that you (Martin) and Jonathan prefer option (ii), and I
agree, even though it will
> mean a slightly larger list of standard names. :-)

no - I do prefer option (i), but it should be tied to the physical part
of the name, not the species or compound class. For mixing ratios
(either mass or molar), they are always unitless (we defined "1" as a
surrogate here), and the conversion is done by applying the molar mass
(which - to re-enforce - must be contained in the attributes).

In response to Jonathan and Alison: OK - the mixing ratio is different
if normalized to moist air instead of dry air. But in my humble opinion,
our concept should then suggest

       "mass_fraction_of_water_vapour_in_moist_air"

I believe there was a discussion on "mixing_ratio" versus
"mass_fraction" that may have almost been as long as the "expressed"
discussion. Thanks for reminding me about the latter - I was just trying
to think from the standpoint of a programmer who might wish to write a
tool for parsing standard names. Then it is always an extra hassle if
the "delimiters" are loosely defined (although I admit that
"_expressed_as" is as easy to search for as "_as_").

Best regards,

Martin


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Received on Fri Oct 24 2008 - 00:26:29 BST