Martin,

On 04/04/2011 09:37 AM, Schultz, Martin wrote:
>    if this is the direction to take, then we will need several "expressed_as" 
> standard_names for atmospheric chemistry. Typical example: volatile organic 
> compounds are often "expressed as" mass mixing ratio based on either their 
> molecular mass or in "grams C" which counts only the mass of the C atoms 
> (because this is what counts in the sense that it ultimately produces CO2 at 
> the end of the reaction chain). Hence, one would need things like
> "mass_mixing_ratio_of_ethane_in_air_expressed_as_carbon_mass" and many 
> similar ones. You can do the same with nitogen for species like NO, NO2, 
> HNO3, N2O, etc.

Not necessarily. If you have an ambiguous physical quantity (i.e., one
that can be expressed in multiple -- but incompatible -- units), then
you should be able to use its "unit" attribute to refine its meaning.

Note that the "unit" attribute could still be "clean" (i.e., without
attached information).

>     Still, there may then be a need to define "readable units" which would be 
> obtained from the combination of standard_name and units. I do sympathize 
> with people who prefer to read "nmol mol-1" on a plot rather than "1" (or 
> "1.e-9" in this case).

Indeed. In my opinion, every display application should allow the user
to specify non-default output units.

Regards,
Steve Emmerson
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