On 07-01-15 17:10, Steve Emmerson wrote:
Jonathan,
I think you meant to say that if a physical quantity has a different
dimensionality (not unit), then we have to give it a different name.
In my opinion, what's needed in this case is a package that understands
co-ordinate transformations -- in order to convert, for example, values
in units of "1e15/cm2" to values in units of "mol/m2". This is a rather
simple example and Maarten makes a good (though not yet convincing to
me) argument for simply modifying the UDUNITS database. One can imagine,
however, more complicated cases in which simple unit conversions are not
possible (e.g., converting between altitude and pressure). Such a
package would be easily capable of handling Maarten's conversion.
The only argument I'm making is that 'molecules' is available as a unit
equivalent to 'avogadros_number-1' (which is the case with the current
release of UDUnits). People who use 1/cm2 when they (implicitly) mean
molecules/cm2 get what they deserve IMHO.
As soon as you have molecules/cm2, then UDUnits can handle the
conversion as is. For other densities, say an aerosol particle count,
the conversion to mol is never needed, and number densities are fine
(and a look at the standard_names will confirm this).
So right now I'm not asking anything, as the most important scaled alias
for 'mol' is available. This will ease the transition to mol/m2 quite
significantly. It would be good to help the transition from photons to
mol (photons) as well, which was a request that started this whole
discussion in the first place.
Does this make the argument clearer?
Best,
Maarten Sneep
--
KNMI
T: 030 2206747
E: [email protected]
R: A2.14
_______________________________________________
CF-metadata mailing list
[email protected]
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
