Dear Maarten A mole is also a udunit, so mol m-3 and m-3 are different units, and quantities with those canonical units also have to have different standard_names. The standard_name indicates whether the quantity refers to number concentration or molar concentration. I am not sure if I've understood you correctly.
Cheers Jonathan ----- Forwarded message from Maarten Sneep <[email protected]> ----- > Date: Tue, 6 Jan 2015 18:10:22 +0100 > From: Maarten Sneep <[email protected]> > To: [email protected] > Subject: Re: [CF-metadata] New UDUnits units for information: "byte" and > "octet" > User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 > Thunderbird/31.2.0 > > Sorry for the delayed reply, > > On 28-11-14 11:29, Jonathan Gregory wrote: > >Dear all > > > >I agree with Steve and Roy about this: > > > >>>Now UDUnits has "molecule" and "byte". They (Steve) > >>>are receptive to well-justified proposals, so do not feel daunted > >>>in transmitting to them the suggestion for "photon". > >> > >>Adding such units is the wrong way to go about solving the problem of > >>adding quantity-semantics to data values. It would be much better to have > >>the names of the variables be things like > >> > >> "number_of_tents" > >> "number_of_clouds" > >etc. > >> > >>and whose units were "1" than to try to incorporate such semantic > >>information into a unit > > > >That is exactly what the CF standard says. From Sect 3.1 on "Units": > > > >"Descriptive information about dimensionless quantities, such as sea-ice > >concentration, cloud fraction, probability, etc., should be given in the > >long_name or standard_name attributes rather than the units." > > I don't agree completely. A concentration or column amount in mol/m3 > or mol/m2 respectively can be converted to/from number > concentrations or column densities expressed in molecules/cm3 or > molecules/cm2. However, the explicit "molecules" is essential here, > otherwise UDUnits will not be of help at all. 1/m3 is not equivalent > to mol/m3. > > And yes, I agree that you should not try to do this for 'tents', > 'moles' (the furry kind, [1]) or even aerosol particles. Molecules > and photons are an exception in my view because there are large > datasets out there that use explicit molecules and photons for these > 'things'. > > Best, > > Maarten Sneep > > [1] https://what-if.xkcd.com/4/ > -- > 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 ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
