Alison, > I am writing to ask if it is possible for a new unit of 'molecule' to be > added to the UDUNITS-2 XML database. The unit would be defined as follows: > > > <unit> > > <def>mol/6.02214179e23</def> Isn't the Avogadro constant 6.02214129e23? See <http://physics.nist.gov/cgi-bin/cuu/Value?na|search_for=physchem_in!>. > > <name> > > <singular>molecule</singular> > > <plural>molecules</plural> > > </name> > > <aliases> > > <name><singular>molec</singular></name> > > </aliases> > > </unit> > > This request is a result of a recent discussion on the CF-Metadata mailing > list in which we have agreed to create standard names for eight column > trace gas quantities with canonical units of mole m-2. However, the > common practice in the atmospheric chemistry community is to use units > of molecule cm-2. These latter units could be used in the netCDF file > and converted to the CF canonical unit if a definition for 'molecule' > were to be added to UDUNI TS. It's a possibility. You could, of course, add this definition to a "local definitions" file (say "$prefix/share/udunits/udunits2-local.xml"; where "$prefix" is the top-level installation directory) and then include that file in the file "$prefix/share/udunits/udunits2.xml". I presume, however, that you would want this definition to be an "official" unit (i.e., one supported by the UDUNITS-2 package and, consequently, distributed with the package). Correct? > (The CF discussion started in 2012 at > > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2012/056052.html > > and following posts in the same thread and recently concluded in > > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056207.html > > and following posts). Incidentally, I'm a little surprised to see that you included the word "mole" in the names of the physical quantities. The NIST frowns on this because it includes a unit in the name (see section 8.6.2 of <http://physics.nist.gov/Pubs/SP811/sec08.html>). I would have gone with names like areic_amount_of_substance_of_tropospheric_nitrogen_dioxide Oh well. Not my call. :-) I'll see about putting "molecules" in the next release -- providing we can agree on the Avogadro constant. > Kind regards, > Alison Pamment (CF Standard Names manager) > > ------ > Alison Pamment Tel: +44 1235 778065 > NCAS/British Atmospheric Data Centre Email: address@hidden > STFC Rutherford Appleton Laboratory > R25, 2.22 > Harwell Oxford, Didcot, OX11 0QX, U.K. Regards, Steve Emmerson Ticket Details =================== Ticket ID: XJX-726297 Department: Support UDUNITS Priority: Normal Status: Closed
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