Hi Glenn,
I would interpret 'm-3 kg' as (1/m3)*kg == kg/m3. Or did I misunderstand your email?
It does look funny to have the denominator unit first, though.
Best wishes,
Philip
-----------------------------------------------------------------------
Dr Philip Cameron-Smith, pjc at llnl.gov, Lawrence Livermore National Lab.
-----------------------------------------------------------------------
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-
> bounces at cgd.ucar.edu] On Behalf Of Comiskey, Glenn
> Sent: Wednesday, June 01, 2011 9:22 AM
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] udunits 1 or 2 for CF?
>
> Hi All,
>
> As a new comer to the world of metorological/oceanographic datasets, I
> am currently reading up on a number of subject matters including the
> use
> of the UDUNITS package and the use of version 1 or 2 for CF
> conformance.
> As a result of a URL kindly provided by Mike Grant, Plymouth Marine
> Laboratory I came across a posting by Andrew Clegg in March 2010:
>
> >I'm running into some problems regarding units in CF-compliant files.
> Up
> >until now I've been using udunits 1 to check units, but I recently
> tried
> >the CF checker which uses udunits2. There are some unit strings which
> >are valid in one but not the other. In particular, I am dealing with
> >milligrams per cubic meter. In udunits1, I used 'ukg m^-3', which
> >udunits2 rejects as invalid. udunits2 accepts 'mg m^-3' (which is much
> >better!), but udunits1 interprets this as to do with gravity. Because
> of
> >this, I can't include a unit string which is generally compatible with
> > udunits...
>
> My query relates to the specifications quoted for dealing with
> milligrams per cubic meter values, i.e. 'ukg m^-3' for version 1, and
> 'mg m^-3' for version 2. When I enter either value, or indeed 'mg/m3',
> into my installed version 1 (v1.12.11) of 'udunits' it reports the
> definition as '1e-06 kilogram metre-3' implying a unit value of
> '0.000001 kg/m3' - and what I would expect, i.e. kilograms per cubic
> metre.
>
> However, when I enter the same values into my installed version 2
> (v2.1.23) of 'udunits2' it reports the definition as '1e-06 m-3 kg'
> implying a unit value of '0.000001 m3/kg' - and not what I would
> expect,
> i.e. cubic metres per kilogram.
>
> Has anyone else noted this, or can somebody correct my interpretation
> of
> the meaning of 'm-3 kg'.
>
> Kind regards,
>
> Glenn Comiskey
> Data System Administrator
>
> Fugro Global Environment & Ocean Sciences
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Received on Wed Jun 01 2011 - 10:45:54 BST
