Hi All,
I haven't noticed any discussion in the email stream about the type of diameter.
There are several physically different diameters that get used in the aerosol community, the main ones being:
1) Actual, or geometric diameter (But what does that mean for non-spherical particles? Some are very non-spherical.)
2) Effective diameter (Volume divided by surface area [with a 1/3 geometric factor]. Avoids ambiguity for non-spherical particles.)
3) Aerodynamic diameter (defined by its settling velocity: the diameter of a spherical drop with density of 1g/cm3 that will settle at the same rate as the particle of interest).
Since 2 & 3 can differ by more than a factor of two, it can make quite a difference
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 alison.pamment at stfc.ac.uk
> Sent: Monday, November 29, 2010 4:35 AM
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Correct name for aerosol size
> distributionexpressedin numbers ?
>
> Dear Bruno, Jonathan and Roy,
>
> Thanks all for your comments. As far as the standard name is
> concerned,
> I think we are agreed on aerosol_particle_diameter to describe the
> particle sizes. This would have an SI unit of m.
>
> This name is accepted for inclusion in the standard name table.
>
> ------
> Alison Pamment Tel: +44 1235 778065
> NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
> Rutherford Appleton Laboratory Email:
> alison.pamment at stfc.ac.uk
> Chilton, Didcot, OX11 0QX, U.K.
>
>
> > -----Original Message-----
> > From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-
> > bounces at cgd.ucar.edu] On Behalf Of Jonathan Gregory
> > Sent: 27 November 2010 14:21
> > To: cf-metadata at cgd.ucar.edu
> > Subject: [CF-metadata] Correct name for aerosol size
> > distributionexpressedin numbers ?
> >
> > Dear Bruno
> >
> > Either the geophysical quantity or the bin index could be the
> > coordinate
> > variable, with the other one being an auxiliary coordinate variable.
> > That
> > is an arbitrary choice. If you don't need the bin index, you don't
> have
> > to
> > have such a variable at all. Both
> >
> > SPP200_bins = 30 ;
> > int SPP200_bins(SPP200_bins) ;
> > float SPP200_median_particle_diameter(SPP200_bins) ;
> > float mic_conctab_SPP200_sync_1(time, SPP200_bins) ;
> > mic_conctab_SPP200_sync_1:coordinates =
> > "SPP200_median_particle_diameter" ;
> >
> > and
> >
> > SPP200_median_particle_diameter = 30;
> > int SPP200_bins(SPP200_median_particle_diameter) ;
> > float
> > SPP200_median_particle_diameter(SPP200_median_particle_diameter);
> > float mic_conctab_SPP200_sync_1(time,
> > SPP200_median_particle_diameter) ;
> > mic_conctab_SPP200_sync_1:coordinates = "SPP200_bins";
> >
> > would be OK. time does not need to be named in the coordinates
> > attribute,
> > since it is a coordinate variable. (You can list it there if you
> like,
> > but
> > it is not usual.)
> >
> > > One last question I couldn't solve : should
> > > "bounds="SPP200_bin_bounds" be a attribute of the simple index
> > variable
> > > ("SPP200_bins") or of the the geophysices coordinate
> > > ("SPP200_median_particle_diameter") ?
> >
> > The latter. It specifies bounds for the diameter values for the bins.
> >
> > Best wishes
> >
> > Jonathan
> > _______________________________________________
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> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> --
> Scanned by iCritical.
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Received on Mon Nov 29 2010 - 14:58:55 GMT
