Dear Alejandro and Markus,
Just picking up on Alejandro's proposal. I like the suggestion of
single_scattering_albedo_in_air_due_to_ambient_aerosol_particles (canonical units:1 (dimensionless)).
This is indeed consistent with the syntax of existing names. The "due_to_ambient_aersol_particles" phrase should be understood to mean that the scattering is indeed due to the particulate component of the aerosol and not the surrounding air. We have standard definition text that should make all that clear:
' "Single scattering albedo" is the fraction of radiation in an incident light beam scattered by the particles of an aerosol reference volume for a given wavelength. It is the ratio of the scattering and the extinction coefficients of the aerosol particles in the reference volume. A coordinate variable with a standard name of radiation_wavelength or radiation_frequency should be included to specify either the wavelength or frequency. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which t
he quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity" and "air_temperature". The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase.'
Alejandro, if you are happy with this then I think the name can be accepted for inclusion in the standard name table.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
> -----Original Message-----
> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf
> Of Bodas-Salcedo, Alejandro
> Sent: 20 January 2016 09:37
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard name for aerosol single scattering
> albedo
>
> Dear Markus,
>
> Thanks for your comment. I'm happy with the change to a population of
> particles. As you say, it's a more practical definition. I find the first sentence
> a bit difficult, though. What about the following?
>
>
> Definition: Fraction of radiation in an incident light beam scattered by the
> particles of an aerosol reference volume as a function of wavelength. It is
> the ratio of the scattering and the extinction coefficients of the aerosol
> particles in the reference volume. A coordinate of radiation_wavelength or
> radiation_frequency should be included to specify either the wavelength or
> frequency.
>
> Regarding the humidity state, perhaps we should follow the definition for
> the extinction coefficient, and use the name
>
> single_scattering_albedo_in_air_due_to_ambient_aerosol_particles
>
> My only reservation is that this seems to refer to the optical properties of
> aerosols plus the molecular atmosphere, not only aerosols.
>
> Regards,
>
> Alejandro
>
>
> > -----Original Message-----
> > From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On
> Behalf Of
> > Markus Fiebig
> > Sent: 19 January 2016 12:49
> > To: cf-metadata at cgd.ucar.edu
> > Subject: Re: [CF-metadata] New standard name for aerosol single
> scattering albedo
> >
> > Dear Alejandro,
> >
> > after reading your mail, I was surprised to realise that
> > aerosol_single_scattering_albedo in fact hadn't been defined yet.
> >
> > However, the definition you propose seems to me rather unusual. You
> define the
> > single scattering albedo with respect to a single particle as ratio of
> > cross-sections, i.e. as truly microscale property. From the multitude of
> > particles contained in an aerosol, how do you determine which particle
> you refer to?
> >
> > From my experience, it's more usual to define the single scattering albedo
> as
> > ratio of scattering and extinction coefficient of a particle population, i.e.
> an
> > effective property for the ensemble of particles contained in the aerosol.
> How
> > about this:
> >
> > Definition: Fraction of radiation in an incident light beam interacting with
> the
> > particles of an aerosol reference volume and scattered by these particles
> as a
> > function of wavelength. It is the ratio of the scattering and the extinction
> > coefficients of the aerosol particles in the reference volume. A coordinate
> of
> > radiation_wavelength or radiation_frequency should be included to
> specify either
> > the wavelength or frequency.
> >
> > Having said that, should we also consider to include the humidity state of
> the
> > aerosol? That would require relative_humidity as additional coordinate
> variable.
> >
> > Best regards,
> > Markus
> >
> > Am 19.01.2016 um 10:47 schrieb Bodas-Salcedo, Alejandro:
> > > Dear All,
> > >
> > > I'd like to propose a new standard name, which as far as I can see doesn't
> > currently exist in the CF table:
> > >
> > > Name: aerosol_single_scattering_albedo
> > > Units: 1
> > > Description: Fraction of radiation scattered out of a pencil of radiation
> after one
> > encounter with an aerosol particle for a given wavelength. It is the ratio
> between the
> > scattering cross-section and the extinction cross-section. A coordinate of
> > radiation_wavelength or radiation_frequency should be included to
> specify either the
> > wavelength or frequency.
> > >
> > >
> > > Thanks,
> > >
> > > Alejandro
> > >
> >
> > --
> > Dr. Markus Fiebig
> > Senior Scientist
> > Dept. Atmospheric and Climate Research (ATMOS)
> > Norwegian Institute for Air Research (NILU)
> > P.O. Box 100
> > N-2027 Kjeller
> > Norway
> >
> > Tel.: +47 6389-8235
> > Fax : +47 6389-8050
> > e-mail: Markus.Fiebig at nilu.no
> > skype: markus.fiebig
> >
> > P Please consider the environment before printing this email and
> attachments
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Received on Wed Mar 02 2016 - 10:39:51 GMT
