Dear Martin,
Indeed, the quoted spectral region of 300 - 700 nm does come from the definition text of surface_downwelling_photosynthetic_radiative_flux_absorbed_by_vegetation. I am uncertain of the origin of this particular piece of text. I have done a brief online search on "photosynthetic radiation" and, as you say, the generally accepted definition does appear to be 400 - 700 nm. As this seems to be the more correct definition I will change the text for both standard names. This still allows for an individual data variable to have a coordinate variable with bounds giving a more precisely specified range of wavelengths if necessary.
We can also include definition text to say that the quantity is often referred to as "fraction of absorbed photosynthetically active radiation".
With a little more expansion of the definition to add in text that is normally included for standard names I think this now brings us to:
fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbed_by_vegetation (canonical units: 1)
'Downwelling radiation is radiation from above. It does not mean "net downward". The quantity with standard name fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbed_by_vegetation, often called fraction of absorbed photosynthetically active radiation (FAPAR), is the fraction of incoming solar radiation in the photosynthetically active radiation spectral region that is absorbed by a vegetation canopy. "Photosynthetic" radiation is the part of the spectrum which is used in photosynthesis e.g. 400-700 nm. The range of wavelengths could be specified precisely by the bounds of a coordinate of "radiation_wavelength". The surface called "surface" means the lower boundary of the atmosphere. "Vegetation" means any plants e.g. trees, shrubs, grass. In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.'
Is this OK?
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
> -----Original Message-----
> From: Claverie, Martin (GSFC-6190)[Science Collaborator]
> [mailto:martin.claverie at nasa.gov]
> Sent: 08 May 2015 19:43
> To: Pamment, Alison (STFC,RAL,RALSP); j.m.gregory at reading.ac.uk; cf-
> metadata at cgd.ucar.edu
> Subject: RE: [CF-metadata] New standard name request for FAPAR
>
> Dear Alison and Jonathan
>
> Ok, we can go forward and use
> "fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbe
> d_by_vegetation".
>
> however, I have 2 remarks:
> - the spectral range is more known as 400-700nm (cf for instance
> http://www.fao.org/gtos/doc/ECVs/T10/T10.pdf page 7) rather than 300-
> 700. Does 300-700 range come from the
> "surface_downwelling_photosynthetic_radiative_flux_absorbed_by_vegeta
> tion" definition ?
> - can we mention the term "fraction of absorbed photosynthetically active
> radiation" as an alternative name in the definition ?
>
> best
>
> Martin
> ________________________________________
> From: alison.pamment at stfc.ac.uk [alison.pamment at stfc.ac.uk]
> Sent: Friday, May 08, 2015 11:28 AM
> To: j.m.gregory at reading.ac.uk; cf-metadata at cgd.ucar.edu
> Cc: Claverie, Martin (GSFC-6190)[Science Collaborator]
> Subject: RE: [CF-metadata] New standard name request for FAPAR
>
> Dear Martin,
>
> Thank you for your proposal which has now been added to the list of
> standard names under discussion:
> http://cfeditor.ceda.ac.uk/proposals/1?status=active&namefilter=&propos
> erfilter=Claverie&descfilter=&unitfilter=&yearfilter=&filter+and+display=Fil
> ter.
>
> fraction_of_absorbed_photosynthetically_active_radiation (canonical units
> 1)
>
> I agree with Jonathan that
> fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbed
> _by_vegetation would be consistent with existing names.
>
> Based on the definition you have provided and those of other
> "photosynthetic" names, the full definition of this name would currently
> read:
> 'The fraction of incoming solar radiation in the photosynthetically active
> radiation spectral region that is absorbed by a vegetation canopy.
> "Photosynthetic" radiation is the part of the spectrum which is used in
> photosynthesis e.g. 300-700 nm. The range of wavelengths could be
> specified precisely by the bounds of a coordinate of
> "radiation_wavelength".'
>
> The definition text does allow for some variation of the precise
> wavelengths involved, so I think you would probably be OK to use the
> suggested name and accompany your data variable with a
> radiation_wavelength coordinate variable and bounds appropriate to your
> particular case.
>
> Best wishes,
> Alison
>
> > -----Original Message-----
> > From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On
> Behalf
> > Of Jonathan Gregory
> > Sent: 07 May 2015 16:18
> > To: cf-metadata at cgd.ucar.edu
> > Subject: Re: [CF-metadata] New standard name request for FAPAR
> >
> > Dear Martin
> >
> > OK. If that is the correct assumption, maybe your new quantity could be
> > called
> >
> >
> fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbed
> > _by_vegetation
> >
> > Best wishes
> >
> > Jonathan
> >
> >
> > ----- Forwarded message from "Claverie, Martin (GSFC-6190)[Science
> > Collaborator]" <martin.claverie at nasa.gov> -----
> >
> > > Date: Wed, 6 May 2015 17:50:01 +0000
> > > From: "Claverie, Martin (GSFC-6190)[Science Collaborator]"
> > > <martin.claverie at nasa.gov>
> > > To: Jonathan Gregory <j.m.gregory at reading.ac.uk>, "cf-
> > metadata at cgd.ucar.edu
> > > Subject: RE: [CF-metadata] New standard name request for FAPAR
> > >
> > > Dear Jonathan
> > >
> > > I think your assumption is correct : "the fraction of the
> > [surface_downwelling_photosynthetic_radiative_flux_in_air] which is
> > absorbed by the vegetation".
> > >
> > > However I need to check that
> > surface_downwelling_photosynthetic_radiative_flux_in_air is equivalent
> to
> > what we called in my community the "Photosynthetically active
> radiation".
> > >
> > > If so, we could mention
> > surface_downwelling_photosynthetic_radiative_flux_in_air variable in
> the
> > FAPAR definition.
> > >
> > > **********
> > > definition:
> > > The fraction of incoming solar radiation in the photosynthetically active
> > radiation spectral region (equivalent to
> > surface_downwelling_photosynthetic_radiative_flux_in_air) that is
> > absorbed by a vegetation canopy.
> > > **********
> > >
> > > best regards
> > >
> > > Martin
> > > ________________________________________
> > > From: Jonathan Gregory [j.m.gregory at reading.ac.uk]
> > > Sent: Wednesday, May 06, 2015 1:30 PM
> > > To: cf-metadata at cgd.ucar.edu
> > > Cc: Claverie, Martin (GSFC-6190)[Science Collaborator]
> > > Subject: Re: [CF-metadata] New standard name request for FAPAR
> > >
> > > Dear Martin
> > >
> > > > I am proposing the following standard name for Fraction of Absorbed
> > > > Photosynthetically Active Radiation (FAPAR), which is a GCOS Essential
> > > > Climate Variable (ECV).
> > > >
> > > > standard name:
> > > > fraction_of_absorbed_photosynthetically_active_radiation
> > > >
> > > > definition:
> > > > The fraction of incoming solar radiation in the photosynthetically active
> > > > radiation spectral region that is absorbed by a vegetation canopy.
> > > >
> > > > canonical units:
> > > > 1
> > >
> > > We have an existing standard name of
> > > surface_downwelling_photosynthetic_radiative_flux_in_air
> > > and I assume your proposal means the fraction of this which is absorbed
> > by
> > > the vegetation. Is that right? If so, it would be better to add to this
> > > existing name (without in_air, I think) to make the new one.
> > >
> > > Best wishes
> > >
> > > Jonathan
> >
> > ----- End forwarded message -----
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> ------
> Alison Pamment Tel: +44 1235 778065
> NCAS/Centre for Environmental Data Archival Email:
> alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Oxford, Didcot, OX11 0QX, U.K.
Received on Tue May 12 2015 - 08:03:26 BST
