Hi John,
The reason I didn't jump to respond to Alison's suggested change is that I viewed it as a correction of a typo that hadn't been spotted rather than a redefinition. In my book PAR (photosynthetically active radiation) - the wavelengths that may be utilised by plants for photosynthesis - has always been 400-700nm.
Cheers, Roy.
-----Original Message-----
From: John Graybeal [mailto:jbgraybeal at mindspring.com]
Sent: 13 May 2015 17:46
To: CF Metadata List
Subject: Re: [CF-metadata] New standard name request for FAPAR
I'm a little surprised no one else has commented on the plan to change all the photosynthetic radiation definitions. I expect you've all heard the purist view before, so I'll keep it short.
The obvious issue is that all files written with the previous definition in place -- of which there must be some, namely those who instigated the original definition -- will be henceforth misinterpreted by viewers of those files.
The generalized issue is that if it's possible for standard name definitions to change, one can never be sure what version of Standard Names the original producer of a file was using, or what definitions might have been in place (if any) in that version. One can review the entire history of definitions for a given standard name, but should we not avoid this ambiguity in the first place?
OK, that's my piece, I've said it, now we can all return to the existing "generally OK" practice.
John
On May 13, 2015, at 03:06, <alison.pamment at stfc.ac.uk> <alison.pamment at stfc.ac.uk> wrote:
> Dear Martin,
>
> Excellent, thank you. This name is now accepted for inclusion in the standard name table and will be added at the next update.
>
> Incidentally, I now realise that 17 existing names use the 300 - 700 nm definition of photosynthetic radiation. I will also update all of these to read "400 - 700 nm".
>
> In the next update of the standard name table I would like to include as many as possible of the names proposed by Randy Horne et al for the GOES-R satellite series. It is going to take 2-3 weeks at least to review all the relevant names so the next update will occur in the first half of June.
>
> 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: 12 May 2015 17:23
>> To: Pamment, Alison (STFC,RAL,RALSP); cf-metadata at cgd.ucar.edu;
>> j.m.gregory at reading.ac.uk
>> Subject: RE: [CF-metadata] New standard name request for FAPAR
>>
>> Dear Alison
>>
>> It sounds very good to me. No more remarks.
>>
>> best regards
>>
>> Martin
>> ________________________________________
>> From: alison.pamment at stfc.ac.uk [alison.pamment at stfc.ac.uk]
>> Sent: Tuesday, May 12, 2015 10:03 AM
>> To: Claverie, Martin (GSFC-6190)[Science Collaborator]; cf-
>> metadata at cgd.ucar.edu; j.m.gregory at reading.ac.uk
>> Subject: RE: [CF-metadata] New standard name request for FAPAR
>>
>> 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_vegetat
>> ion. 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_absorbe
>> d
>> _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_absorbe
>> d _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_absorb
>> e
>>> 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=&prop
>> os
>>>
>> erfilter=Claverie&descfilter=&unitfilter=&yearfilter=&filter+and+disp
>> lay=Fil
>>> ter.
>>>
>>> fraction_of_absorbed_photosynthetically_active_radiation (canonical
>> units
>>> 1)
>>>
>>> I agree with Jonathan that
>>>
>> fraction_of_surface_downwelling_photosynthetic_radiative_flux_absorbe
>> d
>>> _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_absorbe
>> d
>>>> _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.
>
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Received on Thu May 14 2015 - 01:20:27 BST
