Dear cf-metadata community,
We have two questions arising from considering whether the CF-Metadata
/surface_downwelling_shortwave_flux_in_/air may be used as a standard
name for the GOES-R product: /Downward Shortwave Radiation.
/1) Does the "diffuse solar radiation incident on the surface"
specifically include radiation that resulted from surface reflection
then subsequent atmospheric scattering back down to the surface? This
is not spelled out in the standard definition.
2) What does "net downward" mean, i.e. does it mean total downward
radiation minus reflected radiation?
The following is the background that lead us to our questions:
The GOESR program will produce a product called "Downward Shortwave
Radiation", and the CF Meta Data database maintains a standard name
variable entitled "/surface_downwelling_shortwave_flux_in_/air". The
GOESR definition and the CF Metadata definitions are similar, and the
difference is in part that the CF Metadata definition includes the
sentence: "It does not mean 'net downward'." Clarifying this sentence
in the context of the GOESR definition will help us to decide whether to
adopt this name as a standard name.
The essential CF standard definition for
/surface_downwelling_shortwave_flux_in_/air is: Surface downwelling
shortwave is the sum of direct and diffuse solar radiation incident on
the surface. It does not mean "net downward".
The GOESR equivalent quantity is similar including both direct and
diffuse radiation with the additional second order component:
"/radiation that is reflected upward at the surface and subsequently
reflected back to the surface by the atmosphere/".
Our understanding is that the statement "It does not mean 'net
downward'.", precludes the reflected component as well as secondary
effects from the surface reflection.
Sincerely,
Charles
--
Charles Paxson
System Engineer
Atmospheric and Environmental Research (AER), Inc.
a Verisk Analytics Company
131 Hartwell Avenue, Lexington, MA 02421-3126
office: 781-761-2209
fax:781-761-2299
www.aer.com
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