Dear Charles,
I think the standard name you are considering is appropriate for your
data. Downwelling shortwave flux includes both diffuse and direct
beam, and the diffuse includes everything not direct (i.e., it includes
stuff that got reflected upward by the surface). As I recall, "net" is
used when considering the difference between downwelling and upwelling
components. Here you consider only the "downwelling" component (even if
some of it traversed an upward path at some point before arriving at the
surface), so "net" is not what is meant.
I hope someone else will read this and disagree if I've said anything
incorrect.
Karl
On 5/6/13 9:18 AM, Charles Paxson wrote:
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
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