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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Received on Thu May 09 2013 - 18:19:52 BST
