Dear Gary
There are many existing standard names which use the phrase clear_sky for
a cloud-free area; to be consistent I would suggest clear_sky_area_fraction.
This is presumably 1-cloud_area_fraction.
I've got a couple of comments on "probably" names. Firstly, the definition of
"probably" is rather specific to the application, and it is not obvious to me
that this is a concept which would be comparable among datasets (which is the
main purpose of CF standard names). Secondly, it seems from the definition
that these are actually estimates, by a particular technique, of the clear-
sky and cloud area fractions. If so, they aren't distinct geophysical
quantities, so they shouldn't have their own standard names. The method of
measurement could instead be indicated by some other attribute, such as the
long_name.
Best wishes
Jonathan
----- Forwarded message from Gary Meehan <gmeehan at aer.com> -----
> I would like to propose three new standard names in support of the
> GOES-R Advanced Baseline Imager Clear Sky Mask
> algorithm. They are as follows:
>
> standard_name: clear_area_fraction
>
> Definition: "X_area_fraction" means the fraction of horizontal area
> occupied by X.The clear area fraction is for the whole
> atmosphere column, as seen from the surface or the top of the
> atmosphere. "clear" means that the target pixel is completely
> clear. In addition, the NxN pixels centered on the target pixel are
> indicated to have a low degree of spatial heterogeneity.
>
> Canonical units: None
>
> ------------------------------------------------------------------
>
> standard_name: probably_clear_area_fraction
>
> Definition: "X_area_fraction" means the fraction of horizontal area
> occupied by X.The probably clear area fraction is for
> the whole atmosphere column, as seen from the surface or the top of
> the atmosphere. "Probably clear" means that the
> target image pixel is identified as being clear. In addition, the
> NxN pixels centered on the target pixel are indicated to have a high
> degree
> of spatial heterogeneity. Also, one or more adjacent pixels are
> identified as cloudy. The target pixel is therefore
> considered to be possibly cloud-contaminated, and thus probably clear.
>
> Canonical units: None
>
> -------------------------------------------------------------------
>
> standard_name: probably_cloudy_area_fraction
>
> Definition: "X_area_fraction" means the fraction of horizontal area
> occupied by X.The probably cloudy area fraction is for
> the whole atmosphere column, as seen from the surface or the top of
> the atmosphere. "Probably cloudy" means that a cloud
> was detected in the target image pixel, but likely contains a cloud
> edge. Since one or more neighboring pixels are clear, the
> target pixel is considered to be probably cloudy.
>
> Canonical units: None
>
>
> Sincerely,
>
> Gary Meehan
>
> --
> Gary Meehan
> Senior Staff Scientist
> Atmospheric and Environmental Research
> 131 Hartwell Avenue, Lexington, MA 02421-3126
> Tel (781) 761-2228 ? Fax (781) 761-2299
> e-mail:gmeehan at aer.com
>
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----- End forwarded message -----
Received on Wed Dec 04 2013 - 10:03:09 GMT
