| Charles,
The definitions also need specifications of how to indicate a threshold if one is used. The text for the surface_snow_binary_mask is:
The threshold must be specified by associating a coordinate variable or
scalar coordinate variable with the data variable and giving the
coordinate variable a standard name of surface_snow_area_fraction. The
values of the coordinate variable are the threshold values for the
corresponding subarrays of the data variable.
Looking at the current version of the standard name table, I found these names that might serve.
atmosphere_number_content_of_aerosol_particles (it's far from ideal, but it's the only one that includes all aerosols)
I guess this points up another issue. There are no standard names that relate to generalized dust. There are dust_dry_aerosol and dust_ambient_aerosol standard names. There are no standard names that use the word smoke. I was concerned about the question of thresholds, but I think there will need to be better definitions of all the terms used in these mask standard names. As an example, here's the definition for atmosphere_number_content_of_aerosol_particles:
"Content" indicates a quantity per unit area. The "atmosphere content"
of a quantity refers to the vertical integral from the surface to the
top of the atmosphere. For the content between specified levels in the
atmosphere, standard names including content_of_atmosphere_layer are
used. "Aerosol" means the suspended liquid or solid particles in air
(except cloud droplets).
I'm not qualified to speak on definitions of these terms, so I'll defer to the experts on this. The thresholds question could be answered by stating something along the lines of:
A threshold may be specified by associating a coordinate variable or scalar coordinate variable with the data variable and giving the coordinate variable a standard name that specifies the quantity used for determining the threshold. The values of the coordinate variable are the threshold values for the corresponding subarrays of the data variable. Sorry to keep stirring the pot.
Grace and peace,
Jim
Dear Jonathan and Jim,
I have seen your last and recent words on the mask proposals, and
I have incorporated your comments. I believe we are all in
agreement, and thank you for your work. I have written out the
proposed variables and definitions below according to our latest
agreement. Please let me know the procedure to formally finish
the proposal process for these four new mask standard names.
Sincerely,
Charles Paxson
aerosol_binary_mask: X_binary_mask
has 1 where condition X is met, 0 elsewhere. 1 = aerosols present, 0 = aerosols absent. Note that if no threshold is
supplied, the binary mask is 1 if there is any non-zero amount of
aerosol.
smoke_binary_mask:
X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 =
smoke present, 0 = smoke absent. Note that if no threshold is supplied, the binary mask is 1
if there is any non-zero amount of smoke.
dust_binary_mask:
X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 =
dust present, 0 = dust absent. Note that if no threshold is supplied, the binary mask is 1
if there is any non-zero amount of dust.
cloud_binary_mask:
X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 =
cloud present, 0 = cloud absent (clear). Note that if no threshold is supplied,
the binary mask is 1 if there is any non-zero amount of cloud
On 05/21/2013 05:25 PM, Jonathan Gregory wrote:
Dear Charles
Thank you for your email, and the subsequent one to Jim. In my earlier posting
I was not particularly arguing against the proposal, but I thought the
question should be asked. Evidently it is your intention that quantities with
these names should indeed be regarded as comparable. That is OK. If at some
point there arises a need for more specifically defined binary masks, other
standard names could be proposed for them.
You propose to include a nominal threshold of zero, indicating that any amount
of cloud etc. constitutes "presence". I think we could avoid that need, and
the related need to introduce standard names for the quantities in which the
threshold was set, by stating in the definition that if no threshold is
supplied, the binary mask is 1 if there is any non-zero amount of cloud etc.
Best wishes
Jonathan
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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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