Dear Heather,
Thank you for your query. I have looked back at the discussion. Four names were proposed in all, and towards the end of the discussion the names and definitions had been suggested as follows:
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.
I think the names themselves were agreed, but there was an unresolved question (raised by Jim Biard
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056560.html) of how to specify the value of the threshold if a value other than zero was used to assign a mask value of one. We would need to provide advice on this in the definitions of the proposed standard names.
The only existing example of a binary mask standard name where a threshold is also used is surface_snow_binary_mask defined as follows:
' "X"_binary_mask" has 1 where condition X is met, 0 elsewhere. The value is 1 where the snow cover area fraction is greater than a threshold, and 0 elsewhere. 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.'
In the case of cloud_binary_mask, we do already have an existing standard name of cloud_area_fraction, so we could take an approach very similar to the snow mask name and combine it with the proposed definition of the new name:
cloud_binary_mask (canonical units '1'): ' "X"_binary_mask" has 1 where condition X is met, 0 elsewhere. The value is 1 where the cloud cover area fraction is greater than a threshold, and 0 elsewhere. if no threshold is supplied, the binary mask is 1 if there is any non-zero amount of cloud. if a threshold is supplied, it 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 cloud_area_fraction. The values of the coordinate variable are the threshold values for the corresponding subarrays of the data variable.'
If there are no objections to this approach, then I think cloud_binary_mask can be accepted for addition to the standard name table.
Regarding the other names, as Jim pointed out in the original discussion, it is less clear how thresholds could be supplied if needed. However, we can discuss those separately and they need not delay acceptance of the cloud name.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
From: Heather Brown - NOAA Affiliate [mailto:heather.brown at noaa.gov]
Sent: 30 April 2015 14:09
To: CF Metadata List
Cc: Daniel Wunder - NOAA Affiliate; Pamment, Alison (STFC,RAL,RALSP)
Subject: Status of cloud_binary_mask?
CF folks,
I see the status of the cloud_binary_mask has been in discussion since June 2013.?
I would like to propose a decision be made upon this standard_name.? It would compliment the other X_binary_mask standard_names.
Term:?cloud_binary_mask
Unit: 1
Unit ref:
http://vocab.ndg.nerc.ac.uk/term/P061/current/UUUU
AMIP:
GRIB:
X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = cloud present, 0 = cloud absent (clear).
Thank you for your consideration,
Heather
?
?
Heather Brown
Meteorological Archive Specialist - STG - Federal?Government Contractor
?
NOAA's National Centers for Environmental Information (NCEI)
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Asheville, NC 28801-5001 USA
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Received on Thu Apr 30 2015 - 08:45:39 BST
