Ken: Thanks .... good comment. In the definitions for the four
radiance quantities, I will replace: "outgoing" means emitted toward
outer space. with: "outgoing" means emitted or reflected toward
outer space.
very respectfully,
randy
----------------------------------------
From: "Kenneth S. Casey - NOAA Federal" <kenneth.casey at noaa.gov>
Sent: Wednesday, April 03, 2013 11:44 AM
To: rhorne at excaliburlabs.com
Cc: cf-metadata at cgd.ucar.edu, cf-satellite at unidata.ucar.edu
Subject: Re: [cf-satellite] Consistent standard_names for satellite derived
radiance quantities
Randy - I am not the expert on these definitions, but the word "emitted" is
used in each of them. Might be more appropriate to say "emitted or
reflected"??? Meaning, the radiance being measured at the TOA might be
reflected off a terrestrial surface, not emitted from that surface.
Ken
On Apr 3, 2013, at 11:28 AM, "rhorne at excaliburlabs.com"
<rhorne at excaliburlabs.com> wrote: Folks:
In the past few months there have been three standard_names proposed
related to radiance or irradiance quantities at the top of the atmosphere
derived from data sensed by a satellite. The proposals are as follows:
(a)
Message subject: cf-satellite Digest, Vol 29, Issue 1 from Peter Miu
standard_name: toa_spectral_irradiance with canonical units mW m-2 (cm-1)-1
Definition:
Irradiance which is relevant for any sensor measuring in the UV-VIS and
NIR. This parameter is reported by integrating over the whole sphere.
(b)
Message subject: cf-satellite Digest, Vol 29, Issue 1 from Peter Miu
standard_name: toa_outgoing_inband_radiance with canonical units mW m-2
sr-1
Definition: "outgoing" means emitted toward outer space; the radiance is
integrated over a discrete band.
(c)
Message subject: [CF-metadata] New Standard Names for Satellite Data from
Aleksandar Jelenak
Standard_name: toa_outgoing_spectral_radiance with canonical units mW m-2
sr-1 (cm-1)-1
Definition: "toa" means top of atmosphere; "outgoing" means emitted toward
outer space "spectral" means per unit wavenumber or as a function of
wavenumber. Radiance is the radiant power per unit area in a particular
direction per unit of solid angle.
The prefixes "toa" and "outgoing" identified in the CF standard name
guidelines are applicable.
The overarching consistency issue of the quantities revolves around their
units. For both radiance and irradiance, there are four types of
potentially reported quantities where the mappings between them is not
trivial, and, more specifically, not supported with a CF standard name
modifier or cell_method. The types of quantities are as follows with a
focus only on the contrasting characteristics (in a given direction per
unit area & per unit solid angle are omitted):
1) Power integrated over all wavelengths.
2) Power at a discrete monochromatic wavelength.
3) Power integrated over a discrete bandpass.
4) Power per unit wavelength integrated over a discrete bandpass
and normalized by the bandpass response function (i.e. the spectral
response of the sensor).
Given .
* The four types of radiance & irradiance quantities identified immediately
above.
* The need to conform with existing applicable CF standard name
conventions, specifically the prefixes "toa" and "outgoing".
* The fact that 2) & 4) immediately above are spectral quantities.
* The need to capture the frequency band associated with the
radiance/irradiance quantity for 3) & 4) immediately above.
. results in the following standard_names, and "strawman" definitions and
canonical units for the four radiance quantities. Note that we have
leveraged the work done by Peter and Aleksander.
++++++
#1
standard_name: toa_outgoing_radiance
Definition: "toa" means top of atmosphere. "outgoing" means emitted toward
outer space. This quantity is the radiant power per unit area in a given
direction per unit solid angle integrated over all wavelengths.
Canonical units: W m-2 sr-1
++++++
#2
standard_name: toa_outgoing_spectral_radiance
Definition: "toa" means top of atmosphere. "outgoing" means emitted toward
outer space. "spectral" means per unit wavenumber or as a function of
wavenumber. Radiant power per unit area in a given direction per unit solid
angle at a discrete monochromatic wavelength.
Canonical units: mW m-2 sr-1 (cm-1)-1
Note: A coordinate variable to capture the wavelength may be used.
***This quantity and its standard_name are identical to that proposed by
Aleksander. See c) above. ***
+++++
#3
standard_name: toa_outgoing_inband_radiance
Definition: "toa" means top of atmosphere. "outgoing" means emitted toward
outer space. "inband" means the radiance quantity is for a discrete
bandpass. This quantity is the radiant power per unit area in a given
direction per unit solid angle integrated over a discrete bandpass.
Canonical units: W m-2 sr-1
Note: A coordinate variable to capture the center wavelength, and
potentially, a boundary variable to capture the bandpass extents may be
used.
***This quantity and its standard_name are identical to that proposed by
Peter. See b) above. ***
+++++
#4
standard_name: toa_outgoing_inband_spectral_radiance
Definition: "toa" means top of atmosphere. "outgoing" means emitted toward
outer space. "inband" means the radiance quantity is for a discrete
bandpass. "spectral" means per unit wavenumber or as a function of
wavenumber. This quantity is the radiant power per unit area in a given
direction per unit solid angle per unit wavelength integrated over a
discrete bandpass and normalized by the bandpass response function.
Canonical units: mW m-2 sr-1 (cm-1)-1
Note: A coordinate variable to capture the center wavelength, and
potentially, a boundary variable to capture the bandpass extents may be
used.
+++++
There are analogous standard_name for the irradiance values. They are not
included in this email to keep the material in as "bite size chunks" as
possible in an effort to get some feedback.
very respectfully,
randy _______________________________________________
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Kenneth S. Casey, Ph.D.
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http://www.nodc.noaa.gov
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Received on Wed Apr 03 2013 - 15:06:22 BST
