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Dear Deborah,
Thank you and your colleagues for the comments. I delayed my reply
because I wanted to carefully consider all the suggestions. One
challenge I grappled with in crafting these new standard names and
their definitions was how to find the right balance on the amount of
detail since observation data typically involves a lot of auxiliary
information. I tried to be only as specific as necessary which is of
course subjective.
On Wed, Sep 26, 2012 at 8:25 PM, Deborah Smith <smith@xxxxxxxxx> wrote:
> 1. For the platform and sensor look angle as written, nadir is defined as
> pointing towards the center of the Earth. We question whether this is
> appropriate for all cases, as many satellites are flown with nadir pointing
> toward the closest place on Earth, so that the nadir look has an incidence
> angle of 0. (geodetic vs. geocentric pointing). We suggest separate
> geodetic and geocentric look angle definitions to reduce confusion, such as
> sensor_look_angle_geocentric and sensor_look_angle_geodetic.
I agree that mentioning Earth center is misleading but I also haven't
seen a lot of documentation where geocentric or geodetic pointing is
clearly stated. Here's a rewrite of the platform_look_angle without
mentioning the Earth:
"
"platform" refers to the vehicle from which observations are made e.g.
airplane, ship, or satellite. Platform look angle is the angle between the
line of sight from the platform and the direction straight vertically down.
Zero look angle means looking directly beneath the platform.
"
Is this acceptable? I think it conveys enough information to clearly
describe the data.
> 2. There is only a
> linear_term_of_spectral_radiance_correction_due_to_intercalibration and a
> constant_term_of_spectral_radiance_correction_due_to_intercalibration.
> Many microwave radiometers have quadratic (or higher order) terms in the
> calibration and subsequent calibration corrections. We suggest adding more
> names.
I will add a name for the quadratic term. Perhaps the CF folks will
have a better suggestion how to deal with unlimited number of possible
polynomial terms in such correction formulas.
> 3. Azimuth angle definitions need to be clearer (see suggested changes in
> bold below). We would like to be sure that the definition is unambiguous.
Agree, the changes are accepted.
> 4. The definition for sensor_band_central_wavenumber does not say whether
> the first moment of the band's normalized spectral response function is
> averaged over wavelength or frequency. One can't invert wavelength and
> wavenumber if not calculated correctly.
This was intentionally left out because I think the standard name is
not the place for that information. An international project I
participate in debated exactly the same issue a few months ago and it
turned out that several member agencies used either different formulas
or same formulas with different coefficients. Does this mean that we
should have different standard names for all these possibilities? I
don't think so. Ed Armstrong is the original proposer of this name so
I leave to him the final decision.
-Aleksandar
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