Dear Andreas
I see there is a quantity named relative_sensor_azimuth_angle which is not the
same as your quantity, but confusion is possible! Therefore a name for your
quantity should include "solar" somewhere in it to clarify this, I suggest,
not just "relative azimuth angle". CF standard names are often descriptions,
so maybe it would be reasonable to call it difference_between_sensor_and_solar_
azimuth_angles. We have other stdnames containing "difference_between_X_and_Y".
Then in the definition you could say that the difference of angle is taken
either clockwise or anticlockwise, whichever is smaller, so that the angle is
no more than 180 degrees and is unsigned - have I understood that properly?
Best wishes
Jonathan
----- Forwarded message from Andreas Hilboll <lists at hilboll.de> -----
> Date: Mon, 17 Aug 2015 16:11:27 +0200
> From: Andreas Hilboll <lists at hilboll.de>
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] New standard name: angle between solar and sensor
> azimuth
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
> Thunderbird/31.8.0
>
> Hi all,
>
> a common quantity in satellite remote sensing of atmospheric composition
> is the so-called 'relative azimuth angle', which in that community
> refers to the difference of solar azimuth and sensor azimuth. However,
> relevant for the radiative transfer simulations is not the actual
> difference solar_azim - sensor_azim, but rather
>
> raa = abs(solar_azim - sensor_azim) [where abs(solar_azim -
> sensor_azim) < 180]
> 360 - abs(solar_azim - sensor_azim) [otherwise]
>
> I would like to propose this quantity to be included in the CF standard
> names, but am unsure how to a) name it [*] and b) describe it [**].
>
> Any ideas?
>
> Cheers,
> Andreas.
>
>
> [*] the 'relative_...' commonly used in satellite remote sensing of
> trace gases seems to be un-fit for CF, because there
>
> relative_sensor_azimuth_angle is the difference between the viewing
> geometries from two different sensors over the same observation
> target. It is the difference between the values of two quantities
> with standard name sensor_azimuth_angle.
>
> [**] I haven't yet seen formulas in the CF standard name definitions ...
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----- End forwarded message -----
Received on Mon Aug 17 2015 - 11:03:02 BST
