[CF-metadata] new standard names: day, night, and day/night terminator area_fractions

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 7 Jan 2014 15:09:39 +0000

Dear Randy

> what about area_fraction_defined_by_solar_zenith_angle ?
>
> "defined_by" exists in a couple of other standard names.

That's a good idea. I *almost* like it! In fact all the stdnames with this
phrase have ocean_mixed_layer_thickness_defined_by_X. This is almost the same
situation, but it doesn't seem exactly the same to me. The ocean ML is a
a distinct concept qualitatively; the defined_by_X says precisely how it is
defined quantitatively, in some cases using a (non-spatiotemporal) coordinate
value as we are in the present case.

In this case, we are not defining area_fraction. We are specifying an area_
fraction for a particular value of something else. I think defined_by would
be just right if the stdname was area_fraction_of_night_defined_by_solar_
zenith_angle. That would be exactly analogous to the ML case, I feel; the
night area fraction is a recognisable concept, but it needs to be defined
precisely. We could include defined_by if we reverted to three stdnames, as
Randy had proposed, area_fraction_of_X_defined_by_solar_zenith_angle, where
X is day, night or twilight (if that's the right word), and the defined_by
phrase is a signal that one shouldn't assume what day or night means without
checking the bounds provided for the zenith angle.

We already have a generic standard name of area_fraction. This is expected to
have a (string-valued auxiliary) coordinate of area_type, as it stands. We
could allow it alternatively to have a coordinate of solar_zenith_angle.
There would be no indication of what it depended on in the standard name.

If we want to indicate that, what about
area_fraction_with_given_solar_zenith_angle
That's another variation on the theme!

Best wishes

Jonathan
Received on Tue Jan 07 2014 - 08:09:39 GMT