Dear Randy, Jonathan, and all,
I agree that the hybrid choice with "twilight" rather than "terminator,
is clearest.
Just to cover all the options (or maybe to revisit a suggestion I missed
earlier), could new area_type(s) be defined -- day, night, twilight --
and then we could just use the standard name area_fraction with, for
example, a cell_methods of "area: sum where day over all_area_types".
This would not explicitly indicate the zenith angle is used to define
the region of day, but perhaps that could be implied by defining
"solar_zenith_angle" coordinate bounds just as we would under the hybrid
method.
Anyway, I agree that the hybrid choice would still be easier for most to
interpret.
best regards,
Karl
On 1/10/14 4:52 AM, Randy Horne wrote:
> Dear Jonathan:
>
> good point on ?area?.
>
> ?twilight? is fine.
> I?m good with your preference of [a hybrid of (1) and (2) (i.e. area_fraction_of_night_defined_by_solar_zenith_angle, area_fraction_of_day_defined_by_solar_zenith_angle, area_fraction_of_twilight_defined_by_solar_zenith_angle)]
>
>
> very respectfully,
>
> randy
>
>
>
> On Jan 10, 2014, at 6:50 AM, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
>
>> Dear Randy
>>
>> Thanks for this useful summary.
>>
>> You favour
>>
>>> (3) make use of existing area_fraction names and qualify the type of area_fraction with one or more coordinate variable(s) and accompany use of cell_methods attribute
>>>
>>> pros: no need for an additional standard name, unambiguous, flexible (allows for a variety of yet-to-be-defined quantities), one variable can hold all three values
>>> cons: modification to the definition of area_fraction required, more complex than other options
>>> Later comment:
>>> Option (3) requires separate variables for day, night, and terminator region because a variable has a single cell_methods attribute, and cell_methods is used to specify the areal extent.
>> I don't think so, actually. cell_methods would have "area: mean" in this case,
>> I think, because you can consider the area_fraction to be the mean over the
>> cell of a binary variable (0 or 1). I'm not sure if that's best, but it is
>> definitely not "point", and "sum" isn't appropriate because it's not extensive.
>> The bounds would belong to the coordinate variable of solar_zenith_angle.
>>
>> I would be content with (3) but on the whole I prefer
>>
>>> (4) a hybrid of (1) and (2) (i.e. area_fraction_of_night_defined_by_solar_zenith_angle, area_fraction_of_day_defined_by_solar_zenith_angle, area_fraction_of_terminator_region_defined_by_solar_zenith_angle)
>>>
>>> pros: very clear
>>> cons: new form of standard names containing area_fraction, 3 standard names where 1 can be made to work
>> I like this because it's very clear, as you say. It thus avoids the problem of
>>
>>> (1) add a type of area fraction consistent with current definition of existing area_fraction (i.e.. day_area_fracton, night_area_fraction, day_night_terminator_area_fraction)
>>>
>>> pros: clear, consistent with current use and definition of area
>>> cons: 3 standard names where 1 can be made to work
>> which doesn't point out so prominently that "day" and "night" have to be
>> given precise definitions. The discussion shows that (2) causes problems
>> because we can't find a form of words (so far) that everyone considers to
>> convey the right notion.
>>
>>> (2) add a new grammatical form of a standard_name containing area_fraction i.e.. area_fraction_X_solar_zenith_angle, area_fraction_for_solar_zenith_angle_within_bounds)
>>>
>>> A variety of options have been set forth for X, such as "of", "as a function of", "with", "defined_by", "with_given"
>>>
>>> pros: one standard name, one variable can hold all three values
>>> cons: new form of standard names containing area_fraction, options are either not particularly clear or violate (to varying degrees) conventions associated with existing standard names,
>> I'd be interested to know whether you consider "twilight" to be acceptable.
>> Wikipedia also gives "twilight zone" as a synonym for "terminator". I think
>> "twilight" goes better with "day" and "night" than "terminator" does.
>>
>> What do other people think about all the above?
>>
>> Best wishes
>>
>> Jonathan
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>
> ____________________________________
>
> Randy C. Horne (rhorne at excaliburlabs.com)
> Principal Engineer, Excalibur Laboratories Inc.
> voice & fax: (321) 952.5100
> url: http://www.excaliburlabs.com
>
>
>
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