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On Mon, 26 Sep 1994, Unidata User Support wrote:
> Solar noon for any location is a constant and may be calculated
> using the following information. Solar noon is at 1200 local
> standard time on a particular central time longitude. The
> central time longitudes are 75W, 90W, 105W, 120W, and 135W. For
> every degree of longitude away from the central time longitude,
> the solar time changes by four minutes. Eastward of the central
> longitude, the time of solar noon is earlier; westward, the time
> of solar noon is later.
>
> For example, if your station is at 96W longitude, the time of
> solar noon is 12:24 local standard time. If your station is at
> 85W longitude, the time of solar noon is 11:40 local standard
> time.
>
Not actually that simple. Doesn't it turn out that this time is also
dependent on the time of the year since a day is not 24 hours long but
longer or shorter depending on distance from sun. So, on any given day,
even at 75 W, solar noon may not be at noon. In fact, it can be as much
as 16 minutes longer or shorter than noon. Whether that is really
IMPORTANT to the idea of UV forecasts (ie, whether +/- 16 minutes is an
issue) is not clear.
Russ De Souza
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