day length calculations

Michelle Geary-Mallett ez045518 at
Fri Sep 8 10:52:01 EST 1995

amanda braley (braley at wrote:
: Does anybody know of or have a basic (or similar) computer model that
: will calculate the hours of daylight at any given latitude? I'm 
: working on a photoperiod project for which knowing the weekly 
: average hours of daylight at the various latitudes from which the 
: stock plants were collected would be usefull.  I have a table of 
: sunrise and sunset times, from which I could painstakingly calculate 
: the hours of daylight myself, but I was hoping somebody might have been
: clever enough to write a little model to do this for me.

: Sincerely,

: Amanda Braley
: Staff Research Associate
: University of California
: Riverside, CA 92521
: braley at

Hey Amanda!

This is a little indirect but...Paul Rich's CANOPY program must have that 
information/those calculations within it...because when you use the 
program, you give it the latitude and it assesses (given the canopy 
inputs) the incoming PFD for every day (more or less) at that location 
across the year.

I think Paul Rich is (was?) at Livermore Lab.  Bob has a copy of this 
program, as does Susan Ustin.

How's Riverside going?



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