Calculates daylengths at a given period of the year (R.J. Reader & K. Phelps).
||Latitude at which the daylength is to be calculated, positive for northern hemisphere and negative for southern hemisphere; default 52.205 N (Wellesbourne)|
||Days of year for which daylengths are required|
||Calculated daylengths in hours|
DAYLENGTH calculates a set of daylengths at a given latitude. The numbers of the days during the year for which the daylengths are required should be specified, in a variate, using the
DAYNUMBER parameter. The lengths will then be stored in the variate specified by the
DAYLENGTH parameter. The latitude is defined by the
LATITUDE option, by default
LATITUDE=52.205 which is the latitude of Wellesbourne.
The formula by which the daylengths is calculated is given in Sellers (1965).
If either the
DAYNUMBER or the
DAYLENGTH variate is restricted, the calculations will be done only for the units not excluded by the restriction.
Sellers W.D. (1965). Physical Climatology. University of Chicago Press, Chicago, Illinois.
Commands for: Calculations and manipulation.
CAPTION 'DAYLENGTH example'; STYLE=meta VARIATE Dayno; !(1...31); DECIMALS=0 DAYLENGTH [LATITUDE=52.205] DAYNUMBER=Dayno; DAYLENGTH=Daylength CALCULATE Sunset = 12 + Daylength / 2 CALCULATE Sunrise = 12 - Daylength / 2 CAPTION 'Sunrise and Sunset times for January at Wellesbourne,UK.' PRINT Dayno,Sunrise,Sunset; DECIMALS=2