The function calculates the zenith angle, the location of the sun as an angle (in degrees) measured from vertical (Campbell and Norman 1998) .

zenith_angle(doy, lat, lon, hour, offset = NA)

Arguments

doy

numeric day of year (1-366). This can be obtained from standard date via day_of_year.

lat

numeric latitude (decimal degrees).

lon

numeric longitude (decimal degrees).

hour

numeric hour of the day.

offset

numeric the number of hours to add to UTC (Coordinated Universal Time) to get local time (improves accuracy but not always necessary). Optional. Defaults to NA.

Value

numeric zenith angle (degrees)

References

Campbell GS, Norman JM (1998). Introduction to environmental biophysics, 2nd ed. edition. Springer, New York. ISBN 0387949372.

Examples

  zenith_angle(doy  = 112, 
               lat  = 47.61, 
               lon  = -122.33, 
               hour = 12)
#> [1] 35.71846