The time elapsed in hours between the specified sun angle from 90 degree in am and pm. +ve above the horizon, -ve below the horizon.

dayLength(doy, lat, angle = -6)

Arguments

doy

day of year number

lat

latitude of site (deg)

angle

angle to measure time between, such as twilight (deg). angular distance between 90 deg and end of twilight - altitude of sun. +ve up, -ve down.