fetch3.nhl_transpiration.NHL_functions.calc_zenith_angle

calc_zenith_angle(doy, lat, long, time_offset, time_of_day, zenith_method='CN')

Calculates the solar zenith angle, based on Campbell & Norman, 1998.

Also has options for 2 alternate methods: use a constant zenith angle of 0 (i.e. pretend the sun is always directly overhead), or replicate the results of the FETCH2 NHL code (which is missing an adjustment for longitude).

Parameters:

• doy (int) – Day of year (Ordinal day, e.g. 1 = Jan 1)

• lat (float) – Latitude

• long (float) – Longitude (Needs to be negative for deg W, positive for deg E)

• time_offset (int) – Time offset [in hours] for local standard time zone, e.g, for Pacific Standard Time, time_offset = -8

• time_of_day (float) – Time of day (hours) in local standard time

• zenith_method (str) –

  Method to use for the calculations. Options are:

  • ”CN” - Campbell & Norman 1998

  • ”constant” - constant zenith angle of 0

  • ”fetch2” - replicate the results of the FETCH2 NHL code

• Note (Be sure that time of day and time offset are in local standard time, not daylight savings) –

Returns:

zenith_angle_deg

Return type:

zenith angle of the sun [degrees]