Cosine of the Solar Zenith Angle

The Cosine of the Solar Zenith Angle is the cosine of the angle between the Sun and directly overhead during daylight hours. It is a key component of calculating mean radiant temperature from radiation.

Here 2 methods are presented: one takes the Cosine of the Solar Zenith Angle Instantly and one is designed to calculate the Solar Zenith Angle over a forecasting system time step.

There is a difference in output values of both methods, but once these values are used to calculate the radiant heat temperature in either UTCI or WBGT, the difference in their heat index outputs is, in average, 0.004 degrees Celsius.

more information: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL066868

How To Use

Cosine Solar Zenith Angle Instantaneous

Inputs are h (hour), latitude (in degrees), longitude (in degrees), y (year), m (month) and d (day).

It returns the average of cosine of the solar zenith angle in degrees.

calculate_solar_zenith_angle(h, lat, lon, y, m, d)

Cosine Solar Zenith Angle Integrated

Inputs are latitude (in degrees), longitude (in degrees), y (year), m (month), d (day), h (hour), tbegin (offset in hours from forecast time to begin of time interval for integration) and tend (offset in hours from forecast time to end of time interval for integration).

It returns the average of cosine of the solar zenith angle during interval in degrees.

calculate_cos_solar_zenith_angle_integrated(lat, lon, y, m, d, h, tbegin, tend)

Interpret the Output

The maximum value is 0.9 the values should range between 0 and 0.9.