Solar

What we call “current solar radiation” is technically known as Global Solar Radiation, a measure of the intensity of the sun’s radiation reaching a horizontal surface. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measure of the amount of solar radiation hitting the solar radiation sensor at any given time, expressed in Watts/sq. meter (W/m2).

Sunshine used interchangeably with the more precise term bright sunshine, when the sun casts an obvious shadow. The World Meteorological Organization defines sunshine as solar direct irradiance exceeding 120 W/m2.

Sunshine Duration

The length of time for which the sun casts an obvious shadow. The threshold tolerance for bright sunshine (based on World Meteorological Organization) is direct irradiance of 120 W/m plus or minus 20%.