Solar Radiation On Earth Surface

Solar radiation reaches earth s surface as 1 direct beam solar radiation 2 diffuse solar radiation and 3 reflected radiation which can be neglected.

Solar radiation on earth surface. Solar irradiance is the power per unit area received from the sun in the form of electromagnetic radiation as reported in the wavelength range of the measuring instrument. The sun is generally considered to produce a constant amount of power although there are small variances in the output energy depending on sunspot cycles with a surface intensity of expressed in units of power per unit area as the sun s rays spread into space this radiation becomes less and less intense as an inverse square law. The solar radiation that reaches the earth s surface without being diffused is called direct beam solar radiation. If the extraterrestrial solar radiation is 1367 watts per square meter the value when the earth sun distance is 1 astronomical unit then the direct sunlight at earth s surface when the sun is at the zenith is about 1050 w m 2 but the total amount direct and indirect from the atmosphere hitting the ground is around 1120 w m 2.

The solar constant g sc is a flux density measuring mean solar electromagnetic radiation solar irradiance per unit area. Atmospheric conditions can reduce direct beam radiation by 10 on clear dry days and by 100 during thick. It is measured on a surface perpendicular to the rays one astronomical unit au from the sun roughly the distance from the sun to the earth. The solar constant includes all types of solar radiation other than neutrinos not just the visible light.

It takes approximately eight minutes for solar radiation to reach the earth after leaving the sun s surface. Solar radiation at the earth s surface varies from the solar radiation incident on the earth s atmosphere. The solar irradiance is measured in watt per square metre w m 2 in si units solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment. This is called diffuse solar radiation.

The sum of the diffuse and direct solar radiation is called global solar radiation. The total radiation received from the sun of a horizontal surface at the level of the ground for a serene day is the sum of the direct and diffuse radiations.