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Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. It is also called sky radiation , the determinative process for changing the colors of the sky .
Diffuse horizontal irradiance (DHI), or diffuse sky radiation is the radiation at the Earth's surface from light scattered by the atmosphere. It is measured on a horizontal surface with radiation coming from all points in the sky excluding circumsolar radiation (radiation coming from the sun disk).
The first versions of SMARTS were developed by Dr. Gueymard while he was at the Florida Solar Energy Center. [2] [3] [4] The model employed a structure similar to the earlier SPCTRAL2 model, still offered by the National Renewable Energy Laboratory (), but with finer spectral resolution, as well as updated extraterrestrial spectrum and transmittance functions.
The global irradiance on a horizontal surface on Earth consists of the direct irradiance E e,dir and diffuse irradiance E e,diff. On a tilted plane, there is another irradiance component, E e,refl, which is the component that is reflected from the ground. The average ground reflection is about 20% of the global irradiance.
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by astronomical objects is generally not considered daylight.
Rayleigh scattering of sunlight in Earth's atmosphere causes diffuse sky radiation, which is the reason for the blue color of the daytime and twilight sky, as well as the yellowish to reddish hue of the low Sun. Sunlight is also subject to Raman scattering, which changes the rotational state of the molecules and gives rise to polarization ...
Managing solar radiation using aerosols or cloud cover would involve changing the ratio between direct and indirect solar radiation. This would affect plant life [ 43 ] and solar energy . [ 44 ] Visible light, useful for photosynthesis, is reduced proportionally more than is the infrared portion of the solar spectrum due to the mechanism of Mie ...
Similarly, diffuse solar radiation is calculated as the sum of all diffuse radiation (scattered from the atmosphere) originating from any visible (non-obscured) sky directions (see diffuse sky radiation). The sum of direct and diffuse components gives global radiation. These calculations require theoretical or empirical distributions of direct ...