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For a plane-parallel atmosphere, the airmass factor is simple to determine if one knows the solar zenith angle θ: m = 1/cos(θ). As time passes, the Sun moves across the sky, and therefore θ and m vary according to known astronomical laws. Direct solar radiation as a function of secant of solar zenith angle at Niamey, Niger. December 24, 2006.
The solar constant is an average of a varying value. In the past 400 years it has varied less than 0.2 percent. [2] Billions of years ago, it was significantly lower. This constant is used in the calculation of radiation pressure, which aids in the calculation of a force on a solar sail.
A pyranometer (from Greek πῦρ (pyr) 'fire' and ἄνω (ano) 'above, sky') is a type of actinometer used for measuring solar irradiance on a planar surface and it is designed to measure the solar radiation flux density (W/m 2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm.
Solar radiation maps are built using databases derived from satellite imagery, as for example using visible images from Meteosat Prime satellite. A method is applied to the images to determine solar radiation. One well validated satellite-to-irradiance model is the SUNY model. [38] The accuracy of this model is well evaluated.
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 ...
It is calculated as the fraction of the actual total solar radiation on the surface of the Earth during a certain period over the theoretical maximum (i.e., clear sky) radiation during the same period. [1] [2] The clearness index is a dimensionless quantity and can vary from 0 (sky is completely covered) to 1 (perfectly sunny). [3]
The radiative transfer equation is a monochromatic equation to calculate radiance in a single layer of the Earth's atmosphere. To calculate the radiance for a spectral region with a finite width (e.g., to estimate the Earth's energy budget or simulate an instrument response), one has to integrate this over a band of frequencies (or wavelengths ...
The flux density of the incoming solar radiation is specified by the solar constant S 0. For application to planet Earth, appropriate values are S 0 =1366 W m −2 and α P =0.30. Accounting for the fact that the surface area of a sphere is 4 times the area of its intercept (its shadow), the average incoming radiation is S 0 /4.