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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.
Solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment (joule per square metre, J/m 2) during that time period. This integrated solar irradiance is called solar irradiation, solar radiation, solar exposure, solar insolation, or insolation.
To make the first measurements of the visible and near-infrared solar irradiance with sufficient precision for future climate studies. Obtain daily measurements of solar spectral irradiance between 0.3 and 2 μm with a spectral resolution of at least 1/30, an accuracy of 0.03%, and long-term repeatability of better than 0.01%/yr.
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
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.
In radiometry, radiant exposure or fluence is the radiant energy received by a surface per unit area, or equivalently the irradiance of a surface, integrated over time of irradiation, and spectral exposure is the radiant exposure per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength.
Solar irradiance spectrum above atmosphere and at surface. The overall intensity of solar radiation is like that of a black body radiator of the same size at about 5,800 K. [1] As it passes through the atmosphere, sunlight is attenuated by scattering and absorption; the more atmosphere through which it passes, the greater the attenuation.
Solar irradiance spectrum at top of atmosphere, on a linear scale and plotted against wavenumber. The solar constant (G SC) measures the amount of energy received by a given area one astronomical unit away from the Sun. More specifically, it is a flux density measuring mean solar electromagnetic radiation (total solar irradiance) per unit