Absolute Spectral Measurements of Direct Solar Ultraviolet Irradiance with a Brewer Spectrophotometer
Bais, A. F.
[abstract] A methodology for the absolute calibration of spectral measurements of direct solar ultraviolet radiation, performed with a Brewer spectrophotometer is presented. The method uses absolute measurements of global and diffuse solar irradiance obtained practically simultaneously at each wavelength with the direct-Sun component. On the basis of this calibration, direct-Sun spectra, measured over a wide range of solar zenith angles at a high altitude site, were used to determine the extraterrestrial solar spectrum by applying the Langley extrapolation method. Finally this spectrum is compared with a solar spectrum derived from the airborne tunable laser absorption spectrometer 3 Space Shuttle mission, showing an agreement of better than ±3%.
[keywords] Direct-Sun spectra; Extraterrestrial spectrum; Solar ultraviolet