A new procedure is presented for determining in situ the solar calibration constant, i.e., the Sun-sky radiometer counts for a direct normal solar flux extrapolated to the top of the atmosphere. The method makes use of a modified version of the Langley plot based on the use of an inversion code of column-integrated aerosol size distribution, and it is ordinarily applied to calibrate Prede Sun-sky radiometers. To analyze how such an in situ method can work accurately, the technique has been applied to a five-month dataset obtained from measurements taken in Rome, Italy, by a Prede Sun-sky radiometer from 22 April to 5 November 2001. The precision of the in situ method has been estimated to within 1–2.5%, depending on the wavelength.
© 2004 Optical Society of America
Original Manuscript: May 7, 2003
Revised Manuscript: October 14, 2003
Published: January 20, 2004
Monica Campanelli, Teruyuki Nakajima, and Bruno Olivieri, "Determination of the solar calibration constant for a sun-sky radiometer: proposal of an in-situ procedure," Appl. Opt. 43, 651-659 (2004)