Two types of sunphotometric measurement are considered in this study: direct-Sun irradiance and diffuse-sky radiance. Based on CIMEL CE318 Sun–sky radiometer characteristics, we introduce a gain-corrected solid angle that allows interconverting calibration coefficients of these two types of measurement, thus realizing a “vicarious” radiance calibration. The accuracy of the gain-corrected solid angle depends on the number of available historical calibration records. The method is easy to use, provided that at least one laboratory calibration has been made previously. Examples coming from three distinct CE318 versions belonging to the AERONET/PHOTONS network are presented to provide details on the vicarious calibration method and protocols. From the error propagation analysis and the comparison with laboratory results, the uncertainty of the vicarious radiance calibration is shown to be comparable with the laboratory one, e.g., 3%–5%.
© 2008 Optical Society of America
Atmospheric and Oceanic Optics
Original Manuscript: October 10, 2007
Revised Manuscript: January 25, 2008
Manuscript Accepted: January 28, 2008
Published: March 21, 2008
Zhengqiang Li, Luc Blarel, Thierry Podvin, Philippe Goloub, Jean-Pierre Buis, and Jean-Philippe Morel, "Transferring the calibration of direct solar irradiance to diffuse-sky radiance measurements for CIMEL Sun-sky radiometers," Appl. Opt. 47, 1368-1377 (2008)