Application of the SKYRAD Improved Langley plot method for the in situ calibration of CIMEL Sun-sky photometers.

The in situ procedure for determining the solar calibration constants, originally developed for the PREDE Sun-sky radiometers and based on a modified version of the Langley plot, was applied to a CIMEL instrument located in Valencia, Spain, not integrated into AERONET. Taking into account the different mechanical and electronic characteristics of the two radiometers, the method was adapted to the characteristics of the CIMEL instrument. The iterative procedure for the determination of the solar calibration constants was applied to a 3-year data set. The results were compared with the two sets of experimental calibration constants determined during this period using the standard Langley plot method. The agreement was found to be consistent with the experimental errors, and the method can definitely also be used to determine the solar calibration constant for the CIMEL instrument, improving its calibration. The method can be used provided the radiometer is previously calibrated for diffuse radiance using a standard lamp.

[1]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[2]  T. Nakajima,et al.  Determination of the solar calibration constant for a sun-sky radiometer: proposal of an in-situ procedure. , 2004, Applied optics.

[3]  O. Boucher,et al.  A satellite view of aerosols in the climate system , 2002, Nature.

[4]  María P. Utrillas,et al.  Aerosol size distributions and air mass back trajectories over a Mediterranean coastal site , 2004 .

[5]  Hugh D. Young,et al.  Statistical Treatment of Experimental Data. , 1963 .

[6]  M. P. Utrillas,et al.  Intercomparison of spectroradiometers and Sun photometers for the determination of the aerosol optical depth during the VELETA‐2002 field campaign , 2006 .

[7]  T. Nakajima,et al.  Retrieval of the optical properties of aerosols from aureole and extinction data. , 1983, Applied optics.

[8]  C. Gueymard.  Parameterized transmittance model for direct beam and circumsolar spectral irradiance , 2001 .

[9]  G. Shaw.  Error analysis of multi-wavelength sun photometry , 1976 .

[10]  B. Holben,et al.  Use of sky brightness measurements from ground for remote sensing of particulate polydispersions. , 1996, Applied optics.

[11]  Oleg Dubovik,et al.  Non‐spherical aerosol retrieval method employing light scattering by spheroids , 2002 .

[12]  Michael D. King,et al.  A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements , 2000 .

[13]  A. Drummond,et al.  Extraterrestrial solar spectrum , 1973 .

[14]  Alexander Smirnov,et al.  Cloud-Screening and Quality Control Algorithms for the AERONET Database , 2000 .