Bias in a solar constant determination by the Langley method due to structured atmospheric aerosol: comment.
A recent article by Schotland and Lea [Appl. Opt. 25, 2486 (1986)] discusses the errors in radiometer calibration by the Langley method and the detail required for very precise work. Their numerical methods on aerosol air mass can be simplified for use in the calibration of the worldwide sunphotometer network by using geometric considerations, assuming aerosol scale heights of ~1 Km and using the apparent solar zenith angle at the instrument as the independent variable in these formulas, so that refraction effects are incorporated. By using multiple-pass Langley analyses the errors due to air mass assignments can be reduced significantly.
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