The Langley plot technique is a useful and well-known method for estimating atmospheric spectral extinction and/or the exoatmospheric solar spectral irradiance from ground-based spectroradiometer observations. This paper addresses the problem of detecting and assessing the bias of temporal optical depth variations with regard to retrieving the spectral solar constant (zero-airmass spectral solar irradiance) and instantaneous optical depth via the Langley method. The results of data simulations reveal that a number of possible forms of temporal optical depth variations can severely bias Langley plot estimates of optical depth and zero-airmass solar irradiance while yielding nearly straight Langley plots. Analyses of many spectroradiometer data sets reveal that the error in the determination of the zero-airmass solar irradiance is almost always significantly greater than the statistical uncertainty obtained from the Langley plot fit. This error can be estimated if the magnitude of the optical depth variation over the observation period is known.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Effects of Temporal Variations in Optical Depth on the Determination of the Optical Depth and Solar Constant from Solar Photometry
J. A. Reagan
I. C. Scott-Fleming
B. M. Herman
- American Meteorological Society