A Redetermination of the Rayleigh Optical Depth and its Application to Selected Solar Radiation Problems

Abstract

Rayleigh optical depths are calculated for six standard atmospheres using the latest value of the depolarization factor (ρ_n = 0.0139). Present uncertainties in the Rayleigh optical depth of ±0.16% exist for the values calculated in this paper but the new values are 3.5–3.7% lower than previously reported values. As a consequence it is shown that previous aerosol optical depth or turbidity values from Volz sunphotometer measurements, for example, are reported with systematic errors 2–100% too low. The new Rayleigh optical depths are shown to largely explain the systematic differences between the various wavelength pair determinations of total ozone by the Dobson spectrophotometer. Other possible applications of the results of this paper are also indicated.