On the Rayleigh-Scattering Optical Depth of the Atmosphere

Abstract Hoyt's(1977) and Frohlich and Shaw's(1980) attempts to revise Rayleigh-scattering optical depths, using Raman-free depolarization ratios, are incorrect (see Young, 1980). King's (1923) formula for the anisotropy correction requires that the rotational Raman light be included in the depolarization measurement. Recent depolarization data show that the scattering optical depths for dust-free air are only ∼1% smaller than those used by Elterman (1968) and Penndorf (1957). Measured extinction values appreciably below standard Rayleigh values indicate systematic errors in measurement or reduction methods, not errors in the Rayleigh tables.