Atmospheric aerosol index of refraction and size-altitude distribution from bistatic laser scattering and solar aureole measurements

Abstract

The polarization and intensity of laser light scattered from a 500-m horizontal column of air was measured for angles from 8 degrees to 172 degrees . By photographing the sun's aureole, the intensity of sunlight scattered from a column of air between the earth and the sun was measured from 2 degrees to 12 degrees . These three simultaneous independent data sets were analyzed assuming single Mie scattering corrected for Rayleigh scattering. A regularized power law oversize distribution N(r) = N(O)/[1 + (r/a)(nu)] was used in the analyses. Typical parameters values obtained are a = 0.05 microm, nu = 3.5, and N(0) ~ 10(4) cm(-3). Although the laser and aureole techniques look at somewhat different volumes of air, under good vertical mixing conditions they are in quantitative agreement. The complex index of refraction of undisturbed aerosols, particles complete with liquid coatings, is found to be typically m(r) = 1.50 +/- 0.05, m(i) ~ 0.005.