The Extinction-to-Backscatter Ratio of Tropospheric Aerosol: A Numerical Study

Abstract

An adequate estimation of the aerosol extinction-to-backscatter ratio S is important for solving the underdetermined single scattering lidar equation and for investigating the climate impact of aerosols. In this study, the extinction-to-backscatter ratios for the Nd:YAG wavelengths are calculated for continental, maritime, and desert aerosols; the corresponding aerosol components are varied within the expected natural variabilities of the particle number mixing ratios. For continental aerosol, S increases with the relative humidity f from 40 to 80 sr. For maritime aerosol, the extinction-to-backscatter ratios lie between 15 and 30 sr for 355 and 532 nm and between 25 and 50 sr for 1064 nm. The desert aerosol exhibits a weak dependence of S on f and ranges between 42 and 48 sr for 355 nm and between 17 and 25 sr for 532 and 1064 nm. For practical applications, the calculated values of S are fitted by a power series expansion with respect to their dependence on f.