Determination of Aerosol Extinction-to-Backscattering Ratio from Multiwavelength Lidar Observation

Abstract

We propose a method to determine the extinction-to-backscattering ratio (S1 parameter) in the troposphere from multiwavelength (355, 532, 756, and 1064 nm) lidar data. In our approach, reference profiles are prepared by using the wavelength dependence of the extinction coefficient as derived either from the sun photometer data or from the Mie calculation. By comparing these reference profiles with the profiles calculated using the conventional Fernald inversion method, the S1 parameter is determined for each wavelength. When a reasonable range is covered at 532 nm, this method makes it possible to determine the S1 parameters for shorter or longer wavelengths for which full range observation cannot be attained, due presumably to small laser power or limited detector efficiency. In addition, information about the vertical uniformity of aerosol properties can be derived from the S1 dependence of the difference between the reference and retrieved profiles.