Ratio of aerosol backscatter to extinction coefficients as determined from angular scattering measurements for use in atmospheric lidar applications

Wavelength dependence as well as relative humidity dependence of aerosol extinction to backscatter ratio was examined. The extinction to backscatter ratio is essential in solving lidar signal and was estimated from aerosol size distribution and refractive index (which were derived from angular light scattering measurements) using the Mie scattering theory. The extinction to backscatter ratios were calculated for wavelengths of 355 nm, 532 nm, 694 nm and 1064 nm, the major laser wavelengths used for lidars, where the refractive indices were assumed to be constant with wavelength. p ]When relating the aerosol extinction ₁ to the backscatter ₁ with a functional form of _{1 1} k ₁, the exponentk ₁ was evaluated by the least square method and tabulated for the four wavelengths. The extinction to backscatter ratio defined asS ₁= ₁/ ₁ was calculated and their dependence on the wavelength and relative humidity was examined. Their dependence on the relative humidity is small whileS ₁ in the average takes the value of 66 (±17), 60 (±13), 52 (±13) and 42 (±11) for the wavelengths 355 nm, 532 nm, 694 nm and 1064 nm, respectively