High Spectral Resolution Lidar Measurements of Cirrus Cloud Optical Properties

Abstract

Lidar backscatter signals are generated by scattering from both molecules and particles. The spectral distribution of light scattered by molecules is Doppler-broadened by rapid, thermally induced, molecular motions. Light scattered by aerosols and cirrus particles is essentially unshifted because of the relatively slow Brownian motion of particles. Using this difference, the High Spectral Resolution Lidar (HSRL)1,2 interferometrically separates particulate from molecular backscatter. By using the distribution of molecular scattering as a known target, the HSRL achieves unambiguous, calibrated measurements of atmospheric extinction, backscatter cross section, and backscatter phase function.