Multiple-scattering effect on ozone retrieval from space-based differential absorption lidar measurements

Influence of atmospheric and system parameters on multiple scattering in spaceborne backscatter lidar measurements

We have simulated backscatter signals of spaceborne lidar systems with the help of a Monte Carlo model. Calculations were performed for various combinations of system parameters. As typical examples of atmospheric observation targets, two kinds of cirrus cloud and two kinds of aerosol were considered. Both total multiple scattering and the significance of individual higher scattering orders are discussed. For all cases, an approximate multiple scattering factor F was calculated that can be used to correct the single-scattering lidar equation to account also for multiple scattering.

Effect of multiple scattering on depolarization measurements with spaceborne lidars

An analytical model based on the integration of the scattering-angle and light-path manifold has been developed to quantify the effect of multiple scattering on cirrus measurements obtained with elastic polarization lidars from space. Light scattering by molecules and by a horizontally homogeneous cloud is taken into account. Lidar parameter, including laser beam divergence, can be freely chosen. Up to 3 orders of scattering are calculated. Furthermore, an inversion technique for the retrieval of cloud extinction profiles from measurements with elastic-backscatter lidars is proposed that explicitly takes multiple scattering into account. It is found that for typical lidar system parameters such as those of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instrument multiple scattering does not significantly affect depolarization-ratio measurements in cirrus clouds with small to moderate optical depths. For all simulated clouds, the absolute value of the difference between measured and single-scattering volume depolarization ratio is < 0.006. The particle depolarization ratio can be calculated from the measured volume depolarization ratio and the retrieved backscatter ratio without degradation of accuracy; thus characterization of the various cirrus categories in terms of the particle depolarization ratio and retrieval of cloud microphysical properties is feasible from space. The results of this study apply to polar stratospheric clouds as well.