Transient polarized radiative transfer in cloud layers: numerical simulation of imaging lidar returns.

In this paper, we investigate the time-dependent backscattering halo of a pulsed light beam in a layer of scattering medium. We start from numerical simulations of polarized radiative transfer in the layer, which immediately reveals the effect under investigation. Then we analyze time-dependent structure of the light field using the simulation results. From the radiation field, we extract two principal components, immediately forming the halo structure. For each diffuse and ballistic component, we use the proper theoretical model, yielding a convenient analytic description of the time-dependent behavior of the radiation field. From the theory developed by us, we derive a simple numerical criterion of visibility of the halo. Finally, we validate our theory against Monte Carlo radiative transfer simulations. Thus, we propose a quantitative explanation of the studied effect.