Effect of laser beam on depolarization characteristics of backscattered light in discrete random media

When lidar is used to detect the microphysical properties of clouds and aerosols, it is a spot when the laser reaches the clouds. This is because the lidar has a certain divergence angle, and the location of the lidar is at a certain distance from the clouds. In this paper, a Monte Carlo method for simulating multiple scattering in clouds by lidar is presented, and the influence of the size and shape of the spot on the backscattering of polarized light in clouds is analyzed. From the calculation results, it can be seen that the spot will increase the depolarization ratio of lidar, and the larger of the size of the spot, the larger the depolarization ratio. In addition, depolarization ratio increases with the increase of optical thickness and field of view angle. The methods and conclusions in this paper are of great significance for long-distance detection of discrete random media by laser.