Simulation of radiation transfer properties of polarized light in non-spherical aerosol using Monte Carlo method

Abstract

The shape of atmospheric aerosol is an important factor that influences radiation transfer. In this paper, a vector radiation transfer model based on Monte Carlo method is systematically introduced, and its accuracy is validated against the published results. and the sensitivity of Stokes vectors of transmitted and reflected light to aerosol shape is discussed when polarized light incidents. In addition, the influence of the particle shape on the depolarization ratio, transmission rate and the reflection rate is analyzed for incident light with different polarization states. Simulation results show that for the incident light in different polarization states, the sensitivity of the Stokes vectors of the diffuse light to different aerosol shapes is not the same in different viewing directions, and the Q, U, V elements of Stokes vector are all insensitive to the change of particle shape near the direction of the zenith angle 0°. It is evident that the aerosol shapes have a stronger influence on the depolarization ratio for reflected diffuse light compared with that for transmitted diffuse light, and there are also remarkable differences between the degree of depolarization of the diffuse light when the polarization states of the incident light are different. Results also show that the aerosol shape has a significant influence on the whole transmission rate and the reflection rate, and with the increasing of propagation distance, the influence also becomes more remarkable. Compared with particle shape, the influence of polarization states of incident light is relatively small, the transmission rate of horizontally-polarized light is slightly larger than that of unpolarized light, while for perpendicularly-polarized light, its results is opposite. For circularly polarized light, the results is almost the same as that of unpolarized light.