Polarization performance of a polydisperse aerosol atmosphere based on vector radiative transfer model

Abstract

The effect of aerosol particles in the atmospheric radiative transfer has great uncertainty. A computer code for accurate calculation of the optical properties and vector radiative transfer of polydisperse aerosol system has been written in C++ language. In this paper, the polydisperse aerosol system has been divided into multiple size regions according to the particle size, and the optical properties of each region have been calculated separately and applied in the radiative transfer calculation. The results show that this method is significantly different from the method that is not divided into regions, with an average error of about 5.77%. The radiance mode and polarization mode in different solar zenith angle (SZA, from 30° to 70°), aerosol optical depth (AOD, from 0.2 to 1.0), and three aerosol types have been also calculated. The results also show that the radiative transfer is highly sensitive to all parameters. The polarization distribution but not the degree of polarization (DOP) is affected by SZA. The depolarization effects of aerosol are affected by AOD and particle size distribution. The maximum DOP decreased by 0.2 and 0.3 with the increasing AOD and average particle size, respectively. The distribution of Stokes parameters and atmospheric absorption is mainly affected by the complex refractive index. The Stokes component distribution of water-soluble aerosol is different from dust and soot, and the atmospheric transmissivity from dust to soot decreases about 26%. In addition, the scattering angles of the maximum DOP of the three aerosol types are all greater than 90°, which reflects the important effect of the element P12 on the polarization mode. This research has guiding significance for many fields such as energy utilization, climate prediction, atmospheric remote sensing, and so on.