Scattering properties of non-spherical particles in the CO2 shortwave infrared band

Abstract

Based on the T-matrix method and the generalized multiparticle Mie-solution (GMM) method combined with diffusion-limited aggregation simulator, the scattering properties of non-spherical particles and aggregates are simulated at 1.6 μm and 2.0 μm. And the effects of the equal-volume sphere radius, the complex refractive index, the particle shape and the relative humidity (RH) on the scattering characteristics parameters of non-spherical aerosol are analyzed. The results show that besides the equal-volume sphere radius and the particle shape, the RH could also lead to a large change of the scattering properties. And the relative differences in back scattering between spherical particles and non-spherical particles in different relative humidities are all larger than 18%. If the RH increases, the back scattering will increase for small-size particles, while the back scattering of large-size ones will decrease. The asymmetry factors of the smaller aggregates are 0.023 averagely greater than those of the single equal-volume non-spherical particles, which the asymmetry factors of the bigger aggregates are 0.055 averagely less than those of the single equal-volume non-spherical particles. The differences in single scattering albedo between the two wavelengths 1.6 μm and 2.0 μm are all much larger for either aggregates or single equal-volume particles, and the biggest difference reaches 0.226. This research has scientific significance for studying the aerosol multiple scattering influencing on the accuracy of CO2 satellite retrieval.