Investigating the radiative properties of large dust aggregate particles via the Monte Carlo ray tracing method

Understanding the radiative properties of particles is essential for interpreting and analyzing atmospheric remote sensing, target detection, combustion diagnostics, etc. At present, there is a relative lack of studies and understanding of the radiative properties of large aggregate particles. In this work, we comprehensively investigate the radiative properties of large dust aggregate particles via the developed Monte Carlo ray tracing method. Large dust aggregate models with monodisperse and polydisperse monomers are constructed, respectively. The effects of various factors on the radiative properties of large dust aggregate particles are analyzed. We find that the larger geometric standard deviation and the greater number of monomers lead to slightly larger backscattering and an increase of the overall radiative energy distribution on the receiving surface. With increasing the size parameter, the scattering phase function becomes smoother and the difference between the scattering phase function of spheres and aggregates diminishes. The absorptivity is proportional to the size parameter and inversely proportional to the number of monomers. At a size parameter of 100, the absorptivity and the peak of the radiative energy distribution of monodisperse monomer aggregates are higher than those of polydisperse monomer aggregates, and gradually converge with the increase of particle size parameter. Overall, this work helps to enhance the knowledge of the radiative properties of large aggregate particles.