研究目的
To observe and study the effects of the volume packing density on polarimetric scattering by deposited particulate materials, comparing the vector radiative transport equation (VRTE) and the plane wave plane parallel (PWPP) models for polarized bidirectional reflectance and transmittance.
研究成果
The PWPP model results converge to VRTE predictions at low volume fractions (～5% or less) but diverge at higher fractions, depending on particle size and refractive index. Increasing volume fraction shifts scattering towards backward directions. The PWPP model captures coherent backscattering effects (brightness and polarization opposition) not predicted by VRTE, with dependencies on volume fraction and particle size. Further refinement is needed for better angular resolution and computational efficiency.
研究不足
The PWPP model requires significant computational resources and time, especially for averaging over many configurations. The model assumes perfectly flat boundaries and periodic conditions, which may not represent natural deposits accurately. Normal incidence complicates the identification of coherent backscattering effects due to specular reflection interference. The angular resolution is limited by the unit cell width, affecting the precision of opposition effect measurements.
1：Experimental Design and Method Selection:
The study compares the PWPP model (an exact method based on solving Maxwell's wave equations for a periodic lattice) and the VRTE (a phenomenological method solved using the adding-doubling method). The PWPP model involves generating random configurations of spherical particles in a unit cell and averaging results over multiple configurations to obtain random media properties.
2：Sample Selection and Data Sources:
Simulations are performed on monodisperse spherical particles representing ice (refractive index m=1.31) and mineral matter (m=1.5+0.01i), with size parameters of 1 and 2, and volume fractions ranging from approximately 0.05 to 0.
3：31) and mineral matter (m=5+01i), with size parameters of 1 and 2, and volume fractions ranging from approximately 05 to List of Experimental Equipment and Materials:
3.
3. List of Experimental Equipment and Materials: Computational models and codes are used; no physical equipment is mentioned. The PWPP code is developed in Fortran-90+MPI, and the VRTE code is written in MATLAB, run on a workstation computer and a compute cluster.
4：Experimental Procedures and Operational Workflow:
For PWPP, random particle configurations are generated using Monte Carlo methods in a unit cell, and the system of equations is solved iteratively. For VRTE, the adding-doubling method is applied with numerical integration. Both methods calculate bidirectional reflectance and transmittance for normal incidence.
5：Data Analysis Methods:
Results are averaged over 500 to 1000 configurations for PWPP to reduce speckle. Comparisons are made between PWPP and VRTE predictions, focusing on scattering matrix elements and opposition effects.
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