Geometrical-optics code for computing the optical properties of large dielectric spheres

Area of Science:

• Physics, Optics, and Atmospheric Science

Background:

• Absorption of near-infrared radiation by snow grains significantly impacts snow's radiative properties.
• Accurate computation of scattering and absorption cross sections for dielectric spheres is essential for radiative transfer models.

Purpose of the Study:

• To develop a novel geometrical-optics code (GOMsphere) for calculating scattering and absorption properties of large dielectric particles.
• To validate the GOMsphere code against established Mie scattering and Monte Carlo codes.

Main Methods:

• Development of a geometrical-optics code (GOMsphere) for dielectric spheres with arbitrary complex refractive indices.
• Truncation of internal reflections/transmissions based on incident irradiance ratios and angle of incidence.
• Hybrid algorithm using bisection and Newton-Raphson methods for calculating phase functions.

Main Results:

• GOMsphere accurately computes scattering and absorption cross sections for large dielectric spheres across various wavelengths (UV to microwave).
• The code effectively calculates phase functions for both near- and far-field scattering.
• Validation against Mie scattering (MIE0) and Monte Carlo codes confirms GOMsphere's reliability.

Conclusions:

• GOMsphere provides a robust method for characterizing the optical properties of large dielectric spheres, including snow melt clusters.
• The code can be integrated with Mie scattering calculations for comprehensive single-scattering property determination.
• This advancement aids in more accurate modeling of radiative transfer in snowpack and other relevant media.