Scattering near specular direction for horizontally oriented ice discs

Scattering phase function on horizontally oriented ice particles near the specular reflective direction is analytically modeled using a mixed method combining direct reflection and Fraunhofer diffraction components, where particles are simply treated as circular facets and the effect of fluttering is introduced under the assumption of Gauss distribution. The obtained model expression reveals that the essence of far-field scattering around specular direction is the diffraction pattern modulated by fluttered geometric reflection. Four groups of experiments are designed to validate this model at different wavelengths and incidence angles, and the calculated phase functions present good agreement both in distributions and peak values with that of T-matrix method in conjunction with a Monte Carlo stochastic process.