Theoretical Study on Single-Scattering Properties of Ice Particles of Different Orientation at 94 GHz
The single-scattering properties of hexagonal columns and plates were studied using Discrete Dipole Approximation at 94GHz, including scattering efficiency, absorption efficiency, asymmetry factor, backscattering cross section and phase function. Random and horizontal orientations of particles were compared, and 35 sizes of maximum dimension D ranging from 1 um to 10 mm were selected. The results indicate that scattering and absorption efficiencies of horizontally oriented hexagonal columns are larger than those of the randomly oriented ones, whereas this phenomenon does not appear to hexagonal plates. The asymmetry factor of horizontally oriented hexagonal plates has a negative value, which means that the backscattered energy is more than forward energy when the particle is large enough. The backscattering cross sections of horizontally oriented hexagonal columns and plates are larger than those of random orientation, which can be explained by that different cross sections of particles will be exposed to incident plane wave. When the particle size is smaller than incident wavelength, little scattering energy difference between random and horizontal orientation exists, while if the particle is larger than incident wavelength, a turning point will happen at θ=110˚, which can be explained by the theory of energy conservation.