SCATTERING OF SOLAR-RADIATION BY HEXAGONAL ICE CRYSTALS

The classical ray optics approximation has been applied to compute the angular scattering of light by finite-sized hexagonal ice crystals in the form of columns and plates. The results are presented at a wavelength of 0.55 μm for a random orientation of the crystals either in space or in a plane. The results are also compared to those of ice spheres. For the first time the angular light scattering of platelike crystals and a quantitative description of the 46° halo are given. Contrary to earlier studies, it is shown that both plate- and columnlike ice crystals show a strong backscattering. In agreement with previous studies, ice spheres are found to scatter-when compared to ice prisms-less energy at angles near 90°. With regard to the effect of orientation on the light scattering, it is shown that columnlike crystals randomly oriented in a plane behave rather like spherical particles and not like columns randomly oriented in space. © 1979 Optical Society of America.