Solution of the light scattering problem by small atmospheric ice crystals by discrete dipole approximation and comparison with the physical optics approximation

The paper presents a solution to the problem of light scattering by small randomly oriented hexagonal ice crystals of cirrus clouds. The solution was obtained both within the discrete dipole approximation and within the physical optics approximation. The particle sizes ranged from 0.2 to 6 μm. The wavelength of the incident radiation is 0.532 μm, the refractive index is 1.3116. The results of the comparison of the solutions obtained within the framework of the discrete dipole approximation with the physical optics approximation are shown. It is found that the solutions are in good agreement, however, to solve the problem of light scattering in the vicinity of the backward direction, which is important for the interpretation of lidar data, it is necessary to continue the calculations by the discrete dipole approximation up to particle sizes of about 10 μm.