Effects of temperature and orientation on 3.2mm radar backscattering from ice crystals

Millimeter wave radar signals depending on backscattering characteristics of particles and particles size distribution can be used to inverse the microphysical parameters of clouds, but ice clouds are composed of non-spherical ice crystals, so various factors of impacting on the scattering from non-spherical particles must be considered. However, there are few papers that account for the influence of temperature and orientation on the backscattering characteristics of hexagonal ice crystals with 3.2mm radar in detail. The effects are investigated by modeling the discrete dipole approximation (DDA) method in this paper. At vertical radar wave, the value of backscattering cross sections of hexagonal ice crystals with horizontal orientation (2D) is twofold more than random orientation (3D). With the antenna elevation angle increases, there is a large increase of radar cross sections for hexagonal columns, but a slight change for hexagonal plates with 2D. The contributions from orientations must be considered in calculating scattering characteristics of non-spherical ice crystals. Backscattering cross sections change slightly about 2.75% when the temperature changes from 0° to 173°. It should also be noted that aspect ratio has a large impact on radar cross sections. Such calculations can extend scattering characteristics database of ice particles. In this paper, we provide some ideas for exploring the scattering from ice crystal and theoretical basis for using the 3.2mm radar echo to inverse the characteristics of clouds.