Backscattering Characteristics of Optical and Electromagnetic Waves in Joint Sensing of Cirrus Clouds by a Polarizing Lidar (0.355 µm) and a 94-GHz Radar

In this work, the problem of radiation scattering by ice crystals typical for cirrus clouds is solved for a 94-GHz radar (wavelength 3189 µm) and a lidar (wavelength 0.355 µm); the ice refractive indices are 1.7864 + 0.0032 i and 1.3249 + 0 i , respectively. The scattering matrices are calculated within the physical optics approximation and the discrete dipole approximation for the case of randomly oriented particles with sizes from 4 to 1000 µm. The ratio of the radar and lidar backscattering signals in the backward direction (the so-called radar–lidar ratio) is calculated for a wide range of the particle size for typical shapes of cirrus cloud ice crystals. It is shown that this ratio can be used for estimating the size of ice crystals in cirrus clouds.