Backscattering properties of randomly oriented hexagonal hollow columns for lidar application.

The study of the optical properties of cirrus clouds is necessary to improve the accuracy of interpreting data from space lidars and ground-based lidar networks. Existing databases of backscattering properties do not include data on hollow columns. In this paper, the backscattering properties of randomly oriented hollow column ice crystal particles in cirrus at wavelengths of 355 nm, 532 nm, and 1064 nm have been investigated.

Lidar backscatter simulation for angular scanning of cirrus clouds with quasi-horizontally oriented ice crystals.

Backscattering properties of ice crystals are numerically investigated in the case of plate-like quasi-horizontally oriented crystals of cirrus clouds. In this case, a vertically oriented lidar detects the specular reflection from the clouds while a lidar with angular scanning allows one to infer the microphysical properties like the transverse shape of the crystals. It is shown that the depolarization ratio as a function of the lidar tilt reveals a step at a lidar tilt of about 30° from the vertical.

Radar-lidar ratio for ice crystals of cirrus clouds.

Simultaneous measurement of lidar and radar signals returned from the same cirrus clouds is a prospective method for retrieving the cloud microphysics, i.e. size and shape of the ice crystals constituting the clouds.

Coherent and incoherent backscattering by a single large particle of irregular shape.

Intensity of light scattered by a large randomly oriented particle of irregular faceted shape at the backscattering cone of [170°, 180°] is calculated using the physical-optics approximation. It is shown that the backscattered light for a single large particle of irregular shape is split into the coherent and incoherent parts similarly to the phenomena well-known for multiple scattering media. For the model of irregular faceted particles assumed in the paper, the coherent part creates the coherent backscattering peak whose angular width is equal approximately to the ratio of wavelength/(particle size).