Enhanced lidar backscattering by quasi-horizontally oriented ice crystal plates in cirrus clouds Conference Paper uri icon


  • The backscattering of light by quasi-horizontally oriented hexagonal ice plates is investigated because of its pertinence to lidar measurements of cirrus clouds. For oriented ice crystals, the commonly used geometric optics ray-tracing method is not applicable to the computation of the scattered field in certain scattering directions, in particular, the backscattering direction, because of the singularity problem inherent to the ray-tracing technique. In this study, we solve for the electric field due to scattering by quasi-horizontally oriented ice plates using an approach based on the electromagnetic wave theory. We simplify the analysis by ignoring the effect of the plate's side faces on the internal field inside the particle. This is a reasonable approximation when the ratio of the particle diameter to its thickness is large. This approximation is also valid if the tilt of the particle's symmetric axis from zenith is small and the size parameter is large. The present numerical results indicate that very strong oscillations in the backscattering cross section occur with the variation of size parameter. Furthermore, the bulk backscattering intensity has been calculated by including the effect of a particle size distribution and the random tilt of particle symmetric axis within a small angular region, for example, 2. A strong dependence is found between the lidar backscattering cross section and the degree of the random tilt of the particles. A combination of the present method with the T-matrix method, which works well for particles having small and moderate size parameters, may provide a more complete picture of the lidar backscattering by quasi-horizontally oriented ice plates. 2003 Elsevier Science Ltd. All rights reserved.

published proceedings

  • Journal of Quantitative Spectroscopy and Radiative Transfer

author list (cited authors)

  • Yang, P., Hu, Y. X., Winker, D. M., Zhao, J., Hostetler, C. A., Poole, L., ... Reichardt, J

publication date

  • January 1, 2003 11:11 AM