球锥扁椭球冰粒后向散射实验与DDA计算研究

Lab Observation and DDA Computation on the Backscattering Features of Sphere-Cone-Oblate Ice Particles

采用实验室观测和 DDA法理论计算 ,分别获得了球锥扁椭球形冰粒对 3 .2、5.6和 1 0 .7cm三种波长极化波的后向散射特性数据。结果表明 ,测量资料和计算数据具有很好的一致性。球锥扁椭球形冰粒的后向散射截面大小不仅依赖于其尺寸 (等容半径 )而且受其形状影响 ,“差反射率因子 ZDR”与粒子形状参数“水平—垂直尺度比”呈很好的线性正相关。

The measuring experiment and DDA calculations for the scattering of ice particles are briefly presented in this paper. Twenty sphere-cone-oblate ice particles are simulated for lab observations and DDA calculations.Theoretical results are compared with the experiment data obtained with a microwave measuring system.It is shown that the theoretical results are consistent with the experiment data in general.As a result,the reliability of theoretical model is proved.Theoretical and experimental analyses indicate that the backscattering ability of sphere-cone-oblate ice particles increases as the particle size parameter increases,and fluctuates in the so-called resonance region.The backscattering cross-sections of sphere-cone-oblate ice particles depend upon not only their sizes(equivolume spherical radii R e)but also their shapes.There is a linear relationship between differential reflectivity Z DR and the shape factor which is defined as the ratio of the horizontal scale to the vertical scale of a particle.