【作者】 许小永；

【导师】 王振会；

【作者基本信息】 南京气象学院 ， 大气物理学与大气环境， 2002， 硕士

【摘要】 本文主要分两部分，第一部分，根据后向散射截面测量实验所选用的扁椭球形和球锥扁椭球形粒子，运用DDA法和T-矩阵法计算了它们对偏振电磁波的后向散射截面。经对比显示，DDA法计算结果、T-矩阵法计算结果和实验测量资料三者之间一致性较好。计算结果和实验结果表明，对3.2cm、5.6cm和10.7cm波，非球形雨滴和冰粒后向散射截面随尺寸变化具有相同的特点，即开始随粒子的增大而增大，然后进入谐振区。球锥扁椭球形冰粒的差反射率因子与粒子形状参数水平-垂直尺度比呈很好的线性正相关。第二部分，利用T-矩阵法计算了雨区和雹区的雷达反射率因子Z_HH、差反射率因子Z_DR和线退偏振因子L_DR，其中涉及到降水区粒子的不同取向、不同形状、不同相态。结果表明：降水强度越大，雨区和雹区的Z_HH越大；雹区的Z_DR有时为负值；降水粒子取向对L_DR影响很大。文中还对包含多个球形粒子的粒子群散射作了初步计算研究。更多还原

【Abstract】 In the first, the backscattering cross-sections of liquid and ice oblates and sphere-cone-oblate ice particles simulated for lab observations, are calculated by the discrete-dipole approximation (DDA) and the T-matrix method. The 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. Theoretical and experimental analyses indicate that the backscattering ability of nonspherical raindrops and ice particles presents a curved change as the particle size 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 but also their shapes. There is a linear relationship between differential reflectivity ZDR and the shape factor defined as the ratio of the horizontal scale to the vertical scale of a particle. Secondly, This paper theoretically examines the properties of reflectivity ZHH, differential reflectivity ZDR and the linear depolarization factor LDR of rain and hail at 3.2cm, 5.6cm and 10.7cm wavelengths. The computation has been performed for the precipitation particles having different shapes, orientations, densities, water contents, and water coatings. The results should prove useful for interpreting radar measurements. Moreover, the scattering features of the cluster consisting of several non-overlapping, external spheres are briefly discussed.更多还原