Modeling of Microwave Scattering From Cloud Ice Crystal Aggregates and Melting Aggregates: A New Approach
Modeling of Microwave Scattering From Cloud Ice Crystal Aggregates and Melting Aggregates: A New Approach
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云冰晶聚集体和熔融聚集体的微波散射建模：一种新方法
DOI：
10.1109/lgrs.2010.2041633
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发表时间：
2010
影响因子：
4.8
通讯作者：
J. Verlinde
中科院分区：
文献类型：
--
作者：
G. Botta;K. Aydin;J. Verlinde
用一种新的方法模拟了冰晶聚集体及其熔化过程的微波散射特性，并与用有效介电常数表示法得到的结果进行了比较。聚集体是由任意长度的柱状晶体(宽度是长度的函数)组成的，柱状晶体由一串直径等于柱状物宽度的相互接触的冰球组成。熔化聚集体使用的模型结合了实验观察到的熔化过程特征的主要方面。用广义多粒子Mie方法计算了干态和熔化集合体的散射截面。T-矩阵方法用于计算具有有效介电常数模型和扁球形状的每个聚集体的整体表示。3 GHz和35.6 GHz的后向散射截面显示出两种方法对于干态聚集体和融化聚集体的显著差异。对于大于3毫米的尺寸，这些差异的范围从3 GHz的几个分贝到35.6 GHz的远高于7分贝。在熔化过程中，消光截面也观察到明显的差异。结果表明，干冰晶体聚集体和融化冰晶聚集体的有效介电常数模型不能很好地反映聚集体组成晶体(和融化过程中的水滴)之间的相互作用。因此，必须谨慎使用整体模型，特别是在毫米波长。
Ice crystal aggregates and their melting process are modeled with a new approach for determining their microwave scattering characteristics and are compared with those obtained using effective dielectric constant representations. The aggregates are constructed from columnar crystals of random lengths (with the width being a function of the length), which are composed of a string of touching ice spheres with diameters equal to the column's width. The aggregates are melted using a model that incorporates the primary aspects of experimentally observed features of the melting process. The generalized multiparticle Mie method is used for computing the scattering cross sections of the dry and melting aggregates. The T-matrix method is used for computations involving a bulk representation of each aggregate with an effective dielectric constant model and an oblate spheroidal shape. The 3- and 35.6-GHz backscattering cross sections show significant differences between the two methods for both dry and melting aggregates. For sizes larger than 3 mm, these differences range from several decibels at 3 GHz to well over 7 dB at 35.6 GHz. Significant differences are also observed in the extinction cross sections during the melting process. It is concluded that the effective dielectric constant models of dry and melting ice crystal aggregates do not represent the interactions between the constituent crystals (and water droplets during melting) of the aggregates very well. Hence, bulk models must be used with caution particularly at millimeter wavelengths.