Radio-wave depolarization and scattering within ice sheets: a matrix-based model to link radar and ice-core measurements and its application
Radio-wave depolarization and scattering within ice sheets: a matrix-based model to link radar and ice-core measurements and its application
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DOI：
10.3189/172756506781828548
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发表时间：
2006-01-01
影响因子：
3.4
通讯作者：
Matsuoka, Kenichi
中科院分区：
文献类型：
--
作者：
Fujita, Shuji;Maeno, Hideo;Matsuoka, Kenichi
晶体取向结构（COF）对冰盖流动有较大的影响。早期的雷达研究表明，基于cof的双折射发生在冰盖内。极地冰中的无线电波散射是由于介电常数和电导率的物理性质变化造成的，而介电常数和电导率的物理性质变化是由密度、酸度和COF的不同值引起的。我们提出了一个改进的数学模型，可以同时处理所有这些现象。我们使用这个基于矩阵的模型来研究在各向同性和各向异性边界上散射的去极化无线电波的双向传播。在数值模拟的基础上，从雷达极化和频率两个方面论证了COF对雷达信号的影响。然后，我们将模拟特征与在东南极洲两个对比内陆站点获得的VHF雷达数据进行比较，在那里，COF从冰芯研究中已知。这两个地点分别是位于圆顶山顶附近的圆顶富士和位于汇合冰流区域的瑞穗。圆顶富士的数据主要是由双折射引起的典型特征。双折射散射和各向异性散射对瑞穗雷达数据均有影响。我们认为雷达方法可用于确定冰盖双折射的主轴和强度。
Crystal-orientation fabric (COF) has a large influence on ice-sheet flow. Earlier radar studies have shown that COF-based birefringence occurs within ice sheets. Radio-wave scattering in polar ice results from changing physical properties of permittivity and conductivity that arise from differing values of density, acidity and COF. We present an improved mathematical model that can handle all these phenomena together. We use this matrix-based model to study the two-way propagation of depolarized radio waves that scatter at both isotropic and anisotropic boundaries. Based on numerical simulations, we demonstrate how COF affects the radar signals in terms of radar polarization and frequency. We then compare the simulated features with VHF radar data obtained at two contrasting inland sites in East Antarctica, where COF is known from ice-core studies. These two sites are Dome Fuji, located near a dome summit, and Mizuho, located in a converging ice-flow region. Data at Dome Fuji are dominated by typical features resulting from birefringence. In contrast, both birefringence and anisotropic scattering affect the radar data at Mizuho. We argue that radar methods can be used to determine principal axes and strength of birefringence in the ice sheets.