Characterizing C-band backscattering from thermokarst lake ice on the Qinghai–Tibet Plateau
Characterizing C-band backscattering from thermokarst lake ice on the Qinghai–Tibet Plateau
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DOI：
10.1016/j.isprsjprs.2015.02.014
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发表时间：
2015-06
影响因子：
12.7
通讯作者：
B. Tian;Zhen Li;M. Engram;F. Niu;P. Tang;Pengfei Zou;Juan Xu
中科院分区：
文献类型：
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作者：
B. Tian;Zhen Li;M. Engram;F. Niu;P. Tang;Pengfei Zou;Juan Xu
本研究在气象观测和湖冰实地测量的基础上，研究了2003-2010年青藏高原热岩溶湖泊和高寒草甸的多时相C波段VV偏振雷达后向散射值。为了了解湖冰的散射机制，开发了湖冰的散射模型，该模型更新了先前开发的模型中采用的一些假设，包括冰水界面的粗糙度和湖冰中垂直堆叠的厘米级气泡的形状。我们得出以下结论：首先，在24°附近的入射角范围内，C波段VV偏振ENVISAT-ASAR数据的后向散射强度表现出很强的时间依赖性，这与QTP上的冰生长和腐烂过程有关。与高纬度地区相比，本文还讨论并记录了该高海拔地区湖冰的一些独特的后向散射特征。其次，通过使用周围高寒草甸反向散射强度的阈值 -12 dB，可以在雷达图像中识别该地区秋季湖泊结冰和春季结冰的时间。最后，应用散射模型的结果表明，冰水界面的表面散射和湖冰中嵌入的气泡的体积散射是C波段VV偏振SAR的主要散射机制，冰水界面的粗糙度和气泡尺寸是最敏感的因素。
On the basis of weather observations and field measurements of lake ice, this study investigates multi-temporal C-band VV-polarized radar backscattering values from the thermokarst lakes and alpine meadow on the QTP during the period 2003–2010. In order to understand the scattering mechanism of lake ice, a scattering model is developed for lake ice that updates some assumptions adopted in previously developed models, including the roughness of the ice–water interface and the shape of vertically stacked centimeter-sized bubbles in the lake ice. We conclude the following: First, with a incidence angle range near 24°, the backscattering intensities of C-band VV-polarized ENVISAT–ASAR data exhibit a strong dependence on time, which is related to the processes of ice growth and decay on the QTP. Some unique backscattering characteristics of lake ice in this high-altitude region, as compared to those for high-latitude regions, are also discussed and documented in the paper. Secondly, the timing of lake ice-on in fall and ice-off in spring for this region can be identified in radar images by using a threshold of −12 dB for the backscatter intensity of the surrounding alpine meadow. Finally, the results of applying the scattering model indicate that surface scattering from the ice–water interface and volume scattering from gas bubbles embedded in the lake ice are the dominant scattering mechanisms for C-band VV polarized SAR and that the roughness of the ice–water interface and also bubble size are the most sensitive factors.