Search for proxy indicators of young sea ice thickness
Search for proxy indicators of young sea ice thickness
复制标题
寻找年轻海冰厚度的代理指标
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
P. Kanagaratnam
中科院分区：
文献类型：
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作者：
I. Zabel;K. Jezek;S. Gogineni;P. Kanagaratnam
对于那些对海洋与大气的相互作用、海洋的热和化学状态以及海冰动力学感兴趣的人来说，从太空确定年轻海冰的厚度仍然是一个难以实现的目标。最近的实验和模型显示了新冰的主动和被动微波特征与冰厚度之间的关系。决定微波特征的两个主要过程是介电特性的变化和表面粗糙度的变化。在本文中，我们研究了这两个过程在确定雷达后向散射方面的竞争，表面粗糙度作为新冰厚度指标的有效性，以及观测与冰厚度相关的散射变化的最佳传感器参数。我们提出了基于实验室生长的盐冰的雷达观测的模拟。这些观测结果证实，在13.9 GHz雷达背向散射中，表面散射比体积散射占优势，这些背向散射来自年轻的、粗糙的冰，在大多数角度下，对于年轻的、30°以下的光滑冰。虽然在安静条件下，rms粗糙度和后向散射（5.3 GHz和13.9 GHz， 23°入射和VV偏振）在冰增长约10厘米后一起增加，但在真实海冰中，表面粗糙度和冰厚不太可能简单地联系在一起，因为表面粗糙度会由于风、波和雪的作用而迅速变化。然而，模拟表明，霜花的形成可以被星载雷达探测到，并且可以用来对大约5-20厘米厚的冰进行分类，因为这是一个独特的、短暂的事件，发生在限制冰厚度的物理条件下。我们的实验数据表明，未来的传感器工作在近12°入射角附近，可能为探测近表面介电特性和冰厚之间的关系提供潜力，因为粗糙度和降雪变化的影响在这个角度附近最小。
The determination of young sea ice thickness from space remains an elusive goal for those interested in the interaction of the oceans and the atmosphere, the thermal and chemical state of the ocean, and sea ice dynamics. Recent experiments and models have shown relationships between active and passive microwave signatures of new, growing ice and ice thickness. The two processes that dominate in determining the microwave signature are changes in dielectric properties and changes in surface roughness. In this paper we investigate the competition between these two processes in determining radar backscatter, the usefulness of surface roughness as an indicator of young ice thickness, and the optimum sensor parameters for observing changes in scattering linked to ice thickness. We present simulations that are based on radar observations made on laboratory-grown saline ice. These observations confirm that surface scattering dominates over volume scattering for 13.9 GHz radar backscatter from young, rough ice at most angles and for young, smooth ice below 30°. Although rms roughness and backscatter (at 5.3 and 13.9 GHz, 23° incidence, and VV polarization) increase together after about 10 cm of ice growth under quiet conditions, it is unlikely that surface roughness and ice thickness are simply connected in real sea ice, where surface roughness can change rapidly due to the action of wind, waves, and snow. Simulations show, however, that formation of frost flowers is detectable by spaceborne radar and can serve to classify ice of roughly 5–20 cm thickness since it is a distinct, transient event that occurs under physical conditions that constrain the thickness of the ice. Our experimental data show that future sensors operating near 12° incidence may offer potential for probing the relationship between near-surface dielectric properties and ice thickness, since the effects of variability in roughness and snowfall are minimized near this angle.