Analyzing and modeling the SMOS spatial variations in the East Antarctic Plateau
Analyzing and modeling the SMOS spatial variations in the East Antarctic Plateau
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东南极高原SMOS空间变化分析与建模
DOI：
10.1016/j.rse.2016.02.037
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发表时间：
2016
影响因子：
13.5
通讯作者：
G. Picard
中科院分区：
文献类型：
--
作者：
G. Macelloni;M. Leduc;M. Brogioni;C. Ritz;G. Picard
在南极东部高原采集的SMOS亮温（TB）揭示了在只有高频被动微波观测时从未观测到的l波段空间特征，这开辟了一个新的研究领域。由于穿透深度要大得多，对微波冰盖发射的建模不仅需要考虑地表的雪况，还应包括冰川学信息。即使由于冰介电常数虚部的不确定性，l波段的穿透深度不为人所知，也很可能在几百米数量级，这意味着近1000米深度上的冰的温度会影响发射。在这样的深度上，温度与地表条件和冰盖厚度有关，而冰盖厚度又取决于基岩地形和其他冰川学变量。本文旨在对观测到的垂直极化下接近布鲁斯特角的tbspace变化提供一个全面的理论解释，以限制表面和垂直密度变化对公司的影响。为了给用于模拟TBdata的微波发射模式提供可靠的输入，利用冰川学模式对温度廓线进行了深入分析。对东南极洲总计2000公里的三个样带的模拟数据和观测数据的比较指出，虽然排放模式能够解释几个开尔文（0.7和2.9 K）的温度空间变化，但它们无法正确预测其绝对值。研究还表明，模拟低频微波数据的主要限制因素是目前可用的冰介电常数虚部的不确定性。
The SMOS brightness temperature (TB) collected on the East Antarctic Plateau revealed spatial signatures at L-band that have never before been observed when only higher-frequency passive microwave observations were available, and this has opened up a new field of research. Because of the much greater penetration depth, modeling the microwave ice sheet emission requires taking into account not only snow conditions on the surface, but should also include glaciological information. Even if the penetration depth of the L-band is not well known due to the uncertainty on the imaginary part of the ice permittivity, it is likely to be of the order of several hundreds of meters, which means that the temperature of the ice over a depth of nearly 1000 m influences the emission. Over such a depth, the temperature is related to both the surface conditions and to the ice sheet thickness, which in turn depends on the bedrock topography and on other glaciological variables. The present paper aims to provide a thorough theoretical explanation of the observed TBspatial variation close to the Brewster angle at vertical polarization, in order to limit the effect of surface and vertical density variability in the firn. In order to provide reliable inputs to the microwave emission models used for simulating TBdata, an in-depth analysis of the temperature profiles was performed by means of glaciological models. The comparison between simulated and observed data over three transects totalling 2000 km in East Antarctica pointed out that, whereas the emission models are capable of explaining the TBspatial variations of several kelvins (0.7 and 2.9 K), they are unable to predict its absolute value correctly. This study also shows that the main limiting factor in simulating low-frequency microwave data is the uncertainty in the currently available imaginary part of the ice permittivity.