Numerical Studies of Sea Surface Scattering With the GMRES-RP Method
Numerical Studies of Sea Surface Scattering With the GMRES-RP Method
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DOI：
10.1109/tgrs.2013.2257800
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发表时间：
2014-04
影响因子：
8.2
通讯作者：
Hejia Luo;Guangdi Yang;Yinhui Wang;Jiancheng Shi;Yang Du
中科院分区：
文献类型：
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作者：
Hejia Luo;Guangdi Yang;Yinhui Wang;Jiancheng Shi;Yang Du
本文将右预条件广义最小留数（GMRES-RP）方法应用于一维海面电磁散射的分析。我们首先验证了GMRES-RP方法具有高精度，鲁棒性和效率的理想功能，因此，非常适合这样的分析。然后，我们进行了系统的分析，通过检查风速的影响，入射角，海洋频谱，以及重力和中间波的包容程度。在16384 λ的大表面长度和低于-70 dB的本底噪声下，我们发现了比文献中建议的更精细的结构：在近法向入射角（θi=20°）下，VV和HH结果对风速仍然敏感。在整个入射角范围内，小风速下的灵敏度高于中到高风速。Plant认为，随着风速的增加，中间波的贡献（而不是作为大波谱的一部分）变得越来越重要，因此需要多尺度模型。我们的数值分析验证了这一观点，表明归一化的双基地散射系数值高达4分贝，在某些角度的H极化在L波段可以归因于中间波和倾斜调制提供的大波。两尺度模型和三尺度模型的数值结果的比较进一步验证了这一观点，其中两尺度模型在前向散射角方面显示出明显的差异，而三尺度模型与矩量法显示出非常好的一致性，从而表明了在传统的两尺度模型之外推进多尺度模型的必要性。这一发现也意味着需要使用足够大的表面长度的数值研究，至少包括中间波，甚至低于中间入射的情况下。
In this paper, we apply the right preconditioned generalized minimal residue (GMRES-RP) method for the analysis of electromagnetic scattering from 1-D ocean surfaces. We first verify that the GMRES-RP method has the desirable features of high accuracy, robustness, and efficiency, and, hence, is well suited to such analysis. We then carry out this analysis systematically by examining the effects of wind speed, incidence angle, ocean spectrum, and the degree of inclusion of the gravity and intermediate waves. With a large surface length of 16384 λ and a noise floor pushed down below -70 dB, we have found more refined structures than suggested in the literature: At near-normal incidence angle (θi=20°), both VV and HH results remain sensitive to wind speed. Across the incidence angle range, the sensitivity is higher at small wind speed than at medium to high wind speed. Plant argued that the contribution from intermediate waves separately, not as a part of the large wave spectrum, becomes increasingly important with increasing wind speed and, accordingly, a multiscale model is desired. Our numerical analysis validates this viewpoint by showing that a normalized bistatic scattering coefficient value as large as 4 dB at certain angles for H-pol at L band can be attributed to the intermediate wave and the tilt modulation provided by large waves. The viewpoint is further validated by a comparison of the two-scale model and three-scale model against numerical results where the two-scale model shows appreciable discrepancy in the forward scattering angles whereas the three scale model shows very good agreement with MoM, hence manifesting the necessity of advancing multiscale models beyond the conventional two-scale model. This finding also implies the need for numerical studies to use adequately large surface length, at least to cover the intermediate waves, even for below intermediate incidence cases.