干涉合成孔径雷达海浪遥感理论与应用研究

IOCAS-IR > 海洋环流与波动重点实验室

	干涉合成孔径雷达海浪遥感理论与应用研究
其他题名	Theoretical and Application Study of Remoting Sensing Ocean Wave by Interferometric Synthetic Aperture Radar
	张彪
学位类型	博士
	2008-06-11
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	干涉合成孔径雷达海浪遥感数值模拟参数化反演模式
摘要	干涉合成孔径雷达 (Interferometric Synthetic Aperture Radar，InSAR) 是以合成孔径雷达复数据提取的相位为信息源获取地表三维信息和海表散射体运动信息的新型微波成像雷达。 InSAR通过两幅天线同时观测 (单轨模式)，或两次近平行的观测 (重复轨道模式)，获取地面或海面同一景观的复图像对。20世纪90年代以来，InSAR陆地和海洋研究成为微波遥感的热点，广泛应用于地表变形监测、南极冰流测量、地面或海面慢速运动目标检测等领域。近年来，国际上逐渐应用机载顺轨或交轨干涉合成孔径雷达进行海表面流速测量以及海面波成像机制研究。相对于传统单天线合成孔径雷达 (Synthetic Aperture Radar, SAR)，双天线干涉合成孔径雷达 (InSAR) 测量海表面波有着独特的优势： (1) InSAR复图像的相位近似正比于海面散射体的径向速度，这种内在的成像机制提供了直接测量海表面动态运动的机会。 (2) 真实孔径雷达调制传递函数几乎对InSAR相位图像没有影响，而对传统SAR图像影响较大。基于干涉合成孔径雷达测量海浪的优势，本文做了一些干涉合成孔径雷达海浪遥感理论与应用研究工作，主要内容大致可归纳如下： (1)基于新建立的顺轨干涉合成孔径雷达 (Along-Track Interferometric Synthetic Aperture Radar，ATI-SAR) 相位谱与海浪谱之间的非线性映射关系，通过数值模拟研究了不同雷达参数和海况参数对应的ATI-SAR相位谱。数值模拟结果表明：距离速度比率、雷达入射角、天线间距和有效波高和波长比率是影响ATI-SAR海浪成像的重要因素。进一步，利用机载X波段水平极化相位图像和机载C波段水平极化相位图像谱结合方向波骑士浮标测量的海浪方向谱验证了ATI-SAR相位谱与海浪谱之间的非线性映射关系。结果显示用前向映射关系计算的相位谱与实际观测的相位谱较为一致，二者相关系数总体大于0.6，而且对成像非线性不敏感. (2)建立了包含海表面高度和速度聚束的交轨干涉合成孔径雷达 (Across-Track Interferometric Synthetic Aperture Radar，XTI-SAR) 涌浪干涉相位模型，得到了涌浪成像的解析表达式，进一步研究了XTI-SAR沿方位向传播的涌浪成像机制。定义二次谐波振幅与基波振幅比率来表征成像非线性，通过比较XTI-SAR和ATI-SAR相位的二阶调和分量，分析不同海况和干涉SAR参数情况下的数值模拟，结果表明：当速度聚束弱时，XTI-SAR相位比ATI-SAR相位具有较强的非线性，ATI-SAR比XTI-SAR更适合测量海浪。当速度聚束强时，XTI-SAR相位比ATI-SAR相位具有较弱的非线性，XTI-SAR比ATI-SAR更适合测量海浪。 (3)基于包含海表面高度和速度聚束的交轨干涉合成孔径雷达 (XTI-SAR) 涌浪干涉相位模型，结合多维高斯变量的特征函数方法建立了新的XTI-SAR相位谱与海浪谱非线性积分变换。新积分变换不同于Bao (1999) 建立的积分变换，两者形式上区别在于新积分变换中包含了长波径向轨道速度一阶倒数项。数值模拟显示：通常情况下，长波径向轨道速度一阶倒数项不能忽略。进一步，我们针对不同雷达参数和海况结合新非线积分变换对XTI-SAR海浪成像进行了数值模拟，结果表明：同顺轨干涉合成孔径雷达 (ATI-SAR) 海浪成像一致，距离速度比率和有效波高与波长比率是影响XTI-SAR海浪成像的重要因子。 (4)基于新的ATI-SAR相位谱与海浪谱之间的非线性映射关系，发展了利用ATI-SAR相位图像反演海浪方向谱的参数化反演模式，并由此得到海浪波长、波向和有效波高。反演结果与现场浮标观测结果比较一致。相对于其它反演模式，参数化反演模式的优点在于：(1) 不需要任何附加信息如初猜海浪谱、散射计提供的风速风向等信息。 (2) 不需要对相位图像进行辐射定标，可以由反演的海浪谱直接计算有效波高。(3) 反演结束后还可以得到成像区域的局地风速信息。因此，参数化反演模式可以实现风、浪信息的联合反演。
其他摘要	Interferometric synthetic aperture radar (InSAR) is new microwave imaging radar that can obtain information about three-dimensional earth surface and movement of sea surface scattering. The source of information is the phase extracted from the complex data of synthetic aperture radar. InSAR system acquires a pair of complex images of earth or sea surface by using two antennas to observe at same time (single pass mode) or at two parallel paths (repeat-pass mode). Since 1990s, studying on land and ocean with InSAR has become a hot spot of microwave remote sensing. InSAR has widely used in surface deformation monitoring, measurement of Antarctic ice streams, detection of slowly moving target on ground or sea surface. Recently, along-track or across-track interferometric synthetic aperture radar has been gradually used to measure sea surface current velocity and study imaging mechanism of sea surface waves. InSAR has two advantages to measure ocean surface waves over the conventional SAR: (1) The phase of the complex InSAR image is approximately proportional to the radial velocity of the sea surface, and thus the InSAR inherent imaging mechanism offers the opportunity to measure the dynamic motions of the sea surface directly. (2) The real aperture radar modulation transfer function (RAR-MTF) has practically no effect on the InSAR phase image, but seriously affect the conventional SAR image. Based on the advantages of InSAR measurement of sea surface waves, we have done some research work about theoretical and applicaitonal study of remoting sensing ocean waves by interferometric synthetic aperture radar. The main content can be summarized as following: (1) Based on the new nonlinear integral transform between along-track interferometric synthetic aperture radar (ATI-SAR) phase spectra and ocean wave spectra, ATI-SAR phase spectra are calculated for various sea states and radar configurations. The numerical simulations show that the slant range to velocity ratio, the radar incident angle, the baseline, the significant wave height to wavelength ratio affect ATI-SAR imaging ocean waves. The ATI-SAR imaging theory is validated by means of X-band, HH-polarized ATI-SAR phase images and C-band, HH-polarized ATI-SAR phase image spectra of ocean waves. It is shown that ATI-SAR phase image spectra calculated by forward mapping are well in agreement with available ATI-SAR observations. ATI-SAR spectral correlation coefficients betweenobserved and simulated are greater than 0.6 and are not sensitive to the degree of nonlinearity. (2) We establish an interferometric phase model of swell for the across-track interferometric synthetic aperture radar (XTI-SAR) with ocean surface elevation and velocity bunching. An analytical presentation of swell imaging by XTI-SAR is derived. The imaging mechanism of swell propagating in azimuth direction is further investigated. The ratio of the amplitude of the second harmonic and that of the foundamental wave is used to represent the nonlinearity of the imaging. By comparing the second order harmonic components of XTI-SAR phase and that of ATI-SAR phase, analyzing numerical simulations for different sea states and typical interferometric SAR parameters, it is found that XTI-SAR phase suffers stronger nonlinear distortion than ATI-SAR phase when velocity bunching is weak, so ATI-SAR is more appropriate than XTI-SAR to measure ocean wave. Otherwise, when velocity bunching is strong, ATI-SAR phase suffers stronger nonlinear distortion than XTI-SAR phase, XTI-SAR is more suitable than ATI-SAR to measure ocean wave. (3) We present a new nonlinear integral transform relating the ocean wave spectra to the XTI-SAR phase image spectra. Firstly, a phase model is proposed for the XTI-SAR phase includes ocean surface elevation and velocity bunching. Then, a new nonlinear integral transform is derived based on the phase model and the characteristic method function. The new transform differs from the one previously derived by Bao (1999) by an additional term containing the derivative of the radial component of the orbital velocity associated with the long ocean waves. The numerical simulations show that, in general, the additional term can not be neglected. Furthermore, XTI-SAR phase image spectra are estimated for different sea states and radar configurations. We demonstrate that the slant range to velocity ratio and significant wave height to ocean wavelength ratio are crecial factors to affect the XTI-SAR imaging ocean wave. (4) Based on the new nonlinear mapping between ATI-SAR phase spectra and ocean wave spectra, we develop a parametric algorithm to retrieve ocean wave spectra by means of ATI-SAR phase image. Furthermore, the wavelength and wave direction, as well as significant wave height are derived from the parametric algorithm. These retrieval parameters are well in agreement with the in situ buoy observations. The advantages of the parametric algorithm are given as following: (1) it does not require any additional information about first-guess ocean wave spectra from ocean wave model and wind velocity from scatterometer.(2) ATI-SAR phase image does not need to radiometric calibration, significant wave height can be directly calculated from the retrieval ocean wave spectra. (3) Wind speed of local imaging area is also derived when the retrieval process finished. Therefore, the parametric retrieval algorithm is able to achieve the joint retrieval of wind and wave information.
页数	121
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1209
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	张彪. 干涉合成孔径雷达海浪遥感理论与应用研究[D]. 海洋研究所. 中国科学院海洋研究所,2008.

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