共查询到20条相似文献，搜索用时 15 毫秒
1.
针对机载合成孔径雷达(SAR)对海探测特点,采用多入射角法从SAR数据本身得到与海浪参数反演区域时空匹配的同步海面风速和风向,并结合线性变换关系,计算得到海浪初猜谱对应的仿真SAR图像谱,将仿真SAR图像谱和观测SAR图像谱输入代价函数中进行迭代运算,通过非线性方程的解算得到最适海浪谱;采用交叉谱法去除海浪传播180°方向模糊,最终得到海浪参数。论文提出的基于同步风场的机载SAR海浪参数反演方法,充分利用了机载SAR海洋环境探测的优势,解决了传统SAR海浪参数反演中初猜谱构造依赖外部风场的问题,机载同步飞行试验的海浪参数反演结果与浮标观测值的有效波高、波向的均方根误差分别为0.23 m和13.23°,验证了该方法的有效性,可为机载SAR海浪参数反演业务化提供支持。 相似文献
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Satellite-based RAR performance simulation for measuring directional ocean wave spectrum based on SAR inversion spectrum 总被引：1，自引：0，他引：1
Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence. Both them have their own advantages and limitations. Scientists hope that SAR and satellite-based RAR can complement each other for the research on wave properties in the future. For this study, the authors aim to simulate the satellite-based RAR system to validate performance for measuring the directional wave spectrum. The principal measurements are introduced and the simulation methods based on the one developed by Hauser are adopted and slightly modified. To enhance the authenticity of input spectrum and the wave spectrum measuring consistency for SAR and satellite-based RAR, the wave height spectrum inversed from Envisat ASAR data by cross spectrum technology is used as the input spectrum of the simulation system. In the process of simulation, the sea surface, backscattering signal, modulation spectrum and the estimated wave height spectrum are simulated in each look direction. Directional wave spectrum are measured based on the simulated observations from 0° to 360°. From the estimated wave spectrum, it has an 180° ambiguity like SAR, but it has no special high wave number cut off in all the direction. Finally, the estimated spectrum is compared with the input one in terms of the dominant wave wavelength, direction and SWH and the results are promising. The simulation shows that satellite-based RAR should be capable of measuring the directional wave properties. Moreover, it indicates satellite-based RAR basically can measure waves that SAR can measure. 相似文献
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This work examines ERS-1 (the first European Remote Sensing Satellite) SAR (Synthetic Aperture Radar) water surface wave images over Hualien of Taiwan, indicating that the variation of SAR signals in space domain is similar to in situ wave data's in time domain. Some statistical properties of SAR data are investigated. The Rayleigh distribution function closely corresponds with the histogram of wave heights, but the Gaussian one cannot for water surface displacements. Evidence reveals that SAR wave signals do not respond well to actual ocean waves effectively. As wave spectral analysis of available SAR data reveals, the appropriate sample size of SAR wave image, sampling average, and moving average should be taken carefully to accurately confirm directional power spectra. Moreover, SAR spectra are compared with in situ ones, confirming that peak frequencies correlate well and wave directions approximately agree with each other. Some differences between both spectral shapes remain somewhat unclear and require further study. Nevertheless, in this study, ERS-1 SAR power spectra verified the feasibility of deriving an appropriate dominant wave direction and peak frequency. 相似文献
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1 .Ｉｎｔｒｏｄｕｃｔｉｏｎ1ＴｈｉｓｓｔｕｄｙｗａｓｓｕｐｐｏｒｔｅｄｂｙＮＳＣｉｎＴａｉｗａｎｕｎｄｅｒｔｈｅｐｒｏｊｅｃｔＮｏ .ＮＳＣ 89 2 611 Ｅ 0 0 6 0 4 0 . Ｃｏｒｒｅｓｐｏｎｄｉｎｇａｕｔｈｏｒ.Ｅ ｍａｉｌ:ｄｊｄｏｏｎｇ @ｐｃｈｏｍｅ .ｃｏｍ .ｔｗ Ｏｃｅａｎｗａｖｅｓ ,ｗｈｉｃｈａｒｅｅｘｔｒｅｍｅｌｙｒａｎｄｏｍ ,ａｒｅｄｉｒｅｃｔｌｙａｎｄｉｎｄｉｒｅｃｔｌｙｄｅｐｅｎｄｅｎｔｏｎｍｅｔｅｏｒｏｌｏｇｉ ｃａｌ,ｈｙｄｒｏｌｏｇｉｃａｌ,ｏｃｅａｎｏｇｒａｐｈｉｃａｎｄｔｏｐｏｇ… 相似文献
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Dynamical analysis of mesoscale eddy-induced ocean internal waves using linear theories 总被引：3，自引：1，他引：2
This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features. 相似文献
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基于哨兵一号和高分三号卫星SAR数据的马六甲海峡内孤立波特性研究 总被引：2，自引：0，他引：2
漫长狭窄的马六甲海峡是重要的航道，研究该海峡内孤立波特征对潜艇、船只航行和海洋工程都是急需解决的问题。利用高空间分辨率的哨兵1号（Sentinel-1）和高分三号（GF-3）SAR遥感数据，对马六甲海峡的内孤立波特征开展了详细研究。利用哨兵一号2015年6月到2016年12月20景有内孤立波的SAR图像和高分三号2018年4月到2019年3月24景有内孤立波的SAR图像，统计分析了马六甲海峡海域的内孤立波空间分布特征。发现内孤立波多以内孤立波包以及单根内孤立波形式出现，内孤立波头波的波峰线最长可达39km。采用高阶非线性薛定谔方程反演模型可以计算出内孤立波的振幅与群速度，计算得到的内孤立波振幅和波包的传播群速度分别为4.7m ~ 23.9m和0.12m/s ~ 0.40m/s。由KdV方程得到的单根内孤立波的相速度为0.26m/s ~ 0.60m/s。可以得到，马六甲海峡内孤立波的振幅与传播速度与地形密切相关。 相似文献
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Oceanic pycnocline depth retrieval from SAR imagery in the existence of solitary internal waves 总被引：2，自引：1，他引：1
Oceanic pycnocline depth is usually inferred from in situ measurements. It is attempted to estimate the depth remotely. As solitary internal waves occur on oceanic pycnocline and propagate along it, it is possible to retrieve the depth indirectly in virtue of the solitary internal waves. A numerical model is presented for retrieving the pycnocline depth from synthetic aperture radar （SAR） images where the solitary internal waves are visible and when ocean waters are fully stratified. This numerical model is constructed by combining the solitary internal wave model and a two-layer ocean model. It is also assumed that the observed groups of solitary internal wave packets on the SAR imagery are generated by local semidiurnal tides. A case study in the East China Sea shows a good agreement with in situ CTD （conductivity-temperature-depth） data. 相似文献
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Liu A.K. Ramp S.R. Yunhe Zhao Tswen Yung Tang 《Oceanic Engineering, IEEE Journal of》2004,29(4):1144-1156
During the recent Asian Seas International Acoustics Experiment (ASIAEX), extensive current meter moorings were deployed around the continental shelf-break area in the northeastern South China Sea. Thirteen RADARSAT SAR images were collected during the field test to integrate with the in situ measurements from the moorings, ship-board sensors, and conductivity/temperatire/depth (CTD) casts. Besides providing a synoptic view of the entire region, satellite imagery is very useful for tracking the internal waves, locating surface fronts, and identifying mesoscale features. During ASIAEX in May 2001, many large internal waves were observed at the test area and were the major oceanic features studied for acoustic volume interaction. Based on the internal wave distribution maps compiled from satellite data, the wave crests can be as long as 200 km with an amplitude of 100 m. Environmental parameters have been calculated based on extensive CTD casts data near the ASIAEX area. Nonlinear internal wave models have been applied to integrate and assimilate both synthetic aperture radar (SAR) and mooring data. Using SAR data in deep water as an initial condition, numerical simulations produced the wave evolution on the continental shelf and compared reasonably well with the mooring measurements at the downstream station. The shoaling, turning, and dissipation of large internal waves at the shelf break have been studied and are very important issues for acoustic propagation. 相似文献
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合成孔径雷达是海洋内波研究中最重要的工具之一。雷达图像中的斑点噪声会严重降低图像的质量,这一问题在处理和分析信号较弱的二模态内波信号和上升型内波信号时极为明显。合成孔径雷达图像中的海洋内孤立波的信号具有明显的尺度性和方向性。同时,curvelet变换作为一种同时具备尺度分辨率和方向分辨率的数学变换,能够对一幅雷达图像在不同尺度、不同方向和不同位置上进行分析。本文给出了一个基于curvelet变换的合成孔径雷达海洋内孤立波图像的斑点噪声抑制方法。该方法可简述为：(1)对一幅合成孔径雷达海洋内孤立波图像进行curvelet变换,获得curvelet系数;(2)分别仅仅保留一个尺度的系数,将其它尺度的系数置为零,利用处理之后的系数分别重建图像,得到仅仅用一个尺度的系数重建的图像;(3)分别计算上一步中得到的图像的均方差,根据波浪理论,图像的方差代表能量,方差越大则能量越大,以此可以确定内波信息集中的尺度;(4)在每个尺度下,分别计算每个方向的curvelet系数矩阵的平均值,以此确定内孤立波信号集中的方向;(5)在上两步工作的基础上,仅仅保留内波信号集中的尺度和方向的系数,而将其它尺度和方向的系数置为0,得到一幅提取主波信息的图像;(6)将上一步得到的提取主波信息的图像加回到原始图像中,从而达到增强波浪信息并抑制斑点噪声的目的。大量的实验验证表明,该方法不仅能有效地压制斑点噪声,而且能有效地增强波浪信号。 相似文献
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The measurement of internal-wave signatures using synthetic aperture radar (SAR) or real aperture radar (RAR) techniques is an emerging technology that offers a viable means of locating and tracking surface ship wakes by their unique signatures. Under the assumption that the image measured by the radar is dominated by the underlying dynamics of the internal wave, we develop model-based techniques for enhancement based on a recently developed generic dispersive-wave processor. Using images synthesized by a sophisticated propagation model, it is shown that the processor not only offers a unique approach compared to the more traditional image-processing techniques that do not incorporate the propagation model, but is also capable of providing reasonable enhancement of the noisy measurements 相似文献
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Extraction of coastal ocean wave fields from SAR images 总被引：3，自引：0，他引：3
《Oceanic Engineering, IEEE Journal of》2005,30(3):526-533
Wave spectra derived from synthetic aperture radar (SAR) images acquired by ENVISATs are compared to in situ measurements by seven sensors, deployed in a field experiment carried out on the French coast of La Manche (English Channel). The wave spectra inversion scheme is adapted for shallow water from the European Space Agency (ESA)'s operational processing techniques used for level 2 ocean wave products. Under the low to moderate wind speed observed conditions, overall good agreement is found between in situ and SAR observations over a wide range of wave heights and directions, including waves propagating in the radar azimuth direction and incidence angles different from the standard imagette products. 相似文献
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多模式小卫星SAR（synthetic aperture radar,合成孔径雷达）是一种搭载于小卫星平台的新体制雷达系统,它集SAR、散射计、高度计、波谱仪4种遥感器的优势于一身。它可以根据需求分时实现几种工作模式的切换,可兼顾对海洋目标和海洋动力环境的高精度测量。由于卫星发射存在诸多不确定因素,为了在卫星发射前对多模式小卫星SAR进行检验,本文对拟开展的机载挂飞试验进行了介绍。首先,介绍了拟开展的机载挂飞试验的等效性原则。接下来,介绍了各种工作模式试验、SAR/散射计联合反演试验、多视向SAR试验的飞行路线规划。之后,介绍了机载挂飞试验的雷达参数设计方法。最后,给出了各种工作模式的雷达参数设计结果。所设计的飞行路线和雷达参数可以为机载挂飞试验服务,并且实现了星载技术指标的准等效验证。通过小卫星SAR卫星组网可弥补目前SAR卫星时间分辨率低的缺点。 相似文献
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The literature contains theoretical derivation of the internal wave generation techniques by using control volume approach. The source term in three-dimensional continuity equation is derived by Reynolds transport theorem. The source term in two-dimensional wave model is derived by work-energy equation. The results confirmed that the appropriate velocity to be included in the source term is physically the group velocity which is the energy velocity for a wave model. 相似文献
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S. F. Dotsenko 《Physical Oceanography》1997,8(6):369-379
The paper addresses the plane linear problem on generation of an internal wave in a continuously stratified ocean by a moving
atmospheric front. The front exhibits air pressure perturbations, as well as the field of tangential wind stress. In the frame
of a model for the planetary atmospheric boundary layer, a relationship between the air pressure and wind fields has been
derived, generalizing Ackerbloom's formulae for the case of a moving atmospheric anomaly. Using the Fourier transform, a relation
has been obtained for the wave's signature in the wake of a moving atmospheric perturbation, and the respective analysis has
been performed. Numerical estimates of the internal wave amplitudes have been acquired for the mean density stratification
in the Kuril-Kamchatka region. Comparative analysis of the effectiveness of wave signature generation by the moving areas
of surface pressures and tangential wind stresses has been carried out. It has been demonstrated that the latter field determines
the effectiveness of baroclinic wave signature generation.
Translated by Vladimir A. Puchkin. 相似文献
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以考虑了地转和均匀背景流场影响的两层流体界面内波频散关系模型为基础,得到新的利用SAR遥感图像计算混合层深度的方法。利用该方法对一幅南海北部SAR内波图像进行了实例研究,并且和时空同步的CTD资料进行了对比。结果表明,加入地转和均匀背景流场影响的模型更为合理,为更准确地反演混合层深度奠定了基础。 相似文献
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本文运用基于自适应网格的流体动力学开源软件Gerris,来建立基于Boussinesq近似下的二维不可压缩Euler方程组的数值模型,以模拟不同层化条件下稳定状态的完全非线性大振幅内孤立波。文中比较了完全非线性的用Gerris实现的Euler模型与弱非线性的KdV理论模型在刻画大振幅内孤立波结构及特征参数上的差异,说明在模拟大振幅内孤立波时,高阶非线性不应忽略。Euler模型模拟结果表明,完全非线性大振幅内孤立波的等密度面半宽度随深度变化,这使得基于KdV方程解析解、利用卫星SAR(Synthetic Aperture Radar)图像提取内孤立波极值间距来反演内波振幅的可行性存疑,需要重新评估。此外,本文用两组实测数据验证了用Gerris实现的Euler模型模拟大振幅内波的有效性。 相似文献
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A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅰ. Simulation of internal tide transformation 总被引：1，自引：0，他引：1
For settlement of the well-known problem of contemporary radar imaging models, i. e. , the problem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal waters at high radar frequency bands （ X-band and C-band）, the impact of the ocean surface mixed layer turbulence and the significance of strat- ified oceanic model on SAR remote sensing of internal solitary waves are proposed. In the north of the South China Sea by utilizing some observed data of background field the nonlinearity coefficient, the dispersion coefficient, the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately. Through simulations of internal tide transfor- mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of internal wave field are obtained. The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m, but the maximum current speeds take place at depth 20 m in this area of the sea （about 20°30＇N, 114°E） in August. It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation. The obtained results provide the possibility for the simulation of SAR signatures of internal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper. 相似文献