共查询到19条相似文献，搜索用时 578 毫秒
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采用结合匹配法和经验正交函数法的射线声层析反演方法,针对流场水平分布不均匀特点,使用距离等效分段方法对反演算法进行改进,利用三个断面声层析数据,对胶州湾口潮流场的垂直和水平分布进行反演。与传统方法比较,大大降低与实测流速垂直分布间的偏差,平均偏差小于0.02 m/s,流场垂直分布间的相关系数提高到0.85以上。分析了声传播断面上不同的流场结构,以及涨潮期间在胶州湾团岛附近出现的涡流现象,并计算得到湾口海水流量变化。结果表明,改进的射线声层析反演方法可有效地用于水平分布不均匀流场监测,仅采用少量声学观测站位,即可获得大范围的复杂流场三维信息,有利于近海海洋资源开发、海洋环境保护和船舶航行安全。 相似文献
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本文利用三维数值模型(ROMS-Co Si NE)分析了整个加利福尼亚流系水平流场的季节性演变过程,研究了美国加州中部海域流场垂直结构的季节性变化特征,并探讨了其动力学机制。研究发现:(1)数值模型能够较为准确的模拟流场的季节性变化,与浮标观测数据以及前人的研究结果符合良好;(2)从表层到200m,加利福尼亚潜流向高纬度扩张,近岸上升流急流则向高纬度撤退,加州南部海域的中尺度涡更显著;(3)在加州中部海域,近岸急流的最大值(约15cm/s)发生在夏季,位于近岸的表层海域;加利福尼亚潜流最大值(约4cm/s)发生于冬季,出现在离岸100km的125m处;加利福尼亚流在春季达到全年最大值(约5cm/s),流轴位于离岸(400—600km)的表层海水。加利福尼亚流系的流场具有显著的季节性变化,研究进一步表明这主要受地转关系调控。 相似文献
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海洋声层析是1979年美国科学家W.Munk等人提出的,通过测量传播时间等声传播信号有关参量反演声波所穿越的海洋特征,得到大面积海域中的海洋动力学状态及其变化的估计。声层析方法自提出以来受到各国的重视。在最初的20 a间,以全球测温计划(ATOC)为代表的一系列验证实验推动了声层析的理论研究、设备研制和应用。步入21世纪后,声层析与海洋动力学的数据同化、利用滑翔机等设备的移动声层析以及沿海声层析得到重视,并进行了相关的理论与实验研究。纳入成像旗下的声层析希尔伯特方法、有效低功耗的分布式传感网络声层析,以及被动声层析,或将成为声层析未来研究的重要方向。 相似文献
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基于Argo历史观测的南海海盆尺度中层流场研究 总被引：1，自引：0，他引：1
针对南海海域海流环境复杂、中层实测数据量少的现状，本文基于2006-2016年布放在南海海域的114个Argo剖面浮标的卫星定位等信息，采用基于背景流和惯性流外推的最小二乘方法，获取南海海域1 200 m深中层流场信息，并采用Divand变分插值的方法形成网格化季节流场。结果表明:（1）针对南海中层（1 200 m）流场，单个Argo浮标可以刻画出具体的中尺度结构，如越南沿岸的反气旋涡，半径约为120 km，最大流速约为9.6 cm/s，平均流速为5.3 cm/s；（2） Argo网格化流场表明海盆尺度中层流场南海南部为反气旋环流结构，北部为气旋式环流，同时在吕宋海峡口存在从南海至太平洋的水体交换；（3）将该流场信息与HYCOM和YoMaHa'07两种资料对比，吻合度较高，与HYCOM再分析资料的偏差分布趋近于正态分布，海流的东西向分量的均方根误差为3.28 cm/s，南北向分量的均方根误差为3.26 cm/s。总体而言，利用Argo轨迹资料能够有效地反演出南海地区海盆尺度的中层环流特征。 相似文献
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海洋表面流场是海洋科学研究中需要着重考虑的环境参数,近实时的海洋表面流场精细化测量对海洋学研究有着重要意义,但是目前大多数海洋表面流场观测技术难以同步实现大范围近实时的海洋表面流场观测。文中在简要对比各类海洋表面流场测量方法的基础上,重点介绍了基于水色遥感图像观测反演海洋表面流场的鲁棒光流算法,该算法在流场计算过程中,能很好地保留流场细节信息。为直观验证本文测量方法的可靠性,文中提供了海洋表面流场的分析实例,同时给出了美国国家航空航天局(NASA)提供的OSCAR流场数据,对文中算法的可靠性进行了验证。 相似文献
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基于CCMP风场资料,采用无结构网格、浪-流双向实时耦合模型FVCOM-SWAVE,模拟强热带风暴"米雷"在中国近海区域产生的海浪场,将耦合模型模拟的有效波高和平均周期与实测浮标资料进行比对,发现模拟结果的各类误差总体较小,说明耦合模型能够较好地模拟考虑浪流相互作用下中国近海台风浪过程。对比考虑潮汐引起的水位变化与不考虑水位变化情况下对耦合模型模拟结果的影响,发现在近岸区域考虑潮水位情况下的有效波高和平均周期模拟结果周期性特征明显,说明潮汐对耦合模型在近岸处有效波高的模拟影响显著。 相似文献
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This paper applies a full-field technique to invert bottom sound profile and bottom reflectivity from simulated acoustic data in a shallow water environment. Bottom sound-speed profile and bottom reflectivity have been traditionally estimated using seismic reflection/refraction techniques when acoustic ray paths and travel time can be identified and measured from the data. However, in shallow water, the many multipaths due to bottom reflection/refraction make such identification and measurement rather difficult. A full-field inversion technique is presented here that uses a broad-band source and a vertical array for bottom sound-speed and reflectivity inversion. The technique is a modified matched field inversion technique referred to as matched beam processing. Matched beam processing uses conventional beamforming processing to transform the field data into the beam domain and correlate that with the replica field also in the beam domain. This allows the analysis to track the acoustic field as a function of incident/reflected angle and minimize contamination or mismatch due to sidelobe leakage 相似文献
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Chapman N.R. Chin-Bing S. King D. Evans R.B. 《Oceanic Engineering, IEEE Journal of》2003,28(3):320-330
Inversion methods have been developed over the past decade to extract information about unknown ocean-bottom environments from acoustic field data. This paper summarizes results from the Office of Naval Research/Space and Naval Warfare Systems Command (SPAWAR) Geoacoustic Inversion Techniques Workshop, which was designed to benchmark present-day inversion methods. The format of the workshop was a blind test to estimate unknown geoacoustic profiles by inversion of synthetic acoustic field data. The fields were calculated using a high-angle parabolic approximation and verified using coupled normal modes for three range-dependent shallow-water test cases: a monotonic slope; a shelf break; and a fault intrusion in the sediment. Geoacoustic profiles were generated to simulate sand, silt, and mud sediments in these environments. Several different approaches for inverting the acoustic field data were presented at the workshop: model-based matched-field methods; perturbation methods; methods using transmission loss data; and methods using horizontal array information. An effective inversion must provide both an estimate of the bottom parameters and a measure of the uncertainty of the estimated values. New methods were presented at the workshop to formalize the measure of uncertainty in the inversion. Comparisons between the different inversions are discussed in terms of a metric-based transmission loss calculated using the inverted profiles. The results demonstrate the effectiveness of present-day inversion techniques and indicate the limits of their capabilities for range-dependent waveguides. 相似文献
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This paper presents the results of a perturbative inverse approach applied to the range-dependent acoustic data provided as part of the Geoacoustic Inversion Techniques Workshop. The method is based on the Hankel transform relationship between complex-pressure field data measured on a horizontal array and the depth-dependent Green's function for a horizontally stratified medium. The input data to the inversion algorithm are discrete values of horizontal wavenumbers estimated for locally range-independent subapertures of the acoustic data. Inversion results are presented with emphasis placed on inverting for compressional wave speed as a function of both range and depth in the bottom. 相似文献
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The paper discusses an inversion method that allows the rapid determination of in situ geoacoustic properties of the ocean bottom without resorting to large acoustic receiving apertures, synthetic or real. The method is based on broad-band waterborne measurements and modeling of the waveguide impulse response between a controlled source and a single hydrophone. Results from Yellow Shark '94 experiments in Mediterranean shallow waters using single elements of a vertical array are reviewed, inversion of the bottom parameters is performed with an objective function that includes the processing gain of a model-based matched filter (MBMF) receiver relative to the conventional matched filter. The MBMF reference signals incorporate waveguide Green's functions for known geometry and water column acoustic model and hypothesized bottom geoacoustic models. The experimental inversion results demonstrated that, even for complex environmental conditions, a single transmission of a broad-band (200-800 Hz) coded signal received at a single depth and a few hundred forward modeling runs were sufficient to correctly resolve the bottom features. These included the sound speed profile, attenuation, density, and thickness of the top clay sediment layer, and sound speed and attenuation of the silty clay bottom. Exhaustive parameter search proved unequivocally the low-ambiguity and high-resolution properties of the MBMF-derived objective. The single-hydrophone results compare well with those obtained under identical conditions from matched-field processing of multitone pressure fields sampled on the vertical array. Both of these results agree with expectations from geophysical ground truth. The MBMF has been applied successfully to a field of advanced drifting acoustic buoys on the Western Sicilian shelf, demonstrating the general applicability of the inversion method presented 相似文献
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This paper describes a regularized acoustic inversion algorithm for tracking individual elements of a freely drifting sonobuoy field using measured acoustic arrival times from a series of impulsive sources. The acoustic experiment involved 11 sonobuoys distributed over an 8/spl times/6-km field, with a total of six sources deployed over 72 min. The inversion solves for an independent track for each sonobuoy (parameterized by the sonobuoy positions at the time of each source transmission), as well as for the source positions and transmission instants. Although this is a strongly under-determined problem, meaningful solutions are obtained by incorporating a priori information consisting of prior estimates (with uncertainties) for the source positions and initial sonobuoy positions and a physical model for sonobuoy motion along preferentially smooth tracks. The inversion results indicate that the sonobuoys move approximately 260-700 m during the source-deployment period. Closely spaced sonobuoys move along similar tracks; however, there is considerable variability in track directions over the entire field. Positioning uncertainties in horizontal coordinates are estimated using a Monte Carlo appraisal procedure to be approximately 100 m in an absolute sense and 65 m in a relative sense. A sensitivity study indicates that the uncertainties of the a priori position estimates are the limiting factor for track accuracy, rather than data uncertainties or source configuration. 相似文献
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A method is described for the estimation of geoacoustic model parameters by the inversion of acoustic field data using a nonlinear optimization procedure based on simulated annealing. The cost function used by the algorithm is the Bartlett matched-field processor (MFP), which related the measured acoustic field with replica fields calculated by the SAFARI fast field program. Model parameters are perturbed randomly, and the algorithm searches the multidimensional parameter space of geoacoustic models to determine the parameter set that optimizes the output of the MFP. Convergence is driven by adaptively guiding the search to regions of the parameter space associated with above-average values of the MFP. The performance of the algorithm is demonstrated for a vertical line array in a shallow water enviornment where the bottom consists of homogeneous elastic solid layers. Simulated data are used to determine the limits on estimation performance due to error in experimental geometry and to noise contamination. The results indicate that reasonable estimates are obtained for moderate conditions of noise and uncertainty in experimental geometry 相似文献
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基于正交匹配追踪的声层析方法 总被引：2，自引：0，他引：2
声速剖面的变化会对声传播产生较大的影响，经验正交函数模型经常用来实现对声速剖面数据的简化描述。然而在内波、湍流等海水不均匀性存在时，这种正则化操作会造成声速重构精度的大幅降低。本文利用字典学习生成声速剖面的非正交原子，在稀疏编码时采用正交匹配追踪（OMP，Orthogonal Matching Pursuit）算法，更新字典则使用KSVD （Kernel Singular Value Decomposition）的字典更新算法。由于字典学习不需要强制使用正交条件，对于训练数据更加灵活，从而可以使用少数的原子组合达到更高的重构精度。利用一次浅海声学实验多次测量的声速剖面研究了海水声速剖面的经验正交函数表示和字典学习，研究表明：相比于正交函数表示，学习字典可以利用少数原子（甚至一个原子）更好的解释声速剖面扰动。字典学习可以提高声速剖面的稀疏性，从而提高声速剖面的反演精度。 相似文献
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It is extremely difficult to determine shallow ocean bottom properties (such as sediment layer thicknesses, densities, and sound speeds). However, when acoustic propagation is affected by such environmental parameters, it becomes possible to use acoustic energy as a probe to estimate them. Matched-field processing (MFP) which relies on both field amplitude and phase can be used as a basis for the inversion of experimental data to estimate bottom properties. Recent inversion efforts applied to a data set collected in October 1993 in the Mediterranean Sea north of Elba produce major improvements in MFP power, i.e., in matching the measured field by means of a model using environmental parameters as inputs, even using the high-resolution minimum variance (MV) processor that is notoriously sensitive and usually results in very low values. The inversion method applied to this data set estimates water depth, sediment thickness, density, and a linear sound-speed profile for the first layer, density and a linear sound-speed profile for a second layer, constant sound speed for the underlying half space, array depth, and source range and depth. When the inversion technique allows for the array deformations in range as additional parameters (to be estimated within fractions of a wavelength, e.g., 0.1 m), the MFP MV peak value for the Med data at 100 Hz can increase from 0.48 (using improved estimates of environmental parameters and assuming a vertical line array) to 0.68 (using improved estimates of environmental parameters PLUS improved phone coordinates). The ideal maximum value would be 1.00 (which is achieved for the less sensitive Linear processor). However, many questions remain concerning the reliability of these inversion results and of inversion methods in general 相似文献