共查询到19条相似文献，搜索用时 109 毫秒
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从射线声学和简正波声学的角度，概述了海洋声层析的基本理论，包括射线走时反演、简正波走时反演、简正波相位反演和简正波水平折射层析。海洋声层析以反演海水温度和流速为基础。还总结了声层析在海洋学研究中的应用。 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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胶州湾水域有机农药六六六分布及迁移 总被引：4，自引：3，他引：1
根据1979年的胶州湾水域调查资料，分析有机农药六六六（HCH）在胶州湾水域的分布、迁移和季节变化。分析结果表明，在一年中，胶州湾水域夏季HCH的污染严重，而春、秋季污染较轻。在时空分布上，春、夏、秋季整个胶州湾水域的HCH水平分布比较均匀，属于面污染源。HCH的表、底层含量都相近，水体的垂直分布均匀。整个胶州湾水域，春季HCH含量增加，夏季迭到高峰5．393～12．480μg／L，秋季降低到低值0．073～0．685μg／L，这与胶州湾的入湾河流的流量变化相一致。因此认为，农药HCH的使用导致胶州湾水域HCH含量的变化。 相似文献
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根据1979—1984年(缺少1980年)的胶州湾水域调查资料,分析了胶州湾水域有机农药六六六(HCH)的垂直分布,提出了六六六的水域迁移过程,研究结果表明,此过程出现3个阶段:从污染源把六六六输出到胶州湾水域、把六六六输入到胶州湾水域的表层、六六六从表层沉降到底层。在胶州湾,六六六的垂直分布按照时空分布来划分区域。在时间尺度上,一年中的春季、夏季和秋季;在空间尺度上,把胶州湾水域分为3部分水域:湾内、湾口和湾外。通过不同的时空区域六六六的垂直分布,进一步提出了六六六的水域迁移机制,阐明了六六六垂直分布的规律及原因。 相似文献
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根据1979年的胶州湾水域调查资料,分析重金属Cd在胶州湾水域的水平分布、垂直分布和季节变化。研究结果表明:在整个胶州湾水域,水质没有受到任何Cd的污染。在胶州湾和湾口水域只有两个Cd的来源。一个是来源于地壳岩石风化,通过陆地径流把重金属Cd注入胶州湾水域;另一个是来源于海底,经过海洋水流的作用把重金属Cd注入湾口水域。作者提出了重金属在水域的环境本底值结构:基础本底值、陆地径流的输入量和海洋水流的输入量,并且应用于胶州湾水域。作者认为在来源的迁移过程中,有陆地来源迁移和海底来源迁移。根据杨东方的水域迁移过程研究,陆地径流决定了Cd的表、底层质量浓度变化。 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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基于南海1998年夏季调查航次诊断计算的流函数场,选取越南以东偶极子发生海域,进行不同的声层析观测站位设置实验。模拟计算声线传播时间信息,然后应用基函数重建方法进行了流函数场的模拟反演研究,讨论了不同随机观测误差对反演结果的影响。研究结果表明该方法是可行的,在所选取的约833 km×833 km海域内,在观测海域外围配置19个声层析观测站位就能够很好地重构原流函数场,空间分辨率约为63.7 km,可以分辨模拟海域中尺度涡场结构,这是传统的基于海流计(CM)或声学多普勒剖面仪(ADCP)等观测方法所不能企及的。该观测技术和方法可以实际应用于近海大范围流场结构的遥感实时监测,为近海污染物等的扩散研究,海洋环境变化等提供实时观测流场资料。 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(2):140-149
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Dezhang Chu Dajun Tang Austin T.C. Hinton A.A. Arthur R.I. Jr. 《Oceanic Engineering, IEEE Journal of》2001,26(1):70-83
In acoustic tomographic system capable of performing in situ two-dimensional (2D) acoustic imaging of shallow water sediments is described. This system is capable of resolving inhomogeneities greater than 10 cm and differentiating sound-speed variations greater than 2%, A tomographic inversion is performed in a 2D vertical slice of about 1 m 2 (1 m×1 m) using three identical probes, with each consisting of 70 evenly distributed transducers. In normal deployments, two of the probes are oriented vertically and are separated by about 1 meter, and the third is positioned horizontally right above the two vertical probes. The additional horizontal probe greatly improves the horizontal resolution of the system compared to conventional crosshole tomographic setups. Numerical simulations are performed to evaluate the influences of arrival time detection error and transducer position error on the performance of the tomography system. For an arrival time of 500 ns (standard deviation) and a position error of 4 mm (standard deviation), sound-speed anomalies of greater than 0.8% can be correctly predicted near the upper portion (close to the horizontal probe) and are resolvable near the lower portion. A controlled laboratory experiment was conducted to evaluate the performance of the system. The location of a polyurethane block (Conap EN22) used as a known target is correctly predicted while the inverted sound speed is about 9% lower than that from its actual value. Field data taken from a saturated muddy site are presented and analyzed. The inverted mean sound speed and attenuation are about 1480 ms-1 and 20 dBm-1, respectively 相似文献
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Computer simulation of coastal acoustic tomography with four, five, seven and nine stations was applied to two-dimensional
vortex fields of horizontal domain 5 km × 5 km. Travel time data obtained in reciprocal directions between all pairs of acoustic
stations were analyzed to reconstruct the vortex fields by the stochastic inverse method, reduced to the damped least squares
method. The weighting factor appearing in the inverse analysis was determined by applying the L-curve method, in which a point
making both the size of estimated error ‖y - Ex‖ and solution ‖x‖ as small as possible in a balance is specified as an optimum.
The performance of this method was examined using two-dimensional vortex models which have different wavenumber spectra and
adding the random error of different levels to the travel time difference data y. This study suggests that in the selection
of the optimal weighting factor the horizontal section of the simulated tidal vortex fields can be well reconstructed by the
coastal acoustic tomography system composed of five to seven acoustic stations located in the periphery of the vortex fields.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(4):586-602
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基于大涡模拟和局部滤波同化方法的海洋环流模式 总被引：2，自引：1，他引：2
结合最小二乘法极值原理,提出了一种基于局部谱展开的滤波同化方法,把测量数据和数值计算过程中出现的高频短波滤掉,并将高度计数据同化到了求解过程中.结果既增加了数值稳定性,又提高了数值模拟的准确性.针对在海洋环流问题中水平的流动性质和垂直的不同的特点,我们还将大涡模拟的思想和直接涡黏的思想分别应用于水平方向和垂直方向,给出的方法是一种适用于海洋环流和浅水环流问题的大涡模拟湍流模式.对热带和北太平洋一年四季非定常季风作用下环流的数值模拟表明,提出的方法非常有效,数值结果与实际相当吻合. 相似文献
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The acoustical tomography scheme for inferring a three-dimensional sound-speed field within some area based on the measurements of horizontal refraction angles is reviewed. The numerical simulations made so far were based on the assumption of the adiabaticity of low-frequency mode propagation. In this paper, an inversion scheme is presented that accounts for the acoustic mode interaction. We found that, generally, the interaction weakly affects the horizontal refraction angle, and it can be accounted for by iterations. Numerical simulations for the case of an Atlantic “meddy” corresponding to a strong double channel stratification are presented. Only three iterations were required to retrieve the exact strong sound-speed-field inhomogeneity within an area of 500 km×500 km 相似文献