High-precision measurement of tidal current structures using coastal acoustic tomography

Zhang, Chuanzheng; Zhu, Xiaohua; Zhu, Ze-Nan; Liu, Wenhu; Zhang, Zhongzhe; Fan, Xiangtao; Zhao, Ruixiang; Dong, Menghong; Wang, Min

doi:10.1016/j.ecss.2017.05.014

Cited by 25 publications

(16 citation statements)

References 15 publications

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“…The proposed and conventional methods are referred to as the coast-fitting method (CFM) and the no coast method (NCM), respectively. A detailed explanation of the site and the experimental conditions can be found in the study by Zhang et al [14]. The NCM is based on the Fourier function expansion of two-dimensional current fields in the tomography domain and the tapered least squares method determined the expansion coefficients.…”

Section: Methodsmentioning

confidence: 99%

“…Mapping rapidly-varying current fields in coastal seas is a remarkable capability of CAT [7][8][9][10][11][12][13]. A CAT experiment with a horizontal resolution of 1.53 km was conducted in 2015 in the Dalian Bay, China, in which 51 sound transmission paths were constructed for 11 CAT stations [14]. The current fields were reconstructed while using conventional tomographic inversion based on Fourier function expansion with no coast constraints.…”

Section: Introductionmentioning

confidence: 99%

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Mapping Current Fields in a Bay Using a Coast-Fitting Tomographic Inversion

Chen

Zhu

Zhang

et al. 2020

Sensors

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Coast-fitting tomographic inversion that is based on function expansion using three types of normal modes (the Dirichlet, Neumann, and open boundary modes) is proposed to reconstruct current fields from the coastal acoustic tomography (CAT) data. The superiority of the method was validated while using CAT data that were obtained in 2015 in the Dalian Bay. The semidiurnal tidal and residual current fields were accurately reconstructed over the entire model domain surrounded by coasts and open boundaries. The proposed method was effective, particularly around the peripheral regions of the tomography domain and the near-coast regions outside the domain, where accurate results are not expected from the conventional inverse method based on function expansion by Fourier function series with no coast fittings. The error velocity for the semidiurnal tidal currents was 2.2 cm s−1, which was calculated from the root-mean-square-difference between the CAT-observed and inverted range-averaged currents that were obtained along the nine peripheral transmission paths. The error velocity for the residual currents estimated from the 12-h mean net residual transport at the bay mouth was 0.9 cm s−1. The errors were significantly smaller than the amplitude of the tidal and residual currents.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mapping Current Fields in a Bay Using a Coast-Fitting Tomographic Inversion

Chen

Zhu

Zhang

et al. 2020

Sensors

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“…Initially, more comprehensive, multi-station measurements with CAT systems (more than five stations) were conducted by the Hiroshima University Group initially [ 6 , 7 , 8 , 9 ]. Of note, CAT has been highly applied in measuring various coastal–sea phenomena, including the tidal current [ 10 , 11 ], residual current [ 12 , 13 , 14 ], internal solitary waves [ 15 ], internal tides [ 16 ], tidal bores [ 17 ] and the coastal upwelling [ 18 , 19 ] et al This was attributed to its advantages, including low cost, compact system, simple instrument operation and easy execution on board. Additionally, it is worth noting that CAT reconstructs velocity structures with few sensors covering a wide range of survey zone [ 11 ], the traditional observation range (station-to-station distance), which might be less than 50 km in the coastal seas shallower than 100 m [ 2 ].…”

Section: Introductionmentioning

confidence: 99%

“…Here, the volume transport for the entire tomography domain, considered as 22 × 22 km, was calculated to be nearly equal to zero, implying that the observational errors were quite small. In 2015, an experiment using 11 CAT stations ranged between 2.4 km and 16.1 km was performed by Zhang et al [ 11 ] in the Dalian Bay where the detailed horizontal distributions of tidal and residual currents were well reconstructed with the standard inversion method. Nevertheless, the data assimilation was not to be implemented since the tomography field was not well surrounded by shorelines.…”

Section: Introductionmentioning

confidence: 99%

Mapping Small-Scale Horizontal Velocity Field in Panzhinan Waterway by Coastal Acoustic Tomography

Huang

Xie

Guo

et al. 2020

Sensors

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Mapping small-scale high-precision velocity fields is of great significance to oceanic environment research. Coastal acoustic tomography (CAT) is a frontier technology used to observe large-scale velocity field in the horizontal slice. Nonetheless, it is difficult to observe the velocity field using the CAT in small-scale areas, specifically where the flow field is complex such as ocean ranch and artificial upwelling areas. This paper conducted a sound transmission experiment using four 50 kHz CAT systems in the Panzhinan waterway. Notably, sound transmission based on the round-robin method was recommended for small-scale CAT observation. The travel time between stations, obtained by correlation of raw data, was applied to reconstruct the horizontal velocity fields using Tapered Least Square inversion. The minimum net volume transport was 8.7 m3/s at 12:32, 1.63% of the total inflow volume transport indicating that the observational errors were acceptable. The relative errors of the range-average velocity calculated by differential travel time were 1.54% (path 2) and 0.92% (path 6), respectively. Moreover, the inversion velocity root-mean-square errors (RMSEs) were 0.5163, 0.1494, 0.2103, 0.2804 and 0.2817 m/s for paths 1, 2, 3, 4 and 6, respectively. The feasibility and acceptable accuracy of the CAT method in the small-scale velocity profiling measurement were validated. Furthermore, a three-dimensional (3-D) velocity field mapping should be performed with combined analysis in horizontal and vertical slices.

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“…Coastal acoustic tomography (CAT), which was developed as a coastal‐sea application of ocean acoustic tomography (Munk et al, ), has been applied to various inland seas, estuaries, bays, and straits around Japan (Chen et al, ; Kaneko et al, ; Lin et al, ; Park & Kaneko, ; Yamaguchi et al, ; Yamaoka et al, ; Zhang et al, ; Zheng et al, ), China (Zhang et al, ; Zhu et al, ; Zhu et al, ; Zhu et al, ; Zhu et al, ), Indonesia (Syamsudin et al, ), and Taiwan (Huang et al, ). Subsurface‐moored CAT systems were deployed successfully around the underwater sound channel in the Luzon Strait in 2008 (Taniguchi et al, ).…”

Section: Introductionmentioning

confidence: 99%

Observing Internal Solitary Waves in the Lombok Strait by Coastal Acoustic Tomography

Syamsudin¹,

Taniguchi

Zhang

et al. 2019

Geophysical Research Letters

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The subsurface structures of internal solitary waves were observed over two days from 27 to 29 February 2019, by two bottom‐moored coastal acoustic tomography systems over a path length of 18.286 km in the Lombok Strait, Indonesia. One‐way travel times along the transmission path between the acoustic stations were determined for the first three arrival peaks. The resulting three travel times were used to execute a four‐layer (0–50, 150–300, 300–450, and 400–603 m) temperature inversion, constructing an underdetermined problem. The inverted four‐layer temperatures show three positive peaks and two negative peaks during the observation period, implying the sequential passage of internal solitary waves with depressed and elevated interfaces. The generation of these temperature peaks is synchronized with the diurnal tides, and the peak heights decrease with depth. The inverted four‐layer temperatures are in excellent agreement with conductivity‐temperature‐depth data obtained near the acoustic stations.

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High-precision measurement of tidal current structures using coastal acoustic tomography

Cited by 25 publications

References 15 publications

Mapping Current Fields in a Bay Using a Coast-Fitting Tomographic Inversion

Mapping Current Fields in a Bay Using a Coast-Fitting Tomographic Inversion

Mapping Small-Scale Horizontal Velocity Field in Panzhinan Waterway by Coastal Acoustic Tomography

Observing Internal Solitary Waves in the Lombok Strait by Coastal Acoustic Tomography

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