Tomographic measurements of the Kuroshio Extension Meander and its associated eddies

Yuan, Gang; Nakano, Iwao; Fujimori, Hidetoshi; Nakamura, Toshiaki; Kamoshida, Takashi; Kaya, A.

doi:10.1029/1998gl900253

Cited by 21 publications

(11 citation statements)

References 4 publications

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“…The values of physical parameters uncontrolled by the assimilation scheme were chosen to resemble conditions in the Kuroshio Extension region, where an AT array of five acoustic transceivers was deployed and maintained for 2 months in 1997 (Yuan et al 1999). The background distributions of the Brunt-Väisäla frequency and the reciprocal sound speed velocity b for that region are shown in Fig.…”

Section: A the Modelmentioning

confidence: 99%

“…Owing to relative paucity of AT observations in the ocean, much less attention has been paid to their processing by the tools involving both statistical and dynamical constraints. Most of the AT data inversions present in literature are done by 3D statistical methods (Howe et al 1987;Yuan et al 1999). Applications of dynamics to the inversion of the AT data are rather sparse and scanty.…”

Section: Introductionmentioning

confidence: 99%

“…This is done to avoid uncertainties associated with the poorly known statistics of the background control fields, especially of those at the open lateral boundaries. In formulating twin data experiments (selecting AT transceivers' positions, altimeter tracks, oceanic stratification, and bottom topography) we tried to be as close as possible to the baseline observational network and oceanic parameters of the 2-month medium-range tomography experiment in the Kuroshio Extension region (Yuan et al 1999).…”

Section: Introductionmentioning

confidence: 99%

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Simulations of Quasigeostrophic Currents Derived from Satellite Altimetry and Acoustic Tomography of an Open Ocean Region*

Yaremchuk

Nechaev

2001

J. Atmos. Oceanic Technol.

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Acoustic tomography (AT) and satellite altimetry (SA) measure properties of the ocean state with high temporal resolution. That makes these data suitable for long-term monitoring of mesoscale features in the open ocean regions, where the open boundaries are the major sources of model forecast uncertainties on timescales larger than 1 week. In this paper, a finite-difference quasigeostrophic model of an open ocean region is considered as a possible tool for interpolating AT-SA data in space and time. The assimilation algorithm is based upon the 4D variational data assimilation scheme controlled by the initial and boundary conditions of the model. The model configuration used in the simulations corresponds to the AT array deployed by the Japan Marine Science and Technology Center (JAMSTEC) in the region of the Kuroshio Extension in 1997. Twin data experiments show that mesoscale features in an area of 1000 km ϫ 1000 km can be effectively monitored by five acoustic transceivers, measuring reciprocal travel times. The quality of assimilation is studied as a function of the position of the transceivers in the vertical and the effective number of monitored rays. It is shown that reciprocal travel time observations (differential tomography) in combination with SA provide a significant improvement of the quality of assimilation. * IPRC/SOEST Contribution Number 92/5561.

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Section: A the Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulations of Quasigeostrophic Currents Derived from Satellite Altimetry and Acoustic Tomography of an Open Ocean Region*

Yaremchuk

Nechaev

2001

J. Atmos. Oceanic Technol.

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“…Ocean acoustic tomography (OAT) is a powerful tool that can estimate the structure of sound speed (mainly proportional to temperature) and current in the ocean (Munk et al, 1995). Other than coastal sea studies (e.g., Park and Kaneko, 2000), most previous experiments have been carried out in the deep ocean, characterized with a full structure of the underwater sound channel (Cornuelle et al, 1985;Cornuelle et al, 1993;Dushaw et al, 1995;Dushaw et al, 1994;Howe et al, 1987;Send et al, 1995;Worcester et al, 1985;Yuan et al, 1999). However, its application to shallower regions with a sound speed profile (SSP) decreasing toward the bottom from the surface was limited because of the difficulty of ray resolvability (DeFerrari and Nguyen, 1986).…”

Section: Introductionmentioning

confidence: 99%

Measuring the Kuroshio Current with ocean acoustic tomography

Taniguchi

Huang

Kaneko

et al. 2013

The Journal of the Acoustical Society of America

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Ocean current profiling using ocean acoustic tomography (OAT) was conducted in the Kuroshio Current southeast of Taiwan from August 20 to September 15, 2009. Sound pulses were transmitted reciprocally between two acoustic stations placed near the underwater sound channel axis and separated by 48 km. Based on the result of ray simulation, the received signals are divided into multiple ray groups because it is difficult to resolve the ray arrivals for individual rays. The average differential travel times from these ray groups are used to reconstruct the vertical profiles of currents. The currents are estimated with respect to the deepest water layer via two methods: An explicit solution and an inversion with regularization. The strong currents were confined to the upper 200 m and rapidly weakened toward 500 m in depth. Both methods give similar results and are consistent with shipboard acoustic Doppler current profiler results in the upper 150 m. The observed temporal variation demonstrates a similar trend to the prediction from the Hybrid Coordinate Ocean Model.

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“…Experiments conducted so far have shown that tomography is a powerful tool to integrate in situ and satellite observations for long term monitoring over wide areas (Yaremchuk & Nechaev 2001). It has been successfully applied to the study of seasonal thermocline displacement (Skarsoulis & Send 2000), dense water formation (Send et al 1995, Lab Sea Group 1998, Kindler et al 2001, El Niño (Shang & Wang 1994), and meander and eddy structure (Yuan et al 1999). It is especially useful for monitoring oceanic ice covered areas as it can provide information for the upper layer, where direct measurements are not feasible.…”

Section: Introductionmentioning

confidence: 99%

Monitoring polynyas with Ocean Acoustic Tomography: a feasibility study in Terra Nova Bay

Marinis

Picco

Meloni³

2003

Antartic science

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Abstract:This study looks at the feasibility of using Ocean Acoustic Tomography for long-term monitoring of polynyas using both observations in Terra Nova Bay polynya (Ross Sea) and simulations with a range dependent, multi-layered adiabatic normal mode acoustic propagation model. The summer sound speed profile is characterized by surface values of around 1450 m s slope. Thus, the sound propagation is apparently ducted in the near surface layer and is refracted upward below it. During winter, due to water cooling and mixing processes, the subsurface minimum disappears, the surface sound speed is about 1440 m s -1 and no near surface layer ducted propagation occurs. Because of the specificity of the Terra Nova Bay seasonal sound speed profile and to cope with both deep and shelf water applicability, the feasibility study of acoustic inversion was undertaken using normal mode Match Field Tomography instead of the more classical travel-time inversion.The results from simulations demonstrate that ocean acoustic tomography is able to reproduce quite well the vertical sound speed profile, in particular the temporal evolution of summer stratification and winter mixing processes, thus providing information on the upper layer, where direct measurements are not possible.

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Tomographic measurements of the Kuroshio Extension Meander and its associated eddies

Cited by 21 publications

References 4 publications

Simulations of Quasigeostrophic Currents Derived from Satellite Altimetry and Acoustic Tomography of an Open Ocean Region*

Simulations of Quasigeostrophic Currents Derived from Satellite Altimetry and Acoustic Tomography of an Open Ocean Region*

Measuring the Kuroshio Current with ocean acoustic tomography

Monitoring polynyas with Ocean Acoustic Tomography: a feasibility study in Terra Nova Bay

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