2023_programme: Estimation of three-dimensional current fields from coastal acoustic tomography system

• Session: 04. Inverse Problems in Acoustical Oceanography
  Organiser(s): Julien Bonnel and Stan Dosso
• Lecture: Estimation of three-dimensional current fields from coastal acoustic tomography system
  Paper ID: 1883
  Author(s): Hwang Yerin, Lee Eun-Joo, Park Jae-Hun
  Presenter: Park Jae-Hun
  Abstract: The Coastal acoustic tomography (CAT) system uses reciprocal acoustic signals to continuously monitor environmental changes in the coastal seas. It’s remote sensing technology makes it applicable in regions where traditional in-situ oceanic moorings with sensors are difficult to be maintained for a long time. Most of previous CAT measurements were successful in reproducing horizontal maps of the depth-averaged current and temperature fields in the coastal regions, despite the increasing demand for producing three-dimensional (3-D) fields. Here, we propose a novel method for 3-D current field estimation from CAT data using an inverse method combined with artificial neural networks. First, reciprocal acoustic travel times between five CAT stations were simulated using high resolution tide-included ocean model outputs in a region south of Korea, where in-site CAT system was established for continuous monitoring of current changes. Then, the range-averaged current profiles with five vertical layers were estimated using the artificial neural networks that were trained by the high-resolution numerical simulation results. Finally, 3-D current fields were produced by applying an inverse method at each layer. The new method was validated by comparing the estimated and simulated current fields. The validation results reveal that the new method performs well during the winter months when the baroclinicity of currents is relatively weak. During summer months, it performs reasonably by producing time-varying 2-layer-like current fields that sometimes reveal out-of-phase relationship between the upper and lower layers depending on the tidal phase. Validation simulations demonstrate that the new method is applicable enough to CAT system data because the monthly-mean root-mean-squared differences are less than 10 cm/s during summer months. Our novel method would be successfully applicable to produce continuous 3-D current fields in coastal regions without interrupting maritime traffic, fishing, and marine aquaculture activities.
• Corresponding author: Prof Jae-Hun Park
  Affiliation: Inha University
  Country: Korea
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