Use of Global Satellite Altimeter and Drifter Data for Ocean Current Resource Characterization

2017 ◽  
pp. 159-177 ◽  
Author(s):  
Ruo-Shan Tseng ◽  
Yu-Chia Chang ◽  
Peter C. Chu
Keyword(s):  
Ocean Current ◽  
Satellite Altimeter ◽  
Current Resource

scholarly journals Analysis of Upwelling Events in the Southern South China Sea Using Multi-Mission Satellite Altimeter

2021 ◽  
Vol 16 ◽  
pp. 1-15
Author(s):  
Ami Hassan Md Din ◽  
Abdul Rafiq Dolhan ◽  
Mohammad Hanif Hamden ◽  
Mat Nizam Uti ◽  
Muhammad Faiz Pa’suya
Keyword(s):  
South China Sea ◽  
South China ◽  
Tide Gauge ◽  
Ocean Current ◽  
Observation System ◽  
In Situ Observation ◽  
Limited Information ◽  
Satellite Altimeter ◽  
China Sea ◽  
Mission Satellite

Upwelling is a vital ocean behaviour, especially for the Fisheries Industry, where upwelling will help to detect fish ground at a particular ocean area. However, the study of upwelling is minimal and not well understood due to some reasons and constraints, such as limited observation. Upwelling lacks a comprehensive in-situ observation system where it relies on limited information collected from the ground-truthing execution such as ships, buoys, and current meter.  This study aims to analyse the upwelling pattern in the southern region of the South China Sea by using a multi-mission satellite altimeter. In order to derive the physical oceanography that involves upwelling, such as sea surface height (SSH), Mean Dynamic Topography (MDT), and the Sea Level Anomaly (SLA), the Radar Altimeter Database System is used. Five Satellite Altimeter mission is used in this study, which is JASON-2, JASON-3, CYROSAT2, SARAL, SENTINAL3A from 2013 to 2017. Validation is made using a statistical method showing a good correlation between Altimetry data and Tidal Data at tide gauge, which is 0.84 to 0.97, respectively. Also, monthly altimetry derived Geostrophic Current was assessed by analysing the current pattern where it shows a similarity with a previous study where the current velocity is 0.5ms-1 to 2ms-1. From the result, eddies can be seen in the seasonal and monthly Absolute Geostrophic Ocean Current (AGOC) map, indicating the present presence of upwelling. In conclusion, this study will benefit other researchers in terms of both upwelling and eddy studies. 

scholarly journals Structure and variability of the synoptic disturbances of ocean currents in the Drake Passage and Scotia Sea

2019 ◽  
Vol 59 (2) ◽  
pp. 191-200
Author(s):  
M. N. Koshlyakov ◽  
I. A. Repina ◽  
D. S. Savchenko ◽  
R. Yu. Tarakanov ◽  
V. K. Taroyan
Keyword(s):  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Statistical Characteristics ◽  
Ocean Current ◽  
Satellite Altimeter ◽  
Scotia Sea ◽  
Circumpolar Current ◽  
High Degree ◽  
Set Of Points ◽  
Absolute Dynamics

Twenty two years data of the satellite altimeter observations are used for the analysis of structure and variability of the ocean current synoptic disturbances in the Drake Passage and Scotia Sea. Wavelet analysis of the time series of ocean surface absolute dynamics topography (OSADT) at a set of points in the studied ocean area has revealed a high degree of the statistical nonstationarity of these series appearing as short (few years) intervals of intensive fluctuations of OSADT separated by long intervals of weak fluctuations. Analysis of the synoptic OSADT maps has showed that the intervals of the strong ocean current fluctuations at a point are conditioned by the alternation of processes of cyclonic and anticyclonic eddy-meanders formation by the jets of Antarctic Circumpolar Current, strengthening of the eddies, their following attenuation and final eddy confluence with the mother jets. Besides of the statistical nonstationarity, a considerable spatial variability of the statistical characteristics of the ocean current synoptical disturbances has been revealed for the scales of 150–200 km.

Satellite Altimeter Results Over East Antarctica

1982 ◽  
Vol 3 ◽  
pp. 32-35 ◽  
Author(s):  
R. L. Brooks
Keyword(s):  
Tracking System ◽  
Ice Sheet ◽  
East Antarctica ◽  
Satellite Altimeter ◽  
Ice Shelves ◽  
Ice Surface ◽  
Operational Lifetime ◽  
Waveform Retracking ◽  
Better Than

During the operational lifetime of the Seasat altimeter from 3 July to 10 October 1978, more than 450 overflights were made over East Antarctica inland to latitude 72°S. An analysis of selected passes over a variety of ice features demonstrates that the oceanographic altimeter performed surprisingly well over the ice sheet and ice shelves, acquiring useful measurements during approximately 70% of each pass. The altimeter's onboard tracking system dampened out the ice-surface elevations, but post-flight retracking of the stored return waveforms reveals excellent ice-surface details. After waveform retracking, the altimeter repeatability is better than ±1 m.

A Feasibility Demonstration of Ocean Model Eddy-resolving Nowcast/Forecast Skill Using Satellite Altimeter Data

2000 ◽  
Author(s):  
Harley E. Hurlburt ◽  
Robert C. Rhodes ◽  
Charlie N. Barron ◽  
E. J. Metzger ◽  
Ole M. Smedstad
Keyword(s):  
Ocean Model ◽  
Forecast Skill ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Satellite Altimeter Data

scholarly journals Robust Position Control of an Over-actuated Underwater Vehicle under Model Uncertainties and Ocean Current Effects Using Dynamic Sliding Mode Surface and Optimal Allocation Control

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 747
Author(s):  
Mai The Vu ◽  
Tat-Hien Le ◽  
Ha Le Nhu Ngoc Thanh ◽  
Tuan-Tu Huynh ◽  
Mien Van ◽  
...  
Keyword(s):  
Control System ◽  
Motion Control ◽  
Optimal Allocation ◽  
Position Control ◽  
Sliding Mode ◽  
Underwater Vehicle ◽  
Ocean Current ◽  
Model Uncertainties ◽  
Control Module ◽  
Dynamic Sliding Mode

Underwater vehicles (UVs) are subjected to various environmental disturbances due to ocean currents, propulsion systems, and un-modeled disturbances. In practice, it is very challenging to design a control system to maintain UVs stayed at the desired static position permanently under these conditions. Therefore, in this study, a nonlinear dynamics and robust positioning control of the over-actuated autonomous underwater vehicle (AUV) under the effects of ocean current and model uncertainties are presented. First, a motion equation of the over-actuated AUV under the effects of ocean current disturbances is established, and a trajectory generation of the over-actuated AUV heading angle is constructed based on the line of sight (LOS) algorithm. Second, a dynamic positioning (DP) control system based on motion control and an allocation control is proposed. For this, motion control of the over-actuated AUV based on the dynamic sliding mode control (DSMC) theory is adopted to improve the system robustness under the effects of the ocean current and model uncertainties. In addition, the stability of the system is proved based on Lyapunov criteria. Then, using the generalized forces generated from the motion control module, two different methods for optimal allocation control module: the least square (LS) method and quadratic programming (QP) method are developed to distribute a proper thrust to each thruster of the over-actuated AUV. Simulation studies are conducted to examine the effectiveness and robustness of the proposed DP controller. The results show that the proposed DP controller using the QP algorithm provides higher stability with smaller steady-state error and stronger robustness.

scholarly journals Interannual to decadal variability of phosphate in the Oyashio region: Roles of wind-driven ocean current and tidally induced vertical mixing in the Sea of Okhotsk

2021 ◽  
pp. 102615
Author(s):  
Takuya Nakanowatari ◽  
Tomohiro Nakamura ◽  
Humio Mitsudera ◽  
Jun Nishioka ◽  
Hiroshi Kuroda ◽  
...  
Keyword(s):  
Sea Of Okhotsk ◽  
Decadal Variability ◽  
Vertical Mixing ◽  
Ocean Current ◽  
Oyashio Region ◽  
The Sea Of Okhotsk

Modeling, simulation, and equilibrium analysis of tethered coaxial dual-rotor ocean current turbines

2021 ◽  
Vol 243 ◽  
pp. 113929
Author(s):  
Rodney Metoyer ◽  
Punnag Chatterjee ◽  
Kelsey Elfering ◽  
Matthew Bryant ◽  
Kenneth Granlund ◽  
...  
Keyword(s):  
Equilibrium Analysis ◽  
Ocean Current ◽  
Modeling Simulation

scholarly journals Numerical Study of an Oscillating-Wing Wingmill for Ocean Current Energy Harvesting: Fluid-Solid-Body Interaction with Feedback Control

2020 ◽  
Vol 9 (1) ◽  
pp. 23
Author(s):  
David Balam-Tamayo ◽  
Carlos Málaga ◽  
Bernardo Figueroa-Espinoza
Keyword(s):  
Energy Harvesting ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Ocean Current ◽  
Control Synthesis ◽  
Dimensionless Number ◽  
Control Law ◽  
Loop Control ◽  
Power Extraction ◽  
Current Energy

The performance and flow around an oscillating foil device for current energy extraction (a wingmill) was studied through numerical simulations. OpenFOAM was used in order to study the two-dimensional (2D) flow around a wingmill. A closed loop control law was coded in order to follow a reference angle of attack. The objective of this control law is to modify the angle of attack in order to enhance the lift force (and increase power extraction). Dimensional analysis suggests a compromise between the generator (or damper) stiffness and actuator/control gains, so a parametric study was carried out while using a new dimensionless number, called B, which represents this compromise. It was found that there is a maximum on the efficiency curve in terms of the aforementioned dimensionless parameter. The lessons that are learned from this fluid-structure and feedback coupling are discussed; this interaction, combined with the feedback dynamics, may trigger dynamic stall, thus decreasing the performance. Moreover, if the control strategy is not carefully selected, then the energy spent on the actuator may affect efficiency considerably. This type of simulation could allow for the system identification, control synthesis, and optimization of energy harvesting devices in future studies.

Disturbance learning controller design for unmanned surface vehicle using LSTM technique of recurrent neural network

2021 ◽  
pp. 1-11
Author(s):  
Sang-Ki Jeong ◽  
Dea-Hyeong Ji ◽  
Ji-Youn Oh ◽  
Jung-Min Seo ◽  
Hyeung-Sik Choi
Keyword(s):  
Neural Network ◽  
Control System ◽  
Flow Velocity ◽  
Recurrent Neural Network ◽  
Pid Controller ◽  
Short Term Memory ◽  
Ocean Currents ◽  
Ocean Current ◽  
Movement Speed ◽  
Marine Research

In this study, to effectively control small unmanned surface vehicles (USVs) for marine research, characteristics of ocean current were learned using the long short-term memory (LSTM) model algorithm of a recurrent neural network (RNN), and ocean currents were predicted. Using the results, a study on the control of USVs was conducted. A control system model of a small USV equipped with two rear thrusters and a front thruster arranged horizontally was designed. The system was also designed to determine the output of the controller by predicting the speed of the following currents and utilizing this data as a system disturbance by learning data from ocean currents using the LSTM algorithm of a RNN. To measure ocean currents on the sea when a small USV moves, the speed and direction of the ship’s movement were measured using speed, azimuth, and location (latitude and longitude) data from GPS. In addition, the movement speed of the fluid with flow velocity is measured using the installed flow velocity measurement sensor. Additionally, a control system was designed to control the movement of the USV using an artificial neural network-PID (ANN-PID) controller [12]. The ANN-PID controller can manage disturbances by adjusting the control gain. Based on these studies, the control results were analyzed, and the control algorithm was verified through a simulation of the applied control system [8, 9].

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