scholarly journals A Combined Balloon Photography and Buoy-Tracking Experiment for Mapping Surface Currents in Coastal Waters

2016 ◽  
Vol 33 (6) ◽  
pp. 1237-1250 ◽  
Author(s):  
Yasuyuki Miyao ◽  
Atsuhiko Isobe
Keyword(s):  
Field Experiments ◽  
Digital Camera ◽  
Surface Current ◽  
Marine Debris ◽  
Surface Currents ◽  
Stochastic Fluctuations ◽  
Observational Technique ◽  
The Seto Inland Sea ◽  
Ocean Surface Current ◽  
Estimated Error

AbstractA novel observational technique to map surface ocean currents at high spatial resolution in narrow regions is developed. Low-altitude remote sensing using a digital camera suspended from a vessel-towed balloon is used to track trajectories of floating buoys deployed on the ocean. Surface-current velocities are thereafter computed by sequentially moving buoy locations on photo images converted into ground (Cartesian) coordinates. Field experiments were conducted in July and August 2013 using a balloon towed by a research vessel on the Seto Inland Sea. The image-derived currents were compared with those derived from buoy locations recorded by GPS receivers attached to each floating buoy. It was found that surface currents computed using GPS data contain unrealistic values arising from stochastic fluctuations in those data. However, the image-derived currents reproduced well convergent flows and a cyclonic eddy that accumulated foam and marine debris, as actually observed during the surveys. This performance is attributed to the fact that the image processing acts as a filter to remove erroneous buoy locations in computing surface currents. The estimated error was 4.1 cm s−1, sufficiently small to measure snapshots of surface coastal currents with magnitudes greater than several tens of centimeters per second.

Modelling the trajectories of migrating Atlantic salmon (Salmo salar)

2008 ◽  
Vol 65 (3) ◽  
pp. 352-361 ◽  
Author(s):  
Douglas J Booker ◽  
Neil C Wells ◽  
I Philip Smith
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Current ◽  
Direction Finding ◽  
Surface Currents ◽  
Atlantic Salmon Salmo Salar ◽  
Ocean Surface Current ◽  
Direction Model

This paper describes a model for simulating the trajectories of migrating Atlantic salmon (Salmo salar) in the ocean. Surface current and temperature representations were used as boundary conditions for simulation of migration trajectories. Representations of surface currents were derived from a general circulation model forced by realistic winds and then tested through comparisons with observed trajectories of drifting buoys. Observed climatology data were used to represent sea surface temperature patterns. The model was used to simulate the trajectories of 15 individual salmon that were tagged in their home rivers and subsequently recaptured at sea. In contrast to a random swimming direction model, trajectories simulated using both rheotaxis and thermotaxis as direction-finding mechanisms passed close to the recapture locations of the salmon. The timings and positions of the trajectories simulated using rheotaxis corresponded more closely with the observed data than those simulated using thermotaxis. This work indicates that either rheotaxis or thermotaxis, or a combination of the two, are possible direction-finding mechanisms for migrating Atlantic salmon.

scholarly journals Velocity Estimation of Ocean Surface Currents in along-Track InSAR System Based on Conditional Generative Adversarial Networks

2021 ◽  
Vol 13 (20) ◽  
pp. 4088
Author(s):  
He Yan ◽  
Qianru Hou ◽  
Guodong Jin ◽  
Xing Xu ◽  
Gong Zhang ◽  
...  
Keyword(s):  
Current Velocity ◽  
Surface Current ◽  
Ocean Surface ◽  
Velocity Estimation ◽  
Training Dataset ◽  
Generative Adversarial Networks ◽  
Surface Currents ◽  
Ocean Surface Currents ◽  
Ocean Surface Current ◽  
Along Track

Velocity estimation of ocean surface currents is of great significance in the fields of the fishery, shipping, sewage discharge, and military affairs. Over the last decade, along-track interferometric synthetic aperture radar (along-track InSAR) has been demonstrated to be one of the important instruments for large-area and high-resolution ocean surface current velocity estimation. The calculation method of the traditional ocean surface current velocity, as influenced by the large-scale wave orbital velocity and the Bragg wave phase velocity, cannot easily separate the current velocity, characterized by large error and low efficiency. In this paper, a novel velocity estimation method of ocean surface currents is proposed based on Conditional Generative Adversarial Networks (CGANs). The main processing steps are as follows: firstly, the known ocean surface current field diagrams and their corresponding interferometric phase diagrams are constructed as the training dataset; secondly, the estimation model of the ocean surface current field is constructed based on the pix2pix algorithm and trained by the training dataset; finally, the interferometric phase diagrams in the test dataset are input into the trained model. In the simulation experiment, processing results of the proposed method are compared with those of traditional ocean surface current velocity estimation methods, which demonstrate the efficiency and effectiveness of the novel method.

scholarly journals Characteristics of surface currents in Manado Bay, North Sulawesi, Indonesia

2021 ◽  
Vol 5 (1) ◽  
pp. 42-52
Author(s):  
Aulia Dyan Yohanlis ◽  
Mutiara Rachmat Putri
Keyword(s):  
Surface Current ◽  
Current Speed ◽  
Sea Surface ◽  
Marine Debris ◽  
Surface Currents ◽  
Hydrodynamic Simulation ◽  
Average Speed ◽  
Debris Accumulation ◽  
North Sulawesi ◽  
Current Flows

Manado Bay is a complex waterway located in Manado City, North Sulawesi, Indonesia. It is an entry point for the Indonesia Trough-Flow, and its circulation is affected by the seasonal winds. Manado City has no debris net on its river estuaries. Therefore, marine debris can easily be carried away by the ocean currents and accumulate in the tourism areas located along the coast of Manado Bay. Consequently, it is important to study the sea surface current circulation in Manado Bay to deal with marine debris accumulation. In the present study, we utilized the DELFT3D software to simulate the hydrodynamic circulation in Manado Bay from 2016-2017. We conducted a 2-dimension (2D) horizontal hydrodynamic simulation using tidal and wind forcing from European Centre for Medium-Range Weather (ECMWF). The simulation results indicate that the change in bathymetry and wind affect the sea surface currents. During the summer monsoon (June-August), the sea surface current flows from the northeast to the southwest with an average speed of 1.1 cm s-1. On the contrary, during the transitional monsoon 1 (September-November), the sea surface current flows from the southeast to the northwest with an average speed of 1.3 cm s-1. Meanwhile, in the winter monsoon (December-February), the sea surface current originated from the southwest flows to the east with an average velocity of 1.9 cm s-1. Then, it moves from west to east during transitional monsoon 2 (March-May) with an average speed of 1.5 cm s-1. The current speed increases whenthe water enters the strait between the Bunaken Islands due to refraction, diffraction, and shallowing effect. As current flows toward the shallower area, the current speed increases, compensating the water column reduction.

scholarly journals Characteristic Mode Analysis of surface current distributions on metallic structures exposed to HIRF- and DCI-excitations

2020 ◽  
Vol 18 ◽  
pp. 33-41
Author(s):  
Jan Ückerseifer ◽  
Frank Gronwald
Keyword(s):  
Three Dimensional ◽  
Surface Current ◽  
Resonance Region ◽  
Mode Analysis ◽  
Surface Currents ◽  
Characteristic Mode ◽  
Metallic Structures ◽  
Current Distributions ◽  
Characteristic Modes ◽  
Physical Quantities

Abstract. This paper treats Characteristic Mode Analyses of three-dimensional test objects in the context of EMC. Based on computed Characteristic Modes and mode-specific physical quantities, series expansions for HIRF- and DCI-induced surface currents are deduced. The contribution of single Characteristic Modes to surface currents at different test frequencies is analyzed. HIRF- and DCI-excitations are compared with regard to their surface current distributions in their resonance region determined by Characteristic Mode Analysis.

Influence of coastal upwelling on the surface current in the Bay of Bengal using HF radar and satellite observations

2021 ◽  
Author(s):  
Shouvik Dey ◽  
Sourav Sil ◽  
Samiran Mandal
Keyword(s):  
Coastal Upwelling ◽  
Surface Current ◽  
Hf Radar ◽  
Second Phase ◽  
Biological Productivity ◽  
Maximum Peak ◽  
Current Observation ◽  
Ekman Layers ◽  
Ocean Surface Current ◽  
Upwelling Index

<p>Coastal Upwelling is a phenomenon in which cold and nutrient-enriched water from the Ekman layers reaches the surface enhancing the biological productivity of the upwelling region. In this work, an attempt is made to understand the influence of coastal upwelling on surface current variations during May 2018 to August 2018, when HF radar current observation (source: NIOT, India) is available. The wind-based Upwelling Index(UI<sub>wind</sub>) showed coastal upwelling throughout the study period. But the SST based upwelling index (UI<sub>sst</sub>) showed upwelling occurred only from May to the first week of June. Cross-shore components of HF radar-derived ocean surface current (CSSC)  showed strong similarity with UI<sub>sst</sub>. The first phase of upwelling from UI<sub>sst</sub> is observed to start on 5<sup>th</sup> May and lasts till 14<sup>th</sup> May with a maximum peak on around 10<sup>th</sup> May and having a horizontal extension of ~40 km. Then, there is a break period for about three days and after that, the second phase of upwelling starts on 17<sup>th</sup> May and lasts till 25<sup>th</sup> May with a maximum peak on around 20<sup>th</sup> May, but this time the horizontal extension is ~100 km which is much larger than during the first phase. A strong positive (from coast to offshore) CSSC is observed to start on around 5<sup>th</sup> May and lasts till 13<sup>th</sup> May with a maximum peak on around 10<sup>th</sup> May and having a horizontal extension of ~40 km, as observed from UIsst. A reversal of CSSC (towards coast) is noted on 14<sup>th</sup> May when the break of coastal upwelling is evident from UI<sub>sst</sub>. The CSSC then again started intensifying 15<sup>th</sup> May onwards and continued for ten days till 25<sup>th</sup> May, similar to UI<sub>sst</sub>.  The horizontal extension of the upwelling signature in the second phase of upwelling is ~70 km. Therefore, a 7-10 days of the coastal upwelling and its horizontal extension are identified in this study. This study suggests the use of high resolution (~6 km) HF radar current observation on the monitoring of coastal upwelling processes.</p>

Pneumatic and similar breakwaters

1955 ◽  
Vol 231 (1187) ◽  
pp. 457-466 ◽  
Keyword(s):  
Small Amplitude ◽  
Wave Motion ◽  
Surface Current ◽  
Water Velocity ◽  
Air Injection ◽  
Air Bubbles ◽  
Surface Currents ◽  
Damping Effect ◽  
Water Jets ◽  
Set Up

The process of calming waves by injecting air bubbles beneath the surface has been known to civil engineers for nearly 50 years. It has been little used for its results have been erratic, its method of working was unknown and its effect could not be predicted. The investigation described in this paper has shown that the surface currents set up by air injection, and the distribution of the water velocity within the currents, can be matched by currents set up by water jets, and that the two currents so matched have almost the same wave-damping effect whether they are set up by water jets or by air. It is concluded that the bubbles as such have at most a very small effect on the wave motion. It is found that waves of small amplitude are stopped in the way predicted theoretically, but that as the amplitude increases the surface current necessary to stop waves of a given length increases.

scholarly journals A New Small Drifter for Shallow Water Basins: Application to the Study of Surface Currents in the Muggia Bay (Italy)

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Carmelo Nasello ◽  
Vincenzo Armenio
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Coriolis Force ◽  
Surface Current ◽  
Meteorological Conditions ◽  
Water Current ◽  
Surface Currents ◽  
Water Basin ◽  
Surface Circulation ◽  
The City

A new small drifter prototype for measuring current immediately below the free surface in a water basin is proposed in this paper. The drifter dimensions make it useful for shallow water applications. The drifter transmits its GPS location via GSM phone network. The drifter was used to study the trajectory of the surface current in the Muggia bay, the latter containing the industrial harbor of the city of Trieste (Italy). The analysis has been carried out under a wide variety of wind conditions. As regards the behavior of the drifter, the analysis has shown that it is well suited to detect the water current since its motion is marginally affected by the wind. The study has allowed detecting the main features of the surface circulation within the Muggia bay under different meteorological conditions. Also, the study has shown that the trajectory of the surface current within the bay is weakly affected by the Coriolis force.

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