• Ocean and Polar Research
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• v.26 no.3
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• pp.453-463
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• 2004

The Antarctic Peninsula is important in terms of global warming research due to pronounced increase of air temperature over the last century. The first eddy covariance system was established at King Sejong Station located in the northern region of the Antarctic Peninsula in December of 2002 and has been operated over one year. Here, we analyze turbulent characteristics to determine quality control criteria for turbulent sensible heat flux data as well as to diagnose the possibility of long term eddy covariance measurement under extreme weather conditions of the Antarctic Peninsula. We also report the preliminary result on sensible heat flux. Based on the analyses on turbulent characteristics such as integral turbulence characteristics of vertical velocity (w) and heat (T), stationarity test and investigation of correlation coefficient, they fallow the Monin-Obukhov similarity and eddy covariance flux data were reliable. ${\sim}47%$ of total retrieved sensible heat flux data could be used for further analysis. Daytime averaged sensible heat flux showed a pronounced seasonal variation, with a maximum of up to $300Wm^{-2}$ in summer. In conclusion, continuous and long-term eddy covariance measurement may be possible at the study site and the land surface may influence the atmosphere significantly through heat transport in summer.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2009.10a
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• pp.65-68
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• 2009

• Wind and Structures
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• v.14 no.5
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• pp.465-480
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• 2011

In this paper, a stabilized large eddy simulation technique is developed to predict turbulent flow with high Reynolds number. Streamline Upwind Petrov-Galerkin (SUPG) stabilized method and three-step technique are both implemented for the finite element formulation of Smagorinsky sub-grid scale (SGS) model. Temporal discretization is performed using three-step technique with viscous term treated implicitly. And the pressure is computed from Poisson equation derived from the incompressible condition. Then two numerical examples of turbulent flow with high Reynolds number are discussed. One is lid driven flow at Re = $10^5$ in a triangular cavity, the other is turbulent flow past a square cylinder at Re = 22000. Results show that the present technique can effectively suppress the instabilities of turbulent flow caused by traditional FEM and well predict the unsteady flow even with coarse mesh.

• Ocean and Polar Research
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• v.27 no.2
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• pp.231-235
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• 2005

The European Iron Fertilization Experiment EIFEX studied the growth and decline of a phytoplankton bloom stimulated by fertilising $10km^2$ in the core of a mesoscale $(80{\times}120km)$ cyclonic eddy south of the Antarctic Polar Front with about 2 times 7 tonnes of iron sulphate. The phytoplankton accumulation induced by iron fertilization did not exceed $3{\mu}g\;chl\;a\;l^{-1}$ despite a draw down of $5{\mu}M$ of nitrate that should have resulted in at least double to triple the amount of phytoplankton biomass assuming regular Redfield-ratios for draw down after phytoplankton growth in the Southern Ocean. During EIFEX the fertilized core of the mesoscale eddy evolved to a hotspot for a variety of small and medium sized mesozooplankton copepods. In contrast to copepods, the biomass of salps (Salpa thompson)) that dominated zooplankton biomass before the onset of our experiment decreased to nearly extinction. Most of the species of the rnosozooplankton community showed extremely hiか feeding rates compared to literature values from Southern Ocean summer communities. At the end of the experiment, massive phytoplankton sedimentation reached the sea floor at about 3800m water depth.

• Ocean and Polar Research
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• v.24 no.4
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• pp.369-389
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• 2002

CTD data taken in the Ulleung Basin between 1996 and 2001 are analyzed to understand the hydrography around Dokdo. Major features occurring in the Ulleung Basin such as the path variability of the East Korean Warm Current (EKWC), the location and size of the Ulleung Warm Eddy (UWE) and the position of the Offshore Branch along the Japanese coast all influence the hydrography around Dokdo. The Dokdo area frequently lies in the eastern part of the meandering EKWC and the UWE that results in a filting of isolines sloping upwards to Dokdo in the Ulleung Interplain Gap (UIG) between Ulleungdo and Dokdo. Subsurface water near Dokdo then becomes colder and less saline than water near Ulleungdo. Two cases that are opposite to this general trend are also identified when the Dokdo area is directly affected by the EKWC and by a small scale eddy ffd by the Offshore Branch. High salinity cores and warm waters are then found near Dokdo with isolines sloping upwards to Ulleungdo. Freshening of the East Sea Intermediate Water was observed in the UIG when neither the EKWC nor the UWE was developed in the Ulleung Basin during June-November 2000.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.49-55
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• 2003

When a body with slant angle after its shoulder is moving at high speed, the turbulent motion around the afterbody is generally associated with the flaw separation and determines the normal component of the drag. By changing the slant angle of afterbody, there exists a critical angle at which the drag coefficients change drastically. Understanding and control of the turbulent separated flows are of significant importance for the design of optimal configuration of the moving bodies. In the present paper, a new Large Eddy Simulation technique has been developed to investigate turbulent vortical motions around the afterbodies with slant angle. By basis of understanding the structure of turbulent flaw around the body, the new configuration of afterbodies are designed to reduce the drag of body and the nonlinear effects due to the interaction between the body configuration and the turbulent separated flows are investigated by use of the developed LES technique.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.351-373
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• 2019

The cold eddies around the Ulleung Basin in the East Sea were identified from satellite altimeter sea level data using the Winding-Angle method from 1993 to 2015. Among the cold eddies, the Dokdo Cold Eddies (DCEs), which were formed at the first meandering trough of the East Korea Warm Current (EKWC) and were pinched off to the southwest from the eastward flow, were classified and their migration patterns were analyzed. The vertical structures of water temperature, salinity, and flow velocity near the DCE center were also examined using numerical simulation and observation data provided by the Hybrid Coordinate Ocean Model and the National Institute of Fisheries Science, respectively. A total of 112 DCEs were generated for 23 years. Of these, 39 DCEs migrated westward and arrived off the east coast of Korea. The average travel distance was 250.9 km, the average lifespan was 93 days, and the average travel speed was 3.5 cm/s. The other 73 DCEs had moved to the east or had hovered around the generated location until they disappeared. At 50-100 m depth under the DCE, water temperature and salinity (T < $5^{\circ}C$, S < 34.1) were lower than those of ambient water and isotherms made a dome shape. Current faster than 10 cm/s circulates counterclockwise from the surface to 300 m depth at 38 km away from the center of DCE. After the EKWC separates from the coast, it flows eastward and starts to meander near Ulleungdo. The first trough of the meander in the east of Ulleungdo is pushed deep into the southwest and forms a cold eddy (DCE), which is shed from the meander in the south of Ulleungdo. While a DCE moves westward, it circumvents the Ulleung Warm Eddy (UWE) clockwise and follows U shape path toward the east coast of Korea. When the DCE arrives near the coast, the EKWC separates from the coast at the south of DCE and circumvents the DCE. As the DCE near the coast weakens and extinguishes about 30 days later after the arrival, the EKWC flows northward along the coast recovering its original path. The DCE steadily transports heat and salt from the north to the south, which helps to form a cold water region in the southwest of the Ulleung Basin and brings positive vorticity to change the separation latitude and path of the EKWC. Some of the DCEs moving to the west were merged into a coastal cold eddy to form a wide cold water region in the west of Ulleung Basin and to create a elongated anticlockwise circulation, which separated the UWE in the north from the EKWC in the south.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.455-462
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• 2015

It is well known that warm eddy is frequently developed through the year in the East Sea. The warm eddy may affect sound propagation due to changes of sound velocity structures in the sea water. To verify the effects of the warm eddy for long-range sound propagation, transmission loss and performance surface, which were used mean direct signal excess range generated by sound propagation modeling using re-analyzed climatology data on March 23th in 2007 were analysed. From these analyses, we found that characteristics of sound propagation in the sea water are changed by the warm eddy, and boundaries of the warm eddy act as a barrier for long-range sound propagation. Furthermore, these disadvantages of the eddy related to sound propagation were increased when the sea bottom depth is shallow.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.354-363
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• 1995

Temporal change of a warm eddy off Sogcho was studied using satellite infrared images from January to lune 1992 and its structure was investigated by the observations in Hay. There were two kinds of event for eddy formation. IR images in January indicated that the eddy Haying a horizontal dimension of about 200km was first formed by an injection of warm water. After some deformation and cooling processes the second restrengthening event took place in late March when a warm filament began to penetrate northward and circumvented the preexisting eddy. This eddy became a complete ring-shape with cooled water arrested inside from April to May. The maximum thickness of the isothermal subsurface layer with temperature of $10.0-10.4^{\circ}C$ was about 170m. Except that the current velocity was about 80cm/sec near the axis of the last Korea Warm Current close to Sogcho, the interior of the eddy had an anticyclonic motion with overall swirl velocity of 30-50cm/sec. Velocity rapidly decreased vertically below the main thermocline.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.13 no.1
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• pp.1-5
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• 1977

A series of echo-sounding and current measurements as well as the drogue and the drift bottle experiments were carried out in Asan Bay since November 1974. Several sand bars or sand flats covered by silts were developed at ebb tide in the bay. Sand waves and sand ripples were seen on the surface of the sand bars, around which sea channels of 8~ 12 meters in depth are formed. The main stream axis of the flood current which is separated into east and west branch flows southward. A cyclonic and an anticyclonic eddy are developed at the early stage of flood tide. They are transformed into a clockwise eddy before the slack water. The maximum tidal current speed observed was 3.1 ~ 3.2 knots at the entrance of the bay, while it was 1.O ~ 2.8 knots in the bay. The location of the main stream axis of the tidal current coincides well with the sea channel. A salt wedge was observed at the estuary of the Sabgyo-cheon River.