• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.9-14
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• 2007

To illusσ'ate the variation of current around artificial upwelling structure which is located in the South sea of Korea, current measurements using ADCP (Acoustic Doppler Current Profiler) during neap and spring tides were carried out on 27th July(summer)， 14th October and 30th November(Autumn), 2006. Current after the set up of artificial upwelling structure were shown different in the upper and lower layer, the boundary between the upper and lower layer was at $27{\sim}30m$ depth in summer. And the boundary layer was formed structure of three layer in Autumn. Upwelling and downwelling flow were occurred around the seamount， and these vertical flows were connected from surface to bottom The distribution of vertical shear and relative vorticity support the vertical flow around the seamount. The strength of vertical shear was higher and the direction of relative vorticity was anticlockwise (+) around the upwelling area.

• Journal of Korean Society on Water Environment
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• v.31 no.4
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• pp.367-376
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• 2015

The momentum and kinetic turbulent energy carried by the wind to a stratified lake lead to basin-scale motions, which provide a major driving force for vertical and horizontal mixing. A three-dimensional (3D) hydrodynamic model was applied to Lake Tahoe, located between California and Nevada, USA, to simulate the dominant basin-scale internal waves in the deep lake. The results demonstrated that the model well represents the temporal and vertical variations of water temperature that allows the internal waves to be energized correctly at the basin scale. Both the model and thermistor chain (TC) data identified the presence of Kelvin modes and Poincare mode internal waves. The lake was weakly stratified during the study period, and produced large amplitude (up to 60 m) of internal oscillations after several wind events and partial upwelling near the southwestern lake. The partial upwelling and followed coastal jets could be an important feature of basin-scale internal waves because they can cause re-suspension and horizontal transport of fine particles from nearshore to offshore. The internal wave dynamics can be also associated with the distributions of water quality variables such as dissolved oxygen and nutrients in the lake. Thus, the basin-scale internal waves and horizontal circulation processes need to be accurately modeled for the correct simulation of the dissolved and particulate contaminants, and biogeochemical processes in the lake.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.4
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• pp.206-211
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• 2011

Low water temperature during the summer associated with the occurrence of cold water zone off Haeundae was studied using the data from CTD observations and a monitoring buoy deployed in Suyeong Bay. Shortterm variability of current was dominant and was not related to the wind. The NE-SW components of wind parallel to the coast contained more than 96% of total variance and could account for major fluctuations of water temperature. Upwelling-response of water temperature was very sensitive so that the temperature began to decrease immediately after the onset of the southwesterly wind. In particular, there were three cases in which SW winds for only two days caused considerable temperature drops. In 2009, four upwelling events shorter than 5 days took place while seven events with periods of 2~18 days were recorded in 2010. During a very intense upwelling for seven days in mid-August 2010, temperature decreased by more than $10^{\circ}C$ in spite of the variable winds. Temperature variability at Gampo, Ulsan, Gijang and Haeundae had similar patterns. CTD observation and satellite imagery showed that the upwelling zone could be extended to the Haeundae-Busan area. According to the wavelet analysis, coherent periods were 2~8 days during the frequent upwelling/downwelling events.

• Ocean and Polar Research
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• v.24 no.2
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• pp.135-146
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• 2002

The upper ocean in the western equatorial Pacific warm pool during TOGA-COARE IMET IOP was simulated using a one-dimensional turbulence closure ocean mixed-layer model, which considered recent observations, such as the remarkable enhancement of turbulent kinetic energy near the ocean surface. The shoaling/deepening of the mixed layer and warming/cooling subsurface water in the model were in reasonable agreement with the observations. There was a significant improvement in simulating the cooling trend of the sea surface temperature under a westerly wind burst with heavy rainfall over previous simulations using bulk mixed-layer models. By contrast the simulated sea surface salinity (SSS) departed significantly from the observed SSS, especially during a westerly burst and the subsequent restratification period, which might be due to 3-D control processes, such as downwelling/upwelling or advection.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.4 s.27
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• pp.301-306
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• 2006

In order to estimate the characteristics of water movements around artificial upwelling structure, current measurements were carried out along lines E-W and S-N on May 4th(neap tide} and May 30th(spring tide), 2006. In the study area, southeastward flow was dominant during the field observations, and the pattern of water movement in the upper layer above 30m depth was different from that in the lower layer below 30m depth Vertical flow(w-component} around the artificial structure area and western area was shown to be upward flow, but downward flow occurred in the southern, northern and eastern parts at the neap tide. At the spring tide, the ebb current along E-W line showed upwelling flow in the eastern part and western area and showed upwelling flow near the artificial structure area and downwelling flow far away that one. At the spring tide, upward flow was dominant along S-N line during the flood current Volume transport by upward flow was higher than that by downward flow. Volume transport by upward flow during ebb of neap tide was greater than during flood current of neap tide, but was reverse at the spring tide.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.53-63
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• 1998

The Princeton ocean model (POM) with free surface in sigma-coordinate, governed by primitive equations, is used to examine the response of sea water in Deukryang Bay to a typhoon. The model reproduces reasonably well the main features in the wind-driven dynamics due to passing of a typhoon. In response to the wind, the coastal jet develops and the upwelling(or downwelling) occurs dominantly in both sides of the bay. This result implies that there should be an overturn in the bay water with the passing of typhoons. Numerical results of POM are also compared to those of a depth-averaged model. From the comparison, it is postulated that the bottom drag coefficient conventionally used for the two-dimensional flow models is inadequate due to overestimation of the computed current field.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.508-520
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• 2016

In this study, variations in water temperature after the passage of typhoons in Korean waters from 2009-2015 were analyzed. Sea surface temperature (SST) images derived from satellite remote sensing data were used, and water temperature information came from real-time mooring buoys at Yangyang, Gangneung, Samcheok and Yeoungdeok, while wind data was supplied by the Korea Meteorological Administration. Differences in SST observed before and after the passage of a typhoon using the SST images were found to be affected by wind direction as well as hot and cool seasonal tendencies. Coastal water temperatures of the eastern part of the Korean peninsula, located to the right of a typhoon, as in the case of typhoons Muifa, Chanhom, Nakri and Tembin, were lowered by a coastal upwelling system from southerly winds across the water's surface at depths of 15m and 25m. In particular, typhoons Chanhom and Tembin decreased water temperatures by about $8-11^{\circ}C$ and $16^{\circ}C$, respectively. However, temperatures to the left of the typhoons were increased by a downwelling of offshore seawater with a high temperature through the mid and lower seawater layers. After the passage of the typhoons, further mixing of seawater at a higher or lower temperature due to southerly or northerly winds, according to the context, lasted for 1-2 or 4 days, respectively.

• Journal of Wetlands Research
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• v.11 no.1
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• pp.123-130
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• 2009

Hyporheic zone is an area where hydraulic exchanges occur between surface water and ground water. Such transient area is anticipated to facilitate diverse biogeochemical reactions by providing habitats for various microorganism. However, only a few data are available about microbial properties in hyporheic zone, which would be important in better understanding of biogeochemical reactions in whole streams. The study site is Naesung stream, located in the north Kyoung-Sang Province, of which sediment is sandy with little anthropogenic impacts. Soil samples were collected from a transect placed perpendicular to stream flow. The transect includes upland fringe area dominated by Phragmites japonica, bare soil, and soil adjacent to water. In addition, soil samples were also collected from downwelling and upwelling areas in hyporheic zone within the main channel. Soils were collected from 3 depth in each area, and water content, pH, and DOC were measured. Various microbial properties including extracellular enzyme activities ($\beta$-glucosidase, N-acetylglucosaminidase, phosphatase and arylsulfatase), and microbial community structure using T-RFLP were also determined. The results exhibited a positive correlation between water content and DOC, and between extracellular enzyme activities and DOC. Distinctive patterns were observed in soils adjacent to water and hyporheic zone compared with other soils. Overall results of study provided basic information about microbial properties of hyporheic zone, which appeared to be discernable from other locations in the stream corridor.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.53-53
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• 2015

Basin-scale motions in a stratified lake rely on interactions of spatially and temporally varying wind force, bathymetry, density variation, and earth's rotation. These motions provide a major driving force for vertical and horizontal mixing of inorganic and organic materials, dissolved oxygen, storm water and floating debris in stratified lakes. In Lake Tahoe, located between California and Nevada, USA, basin-scale circulations are obviously important because they are directly associated with the fate of the suspended particulate materials that degrade the clarity of the lake. A three-dimensional hydrodynamic model, ELCOM, was applied to Lake Tahoe to investigate the underlying mechanisms that determine the characteristics of basin-scale circulations. Numerical experiments were designed to examine the relative effects of various mechanisms responsible for the horizontal circulations for two different seasons, summer and winter. The unique double gyre, a cyclonic northern gyre and an anti-cyclonic southern gyre, occurred during the winter cooling season when wind stress curl, stratification, and Coriolis effect were all incorporated. The horizontal structure of the upwelling and downwelling formed due to basin-scale internal waves found to be closely related to the rotating direction of each gyre. In the summer, the spatially varying wind field and the Coriolis effect caused a dominant anti-cyclonic gyre to develop in the center of the lake. In the winter, a significant wind event excited internal waves, and a persistent (2 week long) cyclonic gyre formed near the upwelling zone. Mechanism of the persistent cyclonic gyre is explained as a geostrophic circulation ensued by balancing of the baroclinc pressure gradient (or baroclinic instability) and Coriolis effect. Topographic effect, examined by simulating a flat bathymetry with constant depth of 300m, was found to be significant during the winter cooling season but not as significant as the wind curl and baroclinic effects.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2744-2749
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• 2008

Numerical calculations are carried out for the natural convection induced by temperature difference between a cold outer square cylinder and a hot inner circular cylinder for Rayleigh number of $Ra=10^7$. This study investigates the effect of the inner cylinder location on the heat transfer and fluid flow. The location of inner circular cylinder ($\delta$) is changed vertically along the center-line of square enclosure. The natural convection bifurcates from unsteady to steady state according to $\delta$. Two critical positions of ${\delta}_{C,L}$ and ${\delta}_{C,U}$ as a lower bound and an upper bound are ${\delta}_{C,L}=0.05$ and ${\delta}_{C,U}=0.18$, respectively. Within the defined bounds, the thermal and flow fields are steady state. When the inner cylinder locates at ${\delta}{\geq}{\delta}_{C,U}$, the space between the upper surface of inner cylinder and the top surface of the enclosure forms a relatively shallow layer where the natural convection characterized as the pure Rayleigh-Benard convection forms alternately the upwelling and downwelling plums, as a result that a series of cells known as Benard cells is derived.