• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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• pp.286-295
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• 2016

With the results of observations in 2013 and 2014 including ocean buoys, in-situ investigations and wind data, we examined the spatio-temporal variation of cold water masses along the eastern coast of Korea. Usually, a cold water mass first appears along the northern part of the eastern coast from May to July, and then along the southern part of the eastern coast from late June to mid-August. Cold water masses appear 3~5 times a year and remain for 5~20 days in the southwestern part of the East Sea. A distinctive cold water mass appeared usually in mid-July in this area, the surface temperature of which was below $10^{\circ}C$ in some cases. During the appearance of a cold water mass in the southwestern part of the East Sea, the horizontal temperature gradient was large at the surface and a significant low water temperature below $8^{\circ}C$ appeared at the bottom level. This appearance of cold water masses clearly corresponded to southwesterly winds, which generated coastal upwelling.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.19-32
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• 2002

This study is objected to identify the relations between surface- and shallow ground-water and the seasonal variation of their qualities in watersheds near Muju area. The water type shows mainly Ca-$HCO_3$type. Heavy-metal contamination of surface water is locally detected, due to the mixing with mine drainage. In October nitrate concentration is especially high in densely populated area. Cluster Analysis and Principal Component Analysis are implemented to interpret the complexity of the chemical variation of surface- and ground-water with large amount of chemical data. Based on the cluster analysis, surface-water was divided into five groups and ground-water into three groups. Principal Component Analysis efficiently supports the result of cluster analysis, allowing the identification of three main factors controlling the water quality. There are (1) hydrogeochemical factor, (2) anthropogenic factor and (3) heavy metal contaminated by mine drainage.

• Ocean and Polar Research
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• v.33 no.spc3
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• pp.371-383
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• 2011

To investigate the physical characteristics and variations of oceanic parameters in the tropical central North Pacific, oceanographic surveys were carried out in summer of 2006 and 2007. The survey periods were classified by Oceanic Ni$\tilde{n}$o Index as a weak El Ni$\tilde{n}$o in 2006 and a medium La Ni$\tilde{n}$a in 2007. The survey instruments were used to acquire data on CTD (Conductivity Temperature and Depth), XBT (Expendable Bathythermograph), and TSG (Thermosalinograph). The dominant temporal variation of surface temperature was diurnal. The diurnal variation in 2007, when the La Ni$\tilde{n}$a weather pattern was in place, was stronger than that in 2006. Surface salinity in 2006 was affected by a northwestward branch of North Equatorial Current, which implies that the El Ni$\tilde{n}$o affects surface properties in the North Equatorial Current region. Two salinity minimum layers existed at stations east of Chuuk in both year's observations. The climatological vertical salinity section along $180^{\circ}E$ shows that the two salinity minimum layers exist in $2^{\circ}N{\sim}12^{\circ}N$ region, consistent with our observations. Analysis of isopycnal lines over the salinity section implies that the upper salinity minimum layer is from intrusion of the upper part of North Pacific Intermediate Water into the lower part of South Pacific Subtropical Surface Water and the lower salinity minimum layer is from Antarctic Intermediate Water.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.6
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• pp.331-340
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• 1988

Using the oceanographic data during 196s~ 1983, the seasonal variation of the water type in the Tsushima Current is discussed by analyzing the thermosteric anomaly $(\delta_T)$. By investigating with the index of $33.8\%_{\circ}$ in salinity, it is shown that the low saline water inflowed through the Korea Strait affects the variations of water type in surface layer from summer to fall. On the sea surface, the value of $\delta_T$ is affected mainly by the sea surface temperature (SST). However, in summer, $\delta_T$ is temporarily influenced by the transitional characteristic of the surface salinity. It has the minimum value in winter when the SST is the highest and the sea surface salinity is the lowest. In fall, it decreases as the SST decreases. Specifically, the value of $\delta_T$ is 779 cl/t in August in the region of Korea Strait and 667 cl/t in September in the East Coast of Korea. These values are larger than that of the Kuroshio where is 622 cl/t in August. This phenomenon is due to the inflow of low saline water into these area during summer. In loom depth, the seasonal variation of the $\delta_T$ is not so significant as the surface and is mainly dependent on the annual temperature variation. In general, $\delta_T$ decreases as the Tsushima Current flows to the north.

• Water Engineering Research
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• v.2 no.1
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• pp.49-61
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• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model(KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS(Geographic Information Systems), and generates the distributed results by ASCII-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulated surface and subsurface flow, respectively (Kim, 1998; Kim et al., 1998). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts single overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 $\textrm{km}^2$ watershed located in the tideland reclaimed ares of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.2
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• pp.64-69
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• 2010

We investigated the variation in contact angle of a nano-sized water droplet on a nano stripe-patterned surface using molecular dynamics simulation. By changing the height and width of the stripe pillar, and the gap width of the stripes, we observed the contact angle of water droplet in equilibrium. When the surface energies were 0.1 and 0.3 kcal/mol, the calculated contact angles were in good agreement with the Cassie and Baxter equation. However, when the surface energy is 0.5 kcal/mol, the contact angles are observed to be perturbed along the Cassie and Baxter equation.

• Solar Energy
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• v.20 no.1
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• pp.55-62
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• 2000

An experimental study on the stratified fluids with water and silicon oil of same volume in the cavity with upper cooling surface was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in a square cavity. The experiments were performed with variation of initial temperature and cooling surface temperature. The temperature drop of oil was faster than that of water and freezing was initiated from the interface of oil and water and propagated downward. For the water above $4^{\circ}C$, the cooling rate was faster than that below $4^{\circ}C$ and showed almost same temperature distribution but for the water that of below $4^{\circ}C$, it showed the stable stratified temperature distribution. The lower the initial temperature and the higher the cooling surface temperature was, the longer the supercooling duration.

• Korean Journal of Environmental Biology
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• v.18 no.1
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• pp.21-31
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• 2000

We investigated seasonal variation of microalgal assemblages, sea water temperature, salinity and suspended solid and the parameters measured daily from January 1998 to October 1999 at a nearshore shallow-water in Marian Cove, Maxwell Bay, King George Island, the Antarctic. Annual mean surface water temperature was -0.3$0^{\circ}C$ and the highest water temperature was 4.53$^{\circ}C$ (22 January 1999) and the lowest water temperature was -2.07$^{\circ}C$ (23 August 1998). Annual mean salinity was 33.38 psu, ranging from 42.80 psu (6 January 1999) to 19.50 psu (6 June 1999). Annual mean suspended solid (SS) during two years was 34.14 mgㆍ1$^{-1}$, ranging from 60.62 mgㆍ1$^{-1}$(7 March 1998) to 12.90 mgㆍ1$^{-1}$ (26 December 1998). Chlorophyll $\alpha$ (Chl $\alpha$) concentrations were measured in order to know seasonal variations of microalgae in the surface seawater. Annual mean of total Chl a concentration was 0.55$\mu\textrm{g}$ㆍ1$^{-1}$, the highest Chl $\alpha$ concentration (12.16$\mu\textrm{g}$ㆍ1$^{-1}$) appeared in 4 October 1998, the lowest Chl $\alpha$ concentration appeared 0.19$\mu\textrm{g}$ㆍ1$^{-1}$, Monthly mean total Chl $\alpha$ concentration was high in October 1998 (1.32$\mu\textrm{g}$ㆍ1$^{-1}$) and low in July on 1998 (0.28$\mu\textrm{g}$ㆍ1$^{-1}$). Annual mean nano-sized Chl $\alpha$ concentration was 0.40$\mu\textrm{g}$ㆍ1$^{-1}$, monthly mean nano -sized Chl $\alpha$ concentration was high in November 1998 (0.90$\mu\textrm{g}$ㆍ1$^{-1}$), and low in July 1999 (0.22$\mu\textrm{g}$ㆍ1$^{-1}$). Annual mean micro-sized Chl $\alpha$ concentration was 0.15$\mu\textrm{g}$ㆍ1$^{-1}$ monthly mean micro-sized Chl $\alpha$ concentration was high in October 1998 (0.81$\mu\textrm{g}$ㆍ1$^{-1}$), and low July 1998, January, February and September 1999 (0.05$\mu\textrm{g}$ㆍ1$^{-1}$). More than 65% of total Chl $\alpha$ was concentrated during spring and summer time between October and March. Microalgal variation appeared to be due to physical factors of seawater in the Antarctic nearshore from 1998 to 1999. The reason why micro-sized Chl $\alpha$ did not increase during austral summer was the bay had been frozen by decrease of water temperature. We think that total microalgal abundance was decreased because the summer microalgal abundance was determined by variation of water temperature during winter season. [Chl $\alpha$ concentration, Microalgal assembalges, Seasonal variation, the Antarctic nearshore].

• Journal of Environmental Health Sciences
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• v.14 no.1
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• pp.47-53
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• 1988

This study was performed to investigate a seasonal and vertical variation of the nutrients, water temperature, pH, DO, BOD, COD in Sukchon lake from May 1985 to Jan. 1986. The results were as follows. 1. Vertical descent of water temperature was the remarkable situation on Jul. and difference between surface layer and bottom layer was 3.5$\circ$C. 2. The value of pH was average 8.0 in both lake. The value of pH in the winter was average 7.6, and Summer was average 8.3. 3. The contents of dissolved oxygen was the highest value (13.0mg/l in surface layer on Jan. and the lowest value (8.1mg/l in bottom layer on Ul. 4. The contents of PO$_4$-P, NH$_3$-N, NO$_3$-N and T-N were 0.03~O.17mg/l 0.12~0.34mg/l 0.36~0.91mg/l and 0.76~1.37mg/l respectively.

• Journal of Ocean Engineering and Technology
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• v.14 no.3
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• pp.35-40
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• 2000

SMAC method is, one of the numerical simulation techniques, modified from the original MAC for the time-dependent variation of fluid flows. The Navier-Stokes equation for incompressible time-dependent viscous flow is applied and, also marker particles which move with the fluid are used. Two-dimensional numerical computations of fluid flow are carried out in a virtual water tank. This paper has shown very well the movements of marker particles using SMAC method.