• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.190-197
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• 2008

Spatio-temporal distribution of eggs and larvae of Japanese anchovy Engraulis japonica in the southern sea of Korea was determined using data obtained from icthyoplanktonic surveys and oceanographic observations between Goheung Peninsula and Goeje Island from May to August 2007. Commercial anchovy catch and size composition from four local fishery cooperative associations were also analyzed in relation to the geographic distribution of eggs and larvae. The abundance of anchovy eggs increased from May to July and was lowest in August. Eggs were mainly distributed between Namhae Island and Goeje Island, where water temperatures were $15{\sim}24^{\circ}C$ and salinities were 32~35‰. In 2007 anchovy landings between Namhae Island and Goeje Island were 11,409 tons at Tongyeong association, 4,137 tons at Masan association, and 2,487 tons at Sacheon association. However, landings between Goheung and Yeosu Peninsula were only 4,411 tons (at Yeosu association). The catch by anchovy tow net was high in the area where eggs were abundantly distributed. This indicates that the distribution of egg density was directly correlated with recruitment of E. japonica. All growth stages were abundant in the study area, indicating that this area is a major spawning and growing ground of E. japonica in Korean waters.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.294-305
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• 1989

Basedon statistical data of pomfret (Pampus spp.) catches by the stow net during $1970\~1985$, the distribution and migration of pomfrets and fishing conditions were investigated in relation to oceanographic conditions, in the East China Sea and the Yellow Sea. The main fishing grounds of Pomfrets were formed around the Great Yangtze Sand Bank which locates between the Cheju Island and the mouth of the Yangtze River. Its area occupied only 11 percent of all fishing grounds, and about 70 percent of total catch was found there. The coefficient of variation(CV) in catch was below 0.01 in the whole fishing grounds and that of tile main fishing grounds (14 fishing areas) was $0.001\~0.003$. This area was indicated markedly by the inflow of Yellow Sea Warm Current from spring to autumn, and this mixing area which formed the oceanic front among the China Continental Shelf Water, the Yellow Sea Bottom Cold Water and the Tsushima Warm Current. The pomfrets migrates to south-north according to the expansion and contraction of the Tsushima Warm Current including the Yellow Sea Warm Current and the Yellow Sea Bottom Cold Water. Therefore, it migrates to north of the Yellow Sea in summer and to southern part of the East China Sea in winter. The most frequent range of the water type for high catch was $10\~12^{\circ}C$ in temperature and $32.4\~33.4\%_{circ}$ in salinity. The ranges was occupied more than 70 percent of total catch on fishing season. The frequency range of the water type was not different between the abundant fishing periods and the poor fishing periods in terms of the maximum catches.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.83-91
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• 1984

The formation and structure of tidal front in the eastern part of the Yellow Sea were studied based on the oceanographic data compiled during the periods of $1982{\sim}1983$ and $1966{\sim}1970$. Well-defined fronts occurring in the Yellow Sea in summer mark the boundary between the stratified and vertically mixed regimes. The occurrence of vertically mixed regimes may be interpreted in terms of available turbulent kinematic energy of tidal currents. The tidal frontal regions were determined by horizontal gradients of temperature, salinity and dissolved oxygen, and were verified by water colour and transparency. In summer the tidal fronts were found at depths of $15{\sim}25m$ at about 20 miles from the shore. Potential energy of vortical stratification in the tidal frontal region was 10 $Joule/m^3$. The stratification parameter in the frontal region computed from the numerical tidal model was $S_p=1.0.$ Tidal front is formed in regions with $S_p=1-1.5,$ if surface heat flux are constant. Waters in the stratified region have the layer structures of wind-mixed surface layer, thermocline and tidal-mixed bottom layer. In the vertically mixed region, however, sea water is nearly homogeneous. in winter no distinctive tidal front was seen.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.383-392
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• 2011

The basic research of the estuarine circulation at Gyeong-Gi bay has not been well studied up to now, although coastal development pressures have been continuously increased. To understand the oceanographic phenomena at the Han River estuary, it's essential to understand the propagation characteristic of tidal wave which is the strongest external forcing in this region. In this study, we investigate the tidal wave propagation characteristics along the 3 major channels using observation data and numerical model. It is found that 3 channels are all hyper-synchronous and the most important physical factor controlling the tidal wave propagation is topographical convergence of estuary shape and friction. The result of analytic solution at ideal channel considering the topographical convergence and friction show that the contribution of physical role of convergence and friction varies at 3 different channel. And the ratio of convergence and friction at Yeomha channel is four times larger than Seokmo channel. Because of this effect, the location of maximum amplitude at Yeomha channel is showed up downward than Seokmo channel. The ratio of decreasing amplitude and increasing phase per unit distance between stations is bigger than Seokmo channel. Although 3 major channel show a hyper-synchronous pattern, Yeomha shows more frictionally dominant channel and Seokmo channel is more dominantly affected by convergence effect.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.1-7
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• 1997

We have monitored nutrients, chlorophyll, suspended solids, and salinity in the Keum Estuary to understand the temporal fluctuation of oceanographic parameters and to illustrate any variation due to the gate operation of the Keum River Dike from June, 1995 to September, 1996, approximately for 500 days. Tidal range is used as the key factor to explain the fluctuations and atmospheric parameters such as air temperature, wind velocity and rainfall are also used supplementally. The fresh water discharge was selected as another major impact on the estuarine environment due to the gate operation of the Keum Dike. In addition, daily variation by tidal cycle was investigated twice in April and July, 1996. In diurnal variation, salinity was positively correlated with tidal elevation, whereas negatively correlated with nutrients. Relatively high suspended solid and chlorophyll contents were found in the period between high and low tide. In 500 days continuous observations, salinity was negatively correlated with the volume of fresh-water discharge, but positively correlated with nutrients. A major chlorophyll bloom occurred in spring. A similar pattern of variation was observed between suspended solid and the neap-spring tidal cycle. In comparison with the data of the Keurn Estuary before the gate operation of the Keum River dike, fresh-water discharge predominated other environmental factors during the rainy season. In addition, the velocity of tidal current and the concentration of suspended solid were decreased, while nutrients and chlorophyll contents were increased.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.105-111
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• 1985

Optical properties of sea water were studied in the entrance of Tokyo Bay, Japan, based on the data obtained from six oceanographic stations in April, 1985. The observation of surface irradiance and underwater irradiance of sea water for eight kind of wavelengths (378, 422, 481, 513, 570, 621, 653, 677 nm) of sun light was conducted using the underwater irradiameter (Isigawa # SR-8). The mean attenuation coefficient of the sea water was appeared to be 0.300 (0.034-0.774) and the attenuation coefficient of the sea water for wavelength appeared such as 0.230 for 378 nm, 0.258 for 422 nm, 0.266 for 481 nm, 0.213 for 513 nm, 0.195 for 570 nm, 0.378 for 621 nm, 0.402 for 653 nm, 0.498 for 677 nm. The transparency was 7.2 m (6-9.5 m) and water color was 9 (6.5-10.5) in the study area and the sun's altitude 52.56$^{\circ}$(31.68-66.76$^{\circ}$). The relationship between attenuation coefficient (K) and transparency (D) was K=2.61/D (1.76/D-4.13/D). The rates of light penetration for eight kind of wavelengths (378, 422, 481, 513, 570, 621, 653, 677 nm) were computed with reference to the surface light intensity respectively. The mean rates of light penetration in proportion to depths were 69.30% (57.33-77.40%) in 1 m layer. 17.66% (6.3-27.90%) in 5 m layer, 4.47% (0.60-9.17%) in 10 m layer, and 0.77% (0.02-1.97%) in 20 m layer. The rates of light penetration at the transparency layer with reference to the surface light intensity was shown as 9.91% (0.51-22.99%).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.273-283
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• 2020

Numerical simulations of the storm surge and waves induced by the Typhoon Bolaven incident on the west sea of Korea in 2012 are performed using the JMA-MSM weather field provided by the Japan Meteorological Agency, and the calculated surge heights are compared with the time history observed at harbours along the various coasts of Korea. For the waves occurring coincidentally with the storm surges the calculated significant wave heights are compared with the data measured using the wave buoys operated by the Korea Hydrographic and Oceanographic Agency and the Korea Meteorological Administration. Additional simulations are also performed based on the pressure and wind fields obtained using the best track information provided by the Joint Typhoon Warning Center, and the calculated results are compared and analyzed. The waves and storm surges calculated using JMA-MSM wether field agree well with the observations because of the better reflection of the topography and the pre-background weather field. On the other hand, the calculated results based on the weather fields produced using the JTWC best track information show some limitations of the general trend of the variations of wave and surge heights. Based on the results of this study it is found that the reliable weather fields are essential for the accurate simulation of storm surges and waves.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.2 s.29
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• pp.119-125
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• 2007

In order to illustrate the variation cf stratification and to know the effects of the temperature and the salinity on the stratification in the South Sea of Korea, the stratification parameter defined as potential energy anomaly (PEA, $V(J/m^3)$) introduced by Simpson and Hunter (1974) was used. The oceanographic data were obtained in August 1999 and February 2000 by National Fisheries Research and Development Institute (NFRDI). V in August is generally high in offshore and low in near shore. However, in February, V in the near shore is higher than that cf the offshore due to the vertical temperature gradient between surface and bottom layer caused by the expansion of South Korean Coastal Waters (SKCW). In summer, the increase of the atmospheric heating acts on the stratification as the buoyancy forcing. In most cases, the effect cf the temperature on the stratification is stronger than that of the salinity. The temperature effect is predominantly due to the extent of the intrusion of Tsushima Warm Current into the study area. However, at stations where V is high the effect of the salinity is also significant. In winter, V is very low due to the decrease cf the buoyancy forcing, but some stations show the relatively high V due to the expansion of SKCW and salinity in winter unlike that in summer makes the stratification weak.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.2
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• pp.86-96
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• 1997

In order to investigate the formation of a shallow water front and its relation to water quality distributions, oceanographic measurements were made, and the numerical computations of the Simpson-Hunter stratification parameter log(H/U$^3$) were performed. It is shown from satellite image and hydrographic data that the shallow water front is formed near the northern Kaduk channel, and the stratification parameter log(H/U$^3$) near the front is in a range of 2.0-2.5. Measured COD (Chemical Oxygen Demand) concentrations in offshore region of the front and in the western part of the bay are below 2.0 mg/1. whereas the concentrations in Masan Bay located in the northern inside of the frontal zone are high as 3.0-5.5 mg/1. COD concentrations decrease gradually from Masan Bay toward the offshore due to the dilution by strong water mixing. Anoxic and hypoxic water masses at the bottom layer in summcr occur in the western part of Chinhae Bay and in Masan Bay, and DO (Dissolved Oxygen) concentrations become low with increasing the stratification parameter. DO concentrations outside the front are more than about 4.0 mg/1, whereas the concentrations inside the front are low. The shallow water front plays a significant role for material transport from coastal area to oceanic area, and the frontal region seems to be important physical and chemical boundaries.