• Title, Summary, Keyword: Neap tide

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DISTRIBUTION OF MERCURY, CADMIUM, COPPER, LEAD AND ZINC IN SEA WATER OF ULSAN BAY (울산만해수중의 수은, 카드뮴, 구리, 납, 아연의 농도분포)

  • WON Jong Hun;PARK Chung Kil;YANG Han Serb
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.9 no.3
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    • pp.177-184
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    • 1976
  • The concentrations of mercury, cadmium, copper, lead and zinc in sea water of Ulsan Bay were determined at spring and neap tide in August 1976. The range and mean of the heavy metal concentrations are as follows: at spring tide mercury 0.00-0.20ppb, 0.06ppb, cadmium 0.00-1.80ppb, 0,22ppb; copper 0.83-10.60ppb, 1.67ppb; lead 0.00-4.53ppb, 1.35ppb; zinc 0.0-21.8ppb, 4.4ppb, and at neap tide mercury 0.00-0.10ppb, 0.03ppb; cadmium 0.00-0.54ppb, 0.19ppb; copper 0.51-2.60ppb, 0.92ppb; lead 0.00-2.21ppb, 1.00 ppb; zinc 0.0-13.6ppb, 3.3ppb respectively. The concentrations and variations of the heavy metals were higher at spring tide than that at neap tide. The heavy metal levels of Ulsan Bay except Ulsan Harbour area was not higher than those of other coastal area. Low chlorosity, low pH and high heavy metal levels except zinc were determined in Ulsan Harbour at spring tide.

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Subtidal Zonation of the Cumacean Bodotria biplicata in the Surf Zone of Dolsando, Southern Korea (돌산도 쇄파대에 사는 쿠마류 Bodotria biplicata의 조하대 대상분포)

  • SUH Hae-Lip;KOO Young Kyung
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.30 no.1
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    • pp.39-45
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    • 1997
  • Subtidal zonation of a cumacean Bodotria biplicata was investigated in the sandy shore surf zone of Dolsando, southern Korea. Three replicate samples were taken with a sledge net at three sites, such as the surface and bottom of 1 m depth and waters edge, at hourly intervals over the neap and spring tide cycles on January 1993 (n=225). B. biplicata, the most dominant cumacean in this area, exhibited peak density at the bottom while about $0.6\%$ of total catch was collected at the surface. Mean density during the neap tide cycle was slightly higher than that during the spring tide cycle. The depth of subtidal zone influenced the total catch of B. biplicata. The changes in density were related to the depth of subtidal zone rather than day-night cycle or ebb-flood tide. The results obtained in this study suggest that the diel vertical migration is not distinct. During both neap and spring tide cycles, B. biplicata attained a density maximum at the same level of about 90 cm below lower low water (LLW). It is likely, therefore, that this species performs shore- and seaward horizontal migration fortnightly. The speed and distance of migration may be directly related to the beach slope and tide range. Ontogenetic differences in subtidal distribution were observed. Juveniles and manca larvae tended to occur lower areas than the adults. Such differences may reduce intraspecific competition for diets.

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Acoustic analysis on the shape of gill-net in the current (자망의 수중형상에 대한 음향학적 해석)

  • Han, Jin-Seok;Shin, Hyeon-Ok
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.43 no.2
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    • pp.116-125
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    • 2007
  • An experiment to acoustically analyze the shape of gill-net in the current was conducted in Jaran Bay, Gosung, Korea on the 9th to 10th September(spring tide) and 28th to 29th September(neap tide) 2006. It was measured by a 3D underwater positioning system with a radio-acoustic linked positioning buoys. Six of 7 acoustic transmitters used in the experiment were attached on the float line of the gill-net and the other was fixed on the sea bed. During spring tide, the maximum movement of the gill-net was 27.0m(22:00) in the west(4.4cm/s, $311.9^{\circ}$) and 20.6m(04:00) in the east(3.9cm/s, $66.5^{\circ}$). The maximum extension of the gill-net(the distance between P1 and P6) was 119.8m(21:00, 11.6cm/s, $321.9^{\circ}$) and the minimum was 109.9m(23:00, 16.1cm/s, $88.5^{\circ}$). During neap tide, the maximum movement was 38.0m(20:00) in the east(9.6cm/s, $278.2^{\circ}$) and 11.0m(12:00) in the west(1.9cm/s, $232.1^{\circ}$). The maximum extension was 99.6m(14:00, 12.5cm/s, $94.7^{\circ}$) and the minimum was 85.0m(06:00, 9.0cm/s, $265.8^{\circ}$). During spring tide, the maximum height of the gill-net from the sea bed was 3.7m(02:00, 7.4cm/s, $151.6^{\circ}$) and the minimum was produced the three times as 1.5m. At that time, the current speed and direction was 17.9cm/s and $85.3^{\circ}$(23:30), 16.1cm/s and $249.4^{\circ}$(05:00), and 13.7cm/s and $291.4^{\circ}$(06:30), respectively. During neap tide, the maximum height was 3.6m(12:30, 2.1cm/s, $242.3^{\circ}$) and the minimum was 1.5m(14:00, 12.5cm/s, $94.7^{\circ}$).

Tidal Exchange of Sea Water in Koje Bay (거제만의 해수교환)

  • KIM Jong-Hwa;CHANG Sun-Duck
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.18 no.2
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    • pp.101-108
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    • 1985
  • The sea water exchange of Koje Bay in the southeastern part of the Korean Peninsula was estimated on the basis of current measurements and oceanographic observation. The exchange ratio was estimated by salinity differences and tidal prism method. The range of exchange ratio at the central part at the entrance of the bay is estimated to be around $26\%$ at spring tide and 5 to $15\%$ at neap tide. The magnitude of exchange ratio, however, can be changed due to water exchange, hydrometeorological and geomorphological conditions. The flushing time deduced by tidal prism was about 48 hours at spring tide and 81 hours at neap tide. Tidal induced eddy motion may play an important role on the seawater exchange in the bay.

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Three-Dimensional Numerical Model Experiments of Tidal and Wind-Driven Currents in Chinhae Bay (진해만 조류 및 취송류의 3차원 수치모형실험)

  • KIM, CHA-KYUM
    • 한국해양학회지
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    • v.29 no.2
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    • pp.95-106
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    • 1994
  • Tidal and wind-driven currents in Chinhae Bay are investigated using a three-dimensional numerical model developed by Kim et al. (1993). The simulations indicate that the flow patterns in the bay are predominated by the bathymetry, wind and river inflow, and the effects of wind on the flow pattern in the inner bay are much stronger than those in the entrance channel. Computed tidal currents coincide with the field measurements. The horizontal and vertical velocities of tidal and residual currents are strong in the entrance channel of the bay, whereas the velocities are relatively weak in the western and northern parts of the bay. Computed velocity fields show the expected phase difference between the velocities in the surface and those in the bottom layer, and these characteristics are more remarkable during the spring tide than the neap tide. The surface currents in the bay depend strongly on the wind and river inflow, and such phenomena are more remarkable during the neap tide than the spring tide.

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The Relation of Cross-sectional Residual Current and Stratification during Spring and Neap Tidal Cycle at Seokmo Channel, Han River Estuary Located at South Korea (대.소조기시 한강하구 석모수로에서 단면 잔차류와 성층간의 관계 연구)

  • Choi, Nak-Yong;Yoon, Byung-Il;Kim, Jong-Wook;Song, Jin-Il;Lim, Eun-Pyo;Woo, Seung-Bhum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.3
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    • pp.149-158
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    • 2012
  • This study analyzed cross-sectional variations in residual current and strengths of stratification by observing cross-sectional velocity and salinity during spring tide and neap tide, respectively, for continuous 13-hour periods at 2 observation lines at northern and southern end of Seokmo Channel, which is located west of Ganghwado. Salinity distribution of channel depends on not only neap and spring tide but also impact of salinity. The residual current component was obtained by removing $M_2$ and $M_4$ tidal components that were extracted using the least squares method on 13-hour velocity component. Cross-section of residual velocity at northern and southern end of Seokmo Channel exhibited southward residual components at channel's surface layer, but northward residual current was observed at channel's bottom layer, clearly showing a 2-layer tidal circulation between surface and bottom layers. The variation in location of appearing northward residual current according to changes in spring and neap tidal cycle and its correlation with stratification were analyzed using the Richardson number and Simpsonhunter index. At northern and southern end of Seokmo Channel, northward residual current appears in the location where Richardson number is large, Simpson-hunter index appears as a value greater than 4.

Two-Dimensional Hydraulic and Numerical Modeling of tidal Currents in Chinhae Bay (鎭海灣 潮流의 2차월 水利 및 數値 모델링)

  • 김차겸;장선덕
    • 한국해양학회지
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    • v.29 no.2
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    • pp.83-94
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    • 1994
  • Two-dimensional tidal and tidal residual currents in Chinhae Bay are investigated by field observations, hydraulic and numerical experiments. The results of hydraulic and numerical model experiments roughly coincide with the field measurements. Maximum tidal currents during the spring and neap tides in Kaduk and Kyunnaeryang channel and the central channel of Chinhae Bay are strong as 90 to 110 and 30 to 40 cm/s respectively, and strong tidal residual currents having numerous eddies take place. Maximum tidal currents during the spring and neap tides in the western and northern parts of the bay are weak as below 30 and 10 cm/s respectively, and also tidal residual currents are relatively weak. Tidal residual currents in the northern part of Kajo-do go toward the north, whereas the currents in the southern part move down the bay, and the currents rotating clockwise occur around Bu-do. The surface currents in the bay depend strongly on the wind and river inflow, and such phenomena are more remarkable during he neap tide than the spring tide.

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Study on Lateral Flow Distribution and Momentum Analysis at Flood season and Neap tide of the Seokmo Channel in the Han River estuary (소조기 홍수시 한강하구 석모수로에서의 횡 방향 2차 흐름 및 운동량 분석)

  • Choi, Nak Yong;Woo, Seung-Buhm
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.6
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    • pp.390-399
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    • 2012
  • This research observed the cross section current of 7 survey lines in Seokmo Channel of Gyeonggi bay with a lot of freshwater inflow and S-shaped for 13 hours during flood season and neap tide. We indicated the distribution of the current velocity by comprehending the speed and direction of the current velocity of each line during maximum flood, ebb tide and observed the distribution of salinity. Moreover, in order to understand what lateral momentum causes the lateral flow in each survey line, we practiced the momentum analysis through the observation data. As a result, the lateral baroclinic pressure gradient force and vertical friction of the Seokmo channel during neap tide were the strongest, and this is why the flow by the distribution of salinity and stratification most often occurs. In north of the Seokmo channel, where have wide intertidal and a lot of freshwater inflow, the secondary circulation is caused by balance of lateral baroclinic pressure gradient force and other forces, and the vertical friction was strong in the lines with small depth. On the other hand, in the southern part of the Seokmo channel where the water is deep and the waterway is curved, the advective acceleration and centrifugal force become stronger by the geographical causes during ebb and the influence of fresh water. Therefore, the lateral flow in the Seokmo channel was caused by the distribution of the momentum that differs by location, depth, curve, etc.

The Distribution and Behaviors of Suspended Matters in Seomjin River Estuary - Compared with Rainy and Wet Season - (섬진강하구에서 부유물질의 분포와 거동 - 풍수기와 평수기의 비교 -)

  • Kim, Seok-Yun;Lee, Byoung Kwan
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.935-942
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    • 2009
  • During period of the rainy season of spring tide Aug. 2005, the suspended sediment transport rate from Seomjin River increased ten times as high as neap tide of low river discharge. During ebb tide of high terrestrial input, the grain size of suspended particles of both surface and bottom layer of the water column, showed a uni-modal distribution with a dominant peak at coarse fraction, which suggests a characteristic development of floc-sized particles of low mean effective density. On the contrary, the particles supplied toward upstream of Seomjin river from Gwangyang Bay during flood tide showed a bi-modal distribution with a secondary peak at finer fraction, possibly due to the resuspension and the deflocculation associated with the increased shear velocity at near bottom. Break-up of large flocs is also suggested by the increased mean effective density. However, settling velocity was lower during flood tide because of smaller grain size. Thus, net deposition of suspended sediment is expected at within Gwangyang Bay instead of upstream of Seomjin River, even though suspended sediment transport rate at near bottom water was three times higher than that at surface water during flood tide.

Acoustic Doppler Current Profiler Bottom Tracking Survey of Flow Structures around Geumo Archipelago in the Southern Waters of Korea (ADCP bottom tracking에 의한 금오열도 주변의 해수유동)

  • Choo, Hyo-Sang
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.5
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    • pp.589-600
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    • 2019
  • In order to investigate the flow structures around Geumo archipelago on Southern Waters of Korea, water movements were measured for 25 hours during spring tide in May and neap tide in September 2002 using ADCP (Acoustic Doppler Current Profiler) attached to a running boat. Dominant directions of ebb and flood current at spring tide are SE-NW, representing the average flow rate of approximately 40cm/s in the surface layer. However because of the topographical reason, the direction and speed of the flow in the narrow waterway sea area around the northwest of Gae Island were different. There was no notable baroclinic component of tidal flow at spring tide. This indicates that the sea area has been actively engaged in vertical mixing due to island wake or eddy due to narrow waterways, shallow water depth and rapid flow rate around archipelago. At neap tide, dominant directions of tidal flows are SSE-NNW and the average flow rate in the surface layer is about 85 percent of the spring tide. The duration and intensity of the flow direction are shorter and less dominant than the spring tide. It is expected that asymmetrical tidal mixing will occur due to vertical velocity shear and horizontal eddies. From daily mean tidal flows obtained from the ADCP observation, it was found that the northwest of Gae Island have flows in NW~NE, the west of Geumo Island have the average currents of up to 21 cm/s WSW~SSW and counterclockwise circulation or eddy currents are formed in the west of Sori Island.