• Title/Summary/Keyword: 해양 전선

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Formation and Characteristic of Summer Fronts between Cheju and Shanghai (제주도-상해간 여름철 전선역 형성과 특성)

  • 허만영;최영환
    • Proceedings of the Korean Society of Fisheries Technology Conference
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    • pp.164-164
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    • 2000
  • 일반적으로 해양에서 전선이란 서로 다른 수괴간의 불연속면을 일컫는다. 이러한 전선의 양측 면에는 유속, 수온, 염분, 수질 등이 급변한다. 본 연구는 1997년 8월 26일부터 9월 2일까지 제주도 서부에서 중국 상해 양쯔강 하구역까지 21개 정점에서 관측된 물리ㆍ화학적 관측자료로부터 연안과 외양간의 수온, 염분, 밀도 등 물리적 인자 특성으로부터 전선역을 찾아내고 전선역을 중심으로 양측의 수질특성을 용존산소, 인산염, 질산염, 규산염 등 영양염류의 분포 특성과 아울러 생산력 인자인 엽록소 a의 분포량을 파악하여 전선역을 중심으로 한 수괴간의 특성을 규명하였다

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An Oceanic Front : The Formation of Tidal Fronts with Its Microscale Structure Evolution (해양전선 : 조석전선의 형성 및 그 미세구조의 전개 과정)

  • Yi-Gn Noh
    • International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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    • v.21 no.1
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    • pp.17-30
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    • 1993
  • The basic processes responsible for the generation of oceanic fronts were reviewed. In particular the process of a shelf sea front produced by tidal stirring was identified from the one dimensional model of the water column in the coastal area, which incorporates the microscale process for the formation of a tidal front. Also a new criterion to predict its location was suggested. The time evolutions of the distributions of density and turbulent kinetic energy calculated from the model show that the criterion for the formation of a thermocline can be predicted as $R{\delta}^4$~ constant for large $\delta$ ($\delta$>0.5), but the dependence on $\delta$ decreases as $\delta$ goes to O, where $R=H^4Q/{K_b}^3$,{\;}{\delta}=1-Do/H$, Q is the buoyancy flux at the surface, $K_b$ is the eddy diffusivity maintained at the bottom and Do is the depth of a thermocline in the absence of bottom mixing. The depth of a thermocline was found to decrease as the bottom mixing increases for a given value of Do. The results were interpreted in comparison with the previous studies.

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Analysis of Misconceptions on Oceanic Front and Fishing Ground in Secondary-School Science and Earth Science Textbooks (중등학교 과학 및 지구과학 교과서 조경 수역 및 어장에 관한 오개념 분석)

  • Park, Kyung-Ae;Lee, Jae Yon;Kang, Chang-Keun;Kim, Chang-Sin
    • Journal of the Korean earth science society
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    • v.41 no.5
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    • pp.504-519
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    • 2020
  • Oceanic fronts, which are areas where sea water with different properties meet in the ocean, play an important role in controlling weather and climate change through air-sea interactions and marine dynamics such as heat and momentum exchange and processes by which properties of sea water are mixed. Such oceanic fronts have long been described in secondary school textbooks with the term 'Jokyung water zone (JWC hereafter) or oceanic front', meaning areas where the different currents met, and were related to fishing grounds in the East Sea. However, higher education materials and marine scientists have not used this term for the past few decades; therefore, the appropriateness of the term needs to be analyzed to remove any misconceptions presented. This study analyzed 11 secondary school textbooks (5 middle school textbooks and 6 high school textbooks) based on the revised 2015 curriculum. A survey of 30 secondary school science teachers was also conducted to analyze their awareness of the problems. An analysis of the textbook contents related to the JWC and fishing grounds found several errors and misconceptions that did not correspond with scientific facts. Although the textbooks mainly uses the concept of the JWC to represent the meeting of cold and warm currents, it would be reasonable to replace it with the more comprehensive term 'oceanic front', which would indicate an area where different properties of sea water-such as its temperature, salinity, density, and velocity-interact. In the textbooks, seasonal changes in the fishing grounds are linked to seasonal changes in the North Korean Cold Current (NKCC), which moves southwards in winter and northwards in summer; this is the complete opposite of previous scientific knowledge, which describes it strengthening in summer. Fishing grounds are not limited to narrow coastal zones; they are widespread throughout the East Sea. The results of the survey of teachers demonstrated that this misconception has persisted for decades. This study emphasized the importance of using scientific knowledge to correct misconceptions related to the JWC, fishing grounds, and the NKCC and addressed the importance of transferring procedures to the curriculum. It is expected that the conclusions of this study will have an important role on textbook revision and teacher education in the future.

Temperature inversions observed in April in the eastern Yellow Sea (황해동부에서 4월에 관측 수온역전)

  • LEESANGHO
    • 한국해양학회지
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    • v.27 no.4
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    • pp.259-267
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    • 1992
  • A survey of CTD casting was taken in April 1991 in the eastern Yellow Sea. The vertical structure of water column consists of the upper mixed warm, the mid cold and the lower warm layers devised clearly by a seasonal thermocline and the temperature inversion. A strongest temperature inversion is found in the southern part of the survey area. Where the low-layer water is $3^{\circ}C$ higher than the mid-layer water. The area of the temperature inversion covers about $100{\;}km{\;}{\times}{\;}100{\;}km$ and it is observed 1.5 month later. The temperature and salinity of the low-layer water shows a core structure in vertical sections and the tongue-like distribution extending from the south to the north, implying that the warm and saline water found in the oceanic front south of the survey area in early spring is advocated to the north over 150 km underneath the Yellow Sea cold water.

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Improved Method for Feature Tracking Method in estimating Ocean Current Vectors from Sequential Satellite Imageries (연속 위성화상자료상의 향상된 형태추적법을 이용한 유속추정기법)

  • Kim, Eung;Ro, Young-Jae
    • Korean Journal of Remote Sensing
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    • v.16 no.3
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    • pp.199-209
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    • 2000
  • This study improves the feature tracking method (FTM) in estimating the ocean current vectors from the sequential AVHRR satellite imageries by adding the objective algorithm in defining the edges and boundaries of the oceanic eddies and fronts. It was implemented by using the Sobel operator. The Sobel operator has been proved to be in effective filter in detecting the edges of any object on the image. In estimating the current vectors on the edges defined by the Sobel operator, center coordinates of the Pattern and Search tiles need to be determined by the investigator. The objective feature tracking method combined with maximum cross correlation method (MCC) is turned out to be very efficient and fast, since it uses only parts of the image containing the objects instead of searching the entire image. In the validation with the in situ ADCP measurements of currents in the East Sea, the estimated current speed values are around 35% lower than and current directions are deviated by $34^{\circ}$ from ADCP current vectors. The results are regarded as improved ones compared to the previous investigators'.

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Formation and Characteristics of Ocean Fronts at the East China Sea in Southwestern Sea Area from Jeju Island, Summer (제주도 서남방 동중국해역에서 하계 해양전선 형성과 수질특성)

  • Heo M. Y.;Choi Y. C.
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.7 no.2
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    • pp.64-69
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    • 2004
  • The results of analyzing the hydrographic observations in the southwestern sea of Jeju Island in the last 10 days of August 1999 to investigate the characteristics of oceanic front area appeared in the East China Sea in August from is summarized as follows: In Line A, a front appears at Station A5 of 124°E and 31°30'N, showing relatively uniform density of 21.4 to 22.1 in the surface layer of 50m depth, which is distinguished from 22.0 shown in the sides of China and open ocean. In Line B, a front also appears at Station B6 of 124°E and 33°N, of which density is distinguished from 20.0 shown in the sides of China and open ocean as In Line A. As a result, the front area caused by fresh water runoffs from the Yangtze River in the East China Sea is formed at 124°E and 124°30'in the direction of east and northeast from Yangtze River, respectively. Nutrient concentrations in the study area are characterized by higher density in the side of China and by clear density difference between the upper and the lower layers in the side of open ocean, while by uniformly lower density concentration between the upper and the lower layers in the front area. Chlorophyll-α concentrations is high in the sides of China and open ocean, while low in the front area. Judging from the above results, the productivity in the front area is lower according to the inactivity of phytoplankton due to increased flow from vertical mixing between the upper layer and the lower layer. Also, the front area in the East China Sea in summer may be moved towards the adjacent sea of Jeju Island by increasing fresh water runoffs from the Yangtze River in summer.

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The Outbreak, Maintenance, and Decline of the Red Tide Dominated by Cochlodinium polykrikoides in the Coastal Waters off Southern Korea from August to October, 2000 (2000년 여름 남해안에 나타난 Cochlodinium polykrikoides 우점 적조의 발생 특성)

  • Jung, Chang-Su;Lee, Chang-Kyu;Cho, Yong-Chul;Lee, Sam-Geun;Kim, Hak-Gyoon;Chung, Ik-Kyo;Lim, Wol-Ae
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.7 no.2
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    • pp.68-77
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    • 2002
  • We investigated the outbreak, maintenance, and decline of the red tide dominated by C. polykrikoides in the coastal waters off Southern Korea from August to October, 2000, by combining field data and NOAA satellite images. In general, the C. polykrikoides blooms, which have occured annually in Korean coastal waters from 1995 to 1999, initiate between late August and early September around Narodo Island and expand to the whole area of the southern coast. However, initiation and short-term change of the bloom of 2000 were quite different from the pattern observed previously. In mid-August, thermal fronts in sea surface temperature(SST) were formed: 1) between the Tsushima Warm Current Water (TWCW) and the Southern Korean Coastal Waters (SKCW), 2) between the jindo cold water mass and the southwestern coastal waters, and 3) between the upwelled cold waters in the southeast coast and the offshore warm waters. Free-living cells of C. polykrikoides were concentrated in these frontal regions. In late August, the thermal front TWCW-SKCW approached the mouth of Yeosuhae Bay where Seomjin River water and anthropogenic pollutants from the Industrial Complex of Gwangyang Bay are discharged. In the blooms of 2000 initiated in Yeosuhae Bay in late August, the dominant species, C. polykrikoides, co-occured with Alexandrum tamarense, Gymnodinium mikimotoi, Skeletonema coastatum, and Chaetoceros spp. Two typhoons, 'Prapiroon' and 'Saomai' during and the C. polykrikoides bloom probably affected the abundance of this species. After the former typhoon passed the Korean Peninsula, cell growth of C. polykrikoides was maximal, but after the latter typhoon, the C. polykrikoides bloom disappeared (20 September). On 5 October, the blooms dominated by C. polykrikoides broke out within the coastal waters of Jinhae Bay and Hansan-Keoje Bay. NOAA satellite images showed that the isothermal line of 22$^{\circ}C$ extended into Jinhae Bay. In this bloom, C. polykrikoides also occurred simultaneously with Akashiwo sanguinea(=Gym-nodinium sangunium), a common red tide-forming dinoflagellate species in fall and winter in these coastal bays.