• Title/Summary/Keyword: Ocean circulation

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The characteristics and structures of thermal front and warm eddy observed in the southeastern part of the east sea in 1995 (95년 한국동해에서의 수온전선과 와동류의 구조 및 특성조사)

  • Lim, Keun-Sik;Wang, Kap-Sik;Yun, Jae-Yul;Kim, Ki-Cheol;Kim, Young-Gyu;Kim, Kuh
    • Journal of Ocean Engineering and Technology
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    • v.10 no.2
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    • pp.120-135
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    • 1996
  • The characteristics and fluctuations of structures and spatial distributions of thermal fronts and warm eddy in the Southeastern part of the East sea are discussed based on the data collected by the Naval Academy, Korea during Feb. 6-9, May 9-19 and Oct. 12-18, 1995. The thermal fronts existed very often at the sea off the Pohang-Ulsan, The generation of the thermal front is related with the development of the North Korea Cold Current. The warm eddy is located in the central part of the Ulleung basin where the local depth exceeds 1500m. This warm eddy is a major contributor to mass transport in the northern part of the East Sea. It is evident that knowledge of warm eddy is important in understanding the circulation in the western part of the East Sea.

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Semi-submersible Drilling Rig and Drilling Equipment (반 잠수식 시추선 및 주요장비에 대한 이해)

  • An, Byoung-Ky;Oh, Hyun-Jung
    • Journal of Ocean Engineering and Technology
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    • v.26 no.6
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    • pp.86-92
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    • 2012
  • An exploration well is drilled where oil or gas potential is shown by a seismic survey and interpretation. With the advance of drilling technology, most of the easily accessible oil had been developed by the end of the 20th century. To satisfy the ever increasing demand for oil, and bolstered by high oil prices, the major oil companies started to drill in deep water, which requires a deep offshore drilling unit. Offshore drilling units are generally classified by their maximum operating water depth. Many semi-submersible rigs have been purpose-designed for the drilling industry as the allowable drilling water depth has become deeper by the developed technics since the first semi-submersible was launched in 1963. Semi-submersible rigs are commonly used for shallow to deep water up to 3,000 m. Drilling equipment such as a top drive, blowout preventer, drawworks and power system, mud circulation system, and subsea wellhead system are explained to help with an understanding of offshore drilling procedures in the oil and gas fields. The objective of this paper is to introduce the main components of a semi-submersible rig and, by doing so, to raise the awareness of offshore drilling, which accounts for over 30% of the total oil production and will continue to increase.

Clay Minerals of the Bottom Sediments on the Northwestern Continental Shelf in the East China Sea

  • Park, Yong-Ahn;Khim, Boo-Keun;Nam, Jung-Man;Youn, Jeung-Su
    • Journal of the Korean earth science society
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    • v.25 no.1
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    • pp.1-9
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    • 2004
  • The clay minerals of thirty-four bottom sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more-than 70% of whole clay fraction. The highest concentration of illite (>72%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Cheju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where the fine-grained sediments are discharged from the modern and ancient Huanghe River. The relatively high abundance of kaolinite is likely derived from the Changjiang River via Taiwan ·Warm Current. In contrast, the large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern are, reflecting the transportation by the Huanghai Sea Coastal Current from the southern Yellow Sea.

On the Characteristics of the Oceanic Condition in the Surface Layer of the Northwestern East Sea (Japan Sea) (동해 북서해역의 표층해황 특성)

  • 김철호
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.8 no.2
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    • pp.215-220
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    • 1996
  • Seasonal and interannual variations of the oceanic condition in the surface layer of the northwestern East Sea are described. The seasonal variation shows two types in the water circulation. In the first type the East Korean Warm Current (EUC) Water are dominant in the East Korean Bay in spring, while in summer the cold water region develops as the North Korean Cold Current (NKCC) becomes strong. In the second type the cold water appears in the East Korean Bay from spring, but in summer the EKWC comes close to the coast, thus influencing the coastal cold water region. The characteristics of the interannual variation can be classified into 4 types according to the relative strength between the EKWC and the NKCC, and the paths of these currents. In each case various sizes of cyclonic cold eddies and/or anti-cyclonic warm eddies are formed frequently in the East Korean Bay.

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Characteristics of Typhoon Jelawat Observed by OSMI, TRMM/PR and QuikSCAT

  • Lim, Hyo-Suk;Choi, Gi-Hyuk;Kim, Han-Dol
    • Korean Journal of Remote Sensing
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    • v.16 no.4
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    • pp.293-303
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    • 2000
  • The typhoon Jelawat, which was formed over the tropical Pacific ocean on August 1, 2000 and made a landfall over China on August 10, 2000, was observed by Korea Multi-purpose Satellite (KOMPSAT-1) Ocean Scanning Multispectral Imager (OSMI), Tropical Rainfall Measuring Mission (TRMM)/Precipitation Radar(PR) and Quick Scatterometer (QuikSCAT). In spite of discontinuous observation, important mesoscale features of typhoon depending on life cycle were detected prominently. It is possible to distinguish on the OSMI photograph between the eye-wall convection and the stratiform and other convective clouds near the center of typhoon Jelawat. The TRMM/PR observations show quite clearly the eye-wall convection, stratiform regions, and convective bands. Vertical cross section of rainfall in the genesis stage of typhoon Jelawat exhibits circular ring of intense convection surrounding the eye. The mature stage of typhoon Jelawat consists of a strong rotational circulation with clouds which are well organized about a center of low pressure. The OSMI, TRMM/PR and QuikSCAT measurements presented here agree qualitatively with each other and provide a wealth of information on the structure of typhoon Jelawat.

Analysis of energy-saving effects of recirculation aquaculture system using seawater source heat pumps and solar power generation (해수 열원 히트펌프와 태양광 발전을 이용한 순환여과식 양식장의 에너지 절감 효과 분석)

  • Jong-Hyeok RYU;Hyeon-Suk JEONG;Seok-Kwon JEONG
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.60 no.2
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    • pp.194-206
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    • 2024
  • This study focuses on analyzing the energy-saving effects of the recirculation aquaculture system using seawater source heat pumps and solar power generation. Based on the thermal load analysis conducted using the transient system simulation tool, the annual energy consumption of the recirculation aquaculture system was analyzed and the energy-saving effects of utilizing the photovoltaic system was evaluated. When analyzing the heat load, the sea areas where the fish farms are located, the type of breeding tank, and the circulation rate of breeding water were taken into consideration. In addition, a method for determining the appropriate capacity for each operation time was examined when applying the energy storage system instead of the existing diesel generator as an emergency power, which is required to maintain the water temperature of breeding water during power outage. The results suggest that, among the four seas considered, Jeju should be estimated to achieve the highest energy-saving performance using the solar power generation, with approximately 45% energy savings.

Change of Oceanographic Environment in the Nakdong Estuary (낙동강 하구에서의 해양 환경 변화)

  • JANG SUNG-TAE;KIM KI-CHEOL
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.11 no.1
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    • pp.11-20
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    • 2006
  • The Nakdong Estuary is complex water system, where sea water and fresh water meet each other. It has undergone the significant change of its environmental conditions since the construction of the Nakdong River Barrier in 1987. Prior to its construction, mixing and circulation processes in the Nakdong Estuary was dominated by tidal current. However, after the dam construction, those processes were greatly altered by the artificial control of the fresh river water discharge. In this paper, the influence of opening and closing the floodgate of Nakdong River on the outflow behavior of estuarine water from the Nakdong Estuary is analyzed in detail.

Korean Ocean Forecasting System: Present and Future (한국의 해양예측, 오늘과 내일)

  • Kim, Young Ho;Choi, Byoung-Ju;Lee, Jun-Soo;Byun, Do-Seong;Kang, Kiryong;Kim, Young-Gyu;Cho, Yang-Ki
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.18 no.2
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    • pp.89-103
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    • 2013
  • National demands for the ocean forecasting system have been increased to support economic activity and national safety including search and rescue, maritime defense, fisheries, port management, leisure activities and marine transportation. Further, the ocean forecasting has been regarded as one of the key components to improve the weather and climate forecasting. Due to the national demands as well as improvement of the technology, the ocean forecasting systems have been established among advanced countries since late 1990. Global Ocean Data Assimilation Experiment (GODAE) significantly contributed to the achievement and world-wide spreading of ocean forecasting systems. Four stages of GODAE were summarized. Goal, vision, development history and research on ocean forecasting system of the advanced countries such as USA, France, UK, Italy, Norway, Australia, Japan, China, who operationally use the systems, were examined and compared. Strategies of the successfully established ocean forecasting systems can be summarized as follows: First, concentration of the national ability is required to establish successful operational ocean forecasting system. Second, newly developed technologies were shared with other countries and they achieved mutual and cooperative development through the international program. Third, each participating organization has devoted to its own task according to its role. In Korean society, demands on the ocean forecasting system have been also extended. Present status on development of the ocean forecasting system and long-term plan of KMA (Korea Meteorological Administration), KHOA (Korea Hydrographic and Oceanographic Administration), NFRDI (National Fisheries Research & Development Institute), ADD (Agency for Defense Development) were surveyed. From the history of the pre-established systems in other countries, the cooperation among the relevant Korean organizations is essential to establish the accurate and successful ocean forecasting system, and they can form a consortium. Through the cooperation, we can (1) set up high-quality ocean forecasting models and systems, (2) efficiently invest and distribute financial resources without duplicate investment, (3) overcome lack of manpower for the development. At present stage, it is strongly requested to concentrate national resources on developing a large-scale operational Korea Ocean Forecasting System which can produce open boundary and initial conditions for local ocean and climate forecasting models. Once the system is established, each organization can modify the system for its own specialized purpose. In addition, we can contribute to the international ocean prediction community.

Cloud Detection Using HIMAWARI-8/AHI Based Reflectance Spectral Library Over Ocean (Himawari-8/AHI 기반 반사도 분광 라이브러리를 이용한 해양 구름 탐지)

  • Kwon, Chaeyoung;Seo, Minji;Han, Kyung-Soo
    • Korean Journal of Remote Sensing
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    • v.33 no.5_1
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    • pp.599-605
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    • 2017
  • Accurate cloud discrimination in satellite images strongly affects accuracy of remotely sensed parameter produced using it. Especially, cloud contaminated pixel over ocean is one of the major error factors such as Sea Surface Temperature (SST), ocean color, and chlorophyll-a retrievals,so accurate cloud detection is essential process and it can lead to understand ocean circulation. However, static threshold method using real-time algorithm such as Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Himawari Imager (AHI) can't fully explained reflectance variability over ocean as a function of relative positions between the sun - sea surface - satellite. In this paper, we assembled a reflectance spectral library as a function of Solar Zenith Angle (SZA) and Viewing Zenith Angle (VZA) from ocean surface reflectance with clear sky condition of Advanced Himawari Imager (AHI) identified by NOAA's cloud products and spectral library is used for applying the Dynamic Time Warping (DTW) to detect cloud pixels. We compared qualitatively between AHI cloud property and our results and it showed that AHI cloud property had general tendency toward overestimation and wrongly detected clear as unknown at high SZA. We validated by visual inspection with coincident imagery and it is generally appropriate.

Permeable Coastal Pavement Structure for Shore Protection and Removal of Non-point Source Pollutants (연안재해 방지 및 비점오염원 유출저감을 위한 투수블록의 특성 연구)

  • Choi, Yun-Shik;Kim, Jong-Yeong;Han, Sangsoo;Kwon, Soonchul
    • Journal of Ocean Engineering and Technology
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    • v.33 no.6
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    • pp.597-606
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    • 2019
  • Due to climate change, coastal areas are being flooded with torrential rain, typhoons, and tsunamis. In addition, non-point source pollutants (NPSs) that accumulated on the ground, streets, and buildings during the dry season are washed off by rain and stormwater runoff, which adds to the damage associated with environmental pollution, e.g., pollution that makes its way into the ocean. Recently, low impact development (LID) has been considered as a means of controlling water circulation and NPSs. In the coastal area, permeable blocks have been constructed mainly to reduce the flood damage caused by waves. Some important design factors that must be considered to ensure long-term performance are the permeability coefficient, clogging, and the efficiency of the removal of total suspended solids (TSS), but currently there are no standardized design criteria or testing techniques that are used worldwide. Herein, we analyzed the permeability coefficient and the TSS removal efficiency tendency according to the permeability area ratio with an easily-detachable, permeable block filled with calcinated yellow soils as the filter media. Our lab-scale tests indicated that, when the permeability area ratio was 25%, the reduction of the permeability coefficient after clogged was 11%, which was a significant decrease compared to other cases. Permeability persistence increased when the permeability area ratio increased from 50% to 75%. The TSS removal efficiency decreased as the permeability area ratio increased. Our pilot-scale test indicated that the TSS removal efficiency was more than 80% higher in all cases. We also found that the permeability persistence was excellent as the permeability area ratio increased, and, in actual construction, it is effective to set 5.3% of the total area as permeable area in terms of permeability and economic feasibility.