• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2003년도 춘계종합학술대회
• /
• pp.641-644
• /
• 2003

복수위성자료 신호처리기법을 사용해서 남인도양지역을 중심으로 한 해수면변화와 사행(meandering)을 연구하였다. 해수면변화는 아프리카 남부(46$^{\circ}$E)에서 크호제트 대지(Crozet basin) 의 35$^{\circ}$~46$^{\circ}$S대를 걸쳐서 암스테르담-케르겔른 경로(Amsterdam-Kerguelen Passage)까지 확장된다. 이때 가장 강한 해수면변화(20~30cm)가 2개의 좁은 지역에서 발생하는데, 하나는 경도 49$^{\circ}$~57$^{\circ}$E(약 700Km) 및 위도 38$^{\circ}$~42$^{\circ}$S(약 450km)나타났고 그리고 나머지 하나는 경도 58$^{\circ}$~64$^{\circ}$E(약 450Km) 및 위도 42$^{\circ}$~44$^{\circ}$S(약 200km)에서 각각 나타났다. 이것은 해저지형과 관련된 강한 와동류의 형성 때문이다. 전체적으로 볼 때 와동류 발생지역은 아규라스반류(Agulhas Return Current) 및 남극순환해류(Antarctic Circumpolar Current)와 관련하여 강한 흐름이 형성되는 지역에서 발생했다. 그리고 복수위성자료는 단수위성자료에 비해서 만족스럽게 표층순환과 해수면변동 특성을 잘 나타내었다.

• 대한원격탐사학회지
• /
• 제19권4호
• /
• pp.271-276
• /
• 2003

복합위성자료 신호처리기법을 사용해서 남인도양 지역을 중심으로 한 해수면변화와 사행 (meandering)을 연구하였다. 해수면변화는 아프리카 남부(46$^{\circ}$E)에서 크호제트 대지(Crozet basin)의 35$^{\circ}$~46$^{\circ}$S대를 걸쳐서 암스테르담-케르겔른 경로(Amsterdam-Kerguelen Passage)까지 확장된다. 이때 가장 강한 해수면변화(20~30cm)가 2개의 좁은 지역에서 발생하는데, 하나는 경도 49$^{\circ}$~57$^{\circ}$E(약 700Km) 및 위도 38$^{\circ}$~42$^{\circ}$S(약 450Km)나타났고 그리고 나머지 하나는 경도 58$^{\circ}$~64$^{\circ}$E(약 450Km) 및 위도 42$^{\circ}$~44$^{\circ}$S(약 200Km)에서 각각 나타났다. 이것은 해저지형과 관련된 강한 와동류의 형성 때문이다. 와동류 발생지역은 아규라스반류(Agulhas Return Current) 및 남극순환해류(Antarctic Circumpolar Current)와 관련하여 강한 흐름이 형성되는 지역에서 발생했다. 이때 복합위성자료(Topex/Poseidon, ERS1)는 표층순환과 해수면변동 특성을 잘 나타내었다.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
• /
• pp.922-925
• /
• 2006

The objective of this study is first to resolve the spatial and seasonal variability of BL in the bay using 'the most comprehensive' data set available for the bay and then to understand the formation mechanisms and variability in the light of the known dynamical and thermodynamical processes. The most recent study [Masson et al., 2002] on the BL variability in the bay was based on the World Ocean Atlas (WOA98) of Levitus [1998]. The temperature and salinity profiles in the bay have increased considerably after the release of WOA98. The WOA98, itself has been updated to WOA01 in 2001. Further, the deployment of ARGO profiling floats in the bay since 2002 has generated many additional profiles. In addition to the ARGO data and the updated WOA01, the hydrographic data collected from the bay under several Indian national programs and archived in the Indian Oceanographic Data Centre (IODC) was also considered in the present study. The WOA98 and WOA01 consist of only limited data from the IODC archive, especially from the Exclusive Economic Zone of India. Therefore, the combination of these data from the three different sources (WOA01, ARGO and IODC) provides ‘the most comprehensive data set’ for the bay to resolve the BLT structure and its variability in a much better scale than in the past.

• Ocean Systems Engineering
• /
• 제3권2호
• /
• pp.137-147
• /
• 2013

Moonpools are vertical wells in a floating body used onboard many types of vessels like cable-laying vessels and offshore support vessels. Moonpool gives passage to underwater activities for different types of ships as per their mission requirements. It is observed that inside a moonpool considerable relative motions may occur, depending on shape, depth of the moonpool and on the frequency range of the waves to which the ship is exposed. The vessel responses are entirely different in zero and non-zero Froude number. Former situation is paid attention in this study as the mission requirement of the platform is to be in the particular location for long period of operation. It is well known that there are two modes of responses depending on the shape of the moonpool viz., piston mode for square shape and sloshing mode for rectangular shapes with different aspect ratios of opening like 1:1.5 and 1:2 ratios. Circular shaped moonpool is also tested for measuring the responses. The vessel moored using heavy lines are modeled and tested in the wave basin. The moored lines are provided with pre-tension and the dynamic tensions on the lines are measured. The different modes of oscillations of water column are measured using wave gauge and the vessel response at a particular situation is determined. RAOs determined for various situations provide better insight to the designer. The experiments done in the wave basin may also be compared with a software package meant for handling moored floating bodies.

• 한국해양학회지:바다
• /
• 제25권1호
• /
• pp.1-8
• /
• 2020

마이오세 후기(약 6.7 Ma)에 나타난 생물기원 오팔 함량의 폭감(biogenic opal crash)이 안다만해에서 획득된 IODP Site U1447과 NGHP Site 17의 코아 퇴적층에서 확인되었다. 두 코아 사이의 오팔 함량과 전반적인 변화 경향에서 나타난 차이점은 실험분석에 사용된 시약의 농도와 층서 설정에 의해 계산된 퇴적률의 차이 때문이다. 안다만해에서 발생한 마이오세 후기 생물기원 오팔 함량의 폭감은 인도네시아 관통류(Indonesian Throughflow)의 차단으로 인한 서태평양으로부터의 영양염 공급 감소와 더불어 인도여름몬순의 약화에 의한 강수량 감소로 강물에 의한 영양염 공급 감소의 복합적인 요인에 의한 것으로 제안된다.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
• /
• pp.285-288
• /
• 2008

We analyzed evaporation data in the Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations (J-OFURO) Ver.2. There exists huge evaporation in Gulf Stream, Kuroshio Extension, the ocean dessert and the southern part of the Indian Ocean. The temporal variation of evaporation is overwhelmingly large, of which the standard deviation is more than 120(mm), in the Kuroshio Extension region. Also, the result of harmonic analysis gives that this large variation is closely related to annual variation. In addition, the first EOF mode shows long-term variation showing the maximum amplitude between 1992 and 1994 and remarkable decrease after 1994, and large amplitude in the equatorial region and northeast of Australia. The second and third modes were strongly influenced by El Nino. Moreover, we compared J-OFURO2 evaporation product with other products. We used six kinds of data sets (HOAPS3 and GSSTF2 of satellite data, NRA1, NRA2, ERA40 and JRA25 of reanalysis data) for comparison. Most products show underestimation in the most regions, in particular, in the northern North Pacific, mid-latitudes of the eastern South Pacific, and high-latitudes of the South Pacific compared with J-OFUR02. On the other hand, JRA25 and NRA2 show large overestimation in the equatorial regions. RMS difference between NRA2 and J-OFURO2 in the Kuroshio Extension was significantly large, more than 120(mm).

• Ocean and Polar Research
• /
• 제25권1호
• /
• pp.75-87
• /
• 2003

The water balance calculation in the IRL shows that fresh groundwater discharge is the primary factor, with surface runoff from gaged and ungaged areas as the second freshwater contributor. Precipitation and evaporation are almost in balance fer the entire IRL. Due to high freshwater discharge from ground-water, the annual net flow is outward from the IRL to the continental shelf of the Atlantic Ocean resulting in a relatively short flushing time, denoted as $T_{0.5}$ (50% flushing time) and $T_{0.99}$ (99% flushing time). $T_{0.5}$, and. $T_{0.99}$ without a tidal effect in the Northern IRL are 17 and 114 days, respectively, during the dry season. During the wet season, they are 10 and 65 days, respectively. Tidal flushing effects are considered in central IRL due to the proximity to Sebastian Inlet. In the Northern Central zone during dry season, $T_{0.5}$, and. $T_{0.99}$ are 6 and 43 days, respectively and during the wet season 5 and 33 days. In the Southern Central zone they are 2 and 16 days for the dry season,2 and 15 days for the wet season. High groundwater seepage into the IRL is considered to be a positive effect in maintaining relatively good water quality condition even with few narrow inlets.

• Fisheries and Aquatic Sciences
• /
• 제27권1호
• /
• pp.48-55
• /
• 2024

The study assessed the utility of mitochondrial DNA for identifying a deceased rorqual discovered off the western coast of India. Both the COI and Cytb genes exhibited remarkable 99-100% similarity with the GenBank sequence of Balaenoptera musculus through a global BLAST search, confirming their affiliation with this species. Inter-species genetic distances for COI and Cytb genes ranged from 6.75% to 9.80% and 7.37% to 10.96% respectively, compared with other Balaenopteridae species. The Bayesian phylogenies constructed based on both COI and Cytb genes demonstrated clear and separate clustering for all Balaenopteridae species, further reaffirming their distinctiveness, while concurrently revealing a cohesive clustering pattern of the generated sequences within the B. musculus clade. Beyond species confirmation, this study provides valuable insights into the presence of live and deceased B. musculus individuals within Indian marine ecosystems. This information holds significant potential for guiding conservation efforts aimed at safeguarding Important Marine Mammal Areas (IMMAs) in India over the long term.

• Journal of Advanced Research in Ocean Engineering
• /
• 제4권3호
• /
• pp.124-134
• /
• 2018

In this study, when the stability of the structure against the ocean wave is considered for designing the offshore structures in the Pacific, Indian ocean and Atlantic regions where the cyclone is largely generated, the ocean wave caused by the cyclone as well as the storm surge which called wind induced wave shall be predicted accurately for the purpose of judgment. The predicted wind induced wave was evaluated by comparing the outcome results the model test of Nobuhiro Matsunaga (1996) and Conventional Experiment forms such as Jonswap spectral forms(Carter, 1982), Simplified Donelan / Jonswap forms(Wilson 1965), Donelan spectral forms(Donelan 1980), Revised SPM forms(Schafer Lake 2005, 2007, 2008), SPM forms(CERC 1977), the CEM forms(Kazeminezhad et al., 2005), SMB forms(Sverdrup Munk and Bretschneider 1947,1954, 1970), and Revised Wilson forms(Wilson 1965, Goda 2003). Most of these conventional experiment forms confirmed a good match when the fetch length is less than 10 km. However, normal cyclone fetch length is more than 100km, With this fetch length, the comparison result is 10.4% of deviation when used Jonswap spectral forms(Carter, 1982) but the deviation of the other forms is around 74% due to boundary limit of fetch and wind duration. Therefore, in this study, we proposed the revised forms after comparing these results with the model results. We confirmed that the deviation range is around 10% based on revisited experiment forms. Since the model test was carried out in the small water tank, the scale up factor was applied to the mode test results in order to obtain similar results to the actual environment from revisited forms.

• Ocean Systems Engineering
• /
• 제1권4호
• /
• pp.285-296
• /
• 2011

Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. The main objective of this paper is to present the response analysis of the slack moored spar platform supporting 5MW wind turbine with bottom keel plates in regular and random waves, studied experimentally and numerically. A 1:100 scale model of the spar with sparD, sparCD and sparSD configuration was studied in the wave basin ($30{\times}30{\times}3m$) in Ocean engineering department in IIT Madras. In present study the effect of wind loading, blade dynamics and control, and tower elasticity are not considered. This paper presents the details of the studies carried out on a 16 m diameter and 100 m long spar buoy supporting a 90 m tall 5 MW wind turbine with 3600 kN weight of Nacelle and Rotor and 3500 kN weight of tower. The weight of the ballast and the draft of the spar are adjusted in such a way to keep the centre of gravity below the centre of buoyancy. The mooring lines are divided into four groups, each of which has four lines. The studies were carried out in regular and random waves. The operational significant wave height of 2.5 m and 10 s wave period and survival significant wave height of 6 m and 18 s wave period in 300 m water depth are considered. The wind speed corresponding to the operational wave height is about 22 knots and this wind speed is considered to be operating wind speed for turbines. The heave and surge accelerations at the top of spar platform were measured and are used for calculating the response. The geometric modeling of spar was carried out using Multisurf and this was directly exported to WAMIT for subsequent hydrodynamic and mooring system analysis. The numerical results were compared with experimental results and the comparison was found to be good. Parametric study was carried out to find out the effect of shape, size and spacing of keel plate and from the results obtained from present work ,it is recommended to use circular keel plate instead of square plate.