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Yanggu, South Korea

Byun D.-S.,Ocean Research Division | Hart D.E.,University of Canterbury | Jeong W.-J.,Korea Hydrographic and Oceanographic Administration
Energies | Year: 2013

In this study we estimate the prospective tidal current energy resources off the south and west coasts of Korea and explore the influence of modeling tidal current energies based on 15-day versus month-long data records for regimes with pronounced perigean/apogean influences. The tidal current energy resources off southern and western Korea were calculated using 29-day in situ observation data from 264 stations. The resultant annual energy densities found at each station were categorized into six groups, with a greater percentage of sites falling into the lower-energy groups: 1.1% for >10 MWh·m-2; 2.7% for 5 to 10 MWh·m-2; 6.8% for 3 to 5 MWh·m-2; 9.1% for 2 to 3 MWh·m-2 and 80.3% for <2 MWh·m-2. Analysis shows that the greatest concentration of high annual energy densities occurs in the Jeonnam Province coastal region on the western tip of southwest Korea: 23 MWh·m-2 at Uldolmok, 15 MWh·m-2 at Maenggol Sudo, 9.2 MWh·m-2 at Geocha Sudo and 8.8 MWh·m-2 at Jaingjuk Sudo. The second highest annual energy density concentration, with 16 MWh·m-2, was found in Gyudong Suro, in Gyeonggi Province's Gyeonggi Bay. We then used data from the 264 stations to examine the effect of perigean and apogean influences on tidal current energy density evaluations. Compared to derivations using month-long records, mean annual energy densities derived using 15-day perigean spring-neap current records alone overestimate the annual mean energy by around 10% whereas those derived using only the apogean records underestimate energy by around 12%. In particular, accuracy of the S2 contribution to the energy density calculations is significantly affected by use of the 15-day data sets, compared to the M2 component, which is relatively consistent. Further, annual energy density estimates derived from 29-day records but excluding the N2 constituent underestimate the potential resource by about 5.4%. Results indicate that one month of data is required to accurately estimate tidal current energy in regimes showing pronounced perigean and apogean differences in spring-neap tidal current patterns and that inclusion of the N2 constituent in calculations is preferable. This finding has widespread applicability for green energy resource assessments, for example, in regions of the Unites States Atlantic coast and in New Zealand. © 2013 by the authors. Source


Jung K.Y.,Ocean Research Division | Ro Y.J.,Chungnam National University | Choi Y.H.,Southwest Research Institute | Kim B.J.,Chungnam National University
Marine Pollution Bulletin | Year: 2015

We investigated bottom-water hypoxia induced by freshwater discharge from two artificial dykes into Chunsu Bay (CSB), Korea, during the summer of 2010. Field observations and model results of the dynamic and water-quality parameters indicated that the triggering mechanism of the hypoxia was strong stratification formed by the freshwater discharge from both dykes, which limited the dissolved oxygen (DO) supply in bottom water. Beneath the pycnocline, DO was consumed by sediment oxygen demand (SOD) during the summer. To investigate these processes, model experiments were conducted using a simplified DO budget model coupled with a 3D hydrodynamic model. The DO concentration in the northern part of CSB reached hypoxic conditions very quickly after 3.4. days of discharge and lasted 18. days until normal conditions resumed. In sum, in the CSB, marked stratification and its maintenance played a critical role in hypoxia in bottom water. © 2015 Elsevier Ltd. Source


Oh K.-H.,Korea Advanced Institute of Science and Technology | Lee S.,Korea Advanced Institute of Science and Technology | Song K.-M.,Korea Advanced Institute of Science and Technology | Lie H.-J.,Korea Advanced Institute of Science and Technology | Kim Y.-T.,Ocean Research Division
Acta Oceanologica Sinica | Year: 2013

The Yellow Sea Cold Water Mass (YSCWM) is one of the important water mass in the Yellow Sea (YS). It is distributed in the lower layer in the Yellow Sea central trough with the temperature less than 10.C and the salinity lower than 33.0. To understand the variability of the YSCWM, the hydrographic data obtained in April and August during 2009.2011 are analyzed in the southeastern Yellow Sea. In August 2011, relatively warm and saline water compared with that in 2009 and 2010 was detected in the lower layer in the Yellow Sea central area. Although the typhoon passed before the cruise, the salinity in the Yellow Sea central trough is much higher than the previous season. It means that the saline event cannot be explained by the typhoon but only by the intrusion of saline water during the previous winter. In April 2011, actually, warmand saline water (T >10.C, S >34) was observed in the deepest water depth of the southeastern area of the Yellow Sea. The wind data show that the northerly wind in 2011 winter is stronger than in 2009 and 2010 winter season. The strong northerlywind can trigger the intrusion ofwarmand saline Yellow Sea Warm Current. Therefore, it is proposed that the strong northerly wind in winter season leads to the intrusion of the Yellow Sea Warm Current into the Yellow Sea central trough and influenced a variability of the YSCW Min summer. © 2013 The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg. Source


Byun D.-S.,Ocean Research Division
Ocean and Polar Research | Year: 2011

This is a preliminary study of the feasibility of obtaining reliable tidal current harmonic constants, using one month of current observations, to verify the accuracy of a tidal model. An inference method is commonly used to separate out the tidal harmonic constituents when the available data spans less than a synodic period. In contrast to tidal constituents, studies of the separation of tidal-current harmonics are rare, basically due to a dearth of the long-term observation data needed for such experiments. We conducted concurrent and monthly harmonic analyses for tidal current velocities and heights, using 2 years (2006 and 2007) of current and sea-level records obtained from the Tidal Current Signal Station located in the narrow waterway in front of Incheon Lock, Korea. Firstly, the l-year harmonic analyses showed that, with the exception of M 2 and S 2 semidiurnal constituents, the major constituents were different for the tidal currents and heights. K 1, for instance, was found to be the 4th major tidal constituent but not an important tidal current constituent. Secondly, we examined monthly variation in the amplitudes and phase-lags of the S 2 and K 1 current-velocity and tide constituents over a 23-month period. The resultant patterns of variation in the amplitudes and phase-lags of the S 2 tidal currents and tides were similar, exhibiting a sine curve form with a 6-month period. Similarly, variation in the K 1 tidal constant and tidal current-velocity phase lags showed a sine curve pattern with a 6-month period. However, that of the K 1 tidal current-velocity amplitude showed a somewhat irregular sine curve pattern. Lastly, we investigated and tested the inference methods available for separating the K 2 and S 2 current-velocity constituents via monthly harmonic analysis. We compared the effects of reduction in monthly variability in tidal harmonic constants of the S 2 currentvelocity constituent using three different inference methods and that of Schureman (1976). Specifically, to separate out the two constituents (S 2 and K 2), we used three different inference parameter (i.e. amplitude ratio and phase-lag diggerence) values derived from the 1-year harmonic analyses of current-velocities and tidal heights at (near) the short-term observation station and from tidal potential (TP), together with Schureman's (1976) inference (SI). Results from these four different methods reveal that TP and SI are satisfactorily applicable where results of long-term harmonic analysis are not available. We also discussed how to further reduce the monthly variability in S 2 tidal current-velocity constants. Source


Park S.-Y.,Ocean Research Division | Byun D.-S.,Ocean Research Division | Hart D.E.,University of Canterbury
Ocean Science Journal | Year: 2012

This paper provides an explanation of an automated solution for correctly interpolating phase-lags across abrupt boundaries. Although an automated solution to this problem has existed for several years, this is not commonly known and so many researchers continue to perform corrections manually. Interpolation errors commonly occur when tidal propagation surfaces are generated for regimes with amphidromic points. General correction methods are manual, clunky and prone to operator error. The problem can be solved by applying a simple method to scalarize the phase-lag vectors pre-interpolation. This approach successfully and automatically generates correct tidal phase-lag interpolation values and may be applied to any surface mapping software used to interpolate phase-lags. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht. Source

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