• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.599-607
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• 2015

The purpose of this study is to reproduce long-term wave fields in coastal waters of Korea based on wave hind-casting modelling and discuss its applications. To validate wind data(NCEP, ECMWF, JMA-MSM), comparison of wind data was done with wave buoy data. JMA-MSM predicted wind data with high accuracy. But due to relatively longer period of ECMWF wind data as compared to that of JMA-MSM, wind data set of ECMWF(2001~2014) was used to perform wave hind-casting modelling. Results from numerical modelling were verified with the observed data of wave buoys installed by Korea Meteorological Administration(KMA) and Korea Hydrographic and Oceanographic Agency(KHOA) on offshore waters. The results agree well with observations at buoy stations, especially during the event periods such as a typhoon. Consequently, the wave data reproduced by wave hind-casting modelling was used to obtain missing data in wave observation buoys. The obtained missing data indicated underestimation of maximum wave height during the event period at some points of buoys. Reasons for such underestimation may be due to larger time interval and resolution of the input wind data, water depth and grid size etc. The methodology used in present study can be used to analyze coastal erosion data in conjunction with a wave characteristic of the event period in coastal areas. Additionally, the method can be used in the coastal disaster vulnerability assessment to generate wave points of interest.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.228-237
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• 2015

Field observations were conducted to collect hydrodynamic and morphological data, which are needed to account for mechanisms of bathymetry changes caused by physical forcings, in Haeundae beach. In order to quantitatively describe characteristics of wave transformations and current patterns in space in winter and summer, in-situ sensors for measuring waves and current profiles were installed at three locations in the cross-shore direction and also three locations in the along-shore direction. As for the results of wave measurements, waves with main direction from the east dominate in winter while waves are incident from the S and the ESE in summer. Analysis of current data reveals that currents over the study domain are considerably influenced by a pattern of tidal motions, thereby, mainly oscillating in the direction of tidal currents, i.e., east-west directions, in both winter and summer. Currents tend to be influenced by local bathymetry in the shallow water region, with the direction changed along the depth contours and the magnitude reduced as they approach the shoreline. The results analysed from the hydrodynamic data through this study can be further combined with the morphological and bathymetry data, leading to the quantification of seasonal sediment transport rates and sand budget changes.

• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.479-484
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• 2007

For calculation of wave field for design of coastal and port structures, generally the wind fields from inland observation record or the predicted waves from deep water wave transformation model are being used. However, for the first case, as we should revise the wave data adopting correcting parameters depending on the distance from the coast and location, it is difficult to extract water waves from wind field. Furthermore, for the second case, because of the calculation which executed under very large grid sizes in the wide domain, the simulation(wave transformation) implied uncertainty in the near shore area and shallow region. So it's difficult to obtain exact data from the simulation. Thus, in this study the calculation of wave field on shallow water is accomplished using the observed data of typhoon 'Maemi' in the Korea Eastern South sea. Moreover, for the accuracy of the calculated wave field, we compared and studied the observed data of wave height and direction on the vicinity of the Ulsan waters. It is proved that the results of this study is more accurate than the existing method with showing ${\pm}1.3%$ difference between observed and calculated wave height distribution in Ulsan waters

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.29-36
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• 2005

The crustal structure of Korean Peninsula is investigated by analyzing phase velocity dispersion data of Rayleigh wave. Earthquakes recorded by three component seismographs during 1999 - 2004 in South Korea are used in this study. The fundamental mode signals of Rayleigh waves are obtained from vertical components of seismograms by multiple filter technique method and phase match filter method. Velocity dispersion curves of surface waves for 14 propagation paths on the great circle are computed from the fundamental mode signals on the great circle path by two-station method. Treating the shear velocity of each layer as an independent parameter, phase velocities of Rayleigh wave are inverted. The result models are regarded as average structure for surface wave propagation paths respectively. All the results can be explained by an earth model of the Korean Peninsula comprising crust of shear-wave velocity increasing from 2.8 to 3.25 km/sec from top to 33 km depth and uppermost mantle of shear-wave velocity between 4.55 and 4.67 km/sec.

• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.234-239
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• 2013

The $M_W$ 9.0 thrust-fault earthquake has occurred in the Pacific coast of Tohoku, Japan, on March 11, 2011. We present the detection of the great earthquake and analyze T-waves associated with the main event and two other big aftershocks ($M_W$ > 7) recorded in a hydroacoustic array (H11N) in the Pacific Ocean by performing array and spectral analysis to examine characteristics of T-waves generated from the big events. The complex rupture process of the main event directly influences on the shape of the T-waves, and the peak locates on where T-waves excited from fast rupturing process arrive. We compare the two aftershocks with different fault type and show that the fault type and the source depth change shape and spectral contents of T-waves.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.127-128
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• 2007

파랑이 외해로부터 연안으로 내습하면서 발생되는 파랑 변형, 즉, 굴절, 회절, 천수 그리고 쇄파 동에 의한 변형을 일으킨다. 이러한 파랑변형을 일으키는 주된 물리적 인자는 수심의 변화이지만 태풍과 같은 강한 바람이 부는 해역에서는 바람인자를 반드시 고려해야만 한다. 본 연구에서는 바람효과가 고려된, 에너지 스펙트럼 모형 (SWAN; Simulating WAve Nearshore) 을 이용한 수치실험을 수행하였다. 그리고 해석해 및 Karlsson 모형에 대한 수치 해와 비교를 통해 모델의 검증을 실시하였다. 또한 부산항 설 해역을 대상으로 태풍 매미 내습 시 입사 파랑 조건을 적용하였으며 실제 관측 치와 바람효과의 유무에 따른 수치 계산치를 비교한 결과, 바람효과를 고려한 계산결과가 실제 관측치와의 양호한 일치를 나타내었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2146-2150
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• 2008

본 연구에서는 용기포항 동방파제 건설이 사곶 수욕장에 미치는 영향을 평판재하시험, 토질분석시험, 위성사진 자료 분석, 파랑, 조류, 수심 등의 현장관측과 파랑, 파랑류, 조류, 그리고 퇴적물 이동 등에 대한 수치모형을 통하여 사곶해수욕장의 동역학적 특성을 파악하였다. 평판재하시험과 토질분석시험 결과 기존의 사곶해수욕장 지역의 지지력 변화는 거의 없는 것으로 나타났으며, 방파제 건설로 인해 퇴적이 진행 중인 지역은 상대적으로 지지력이 낮게 나타났다. 현장관측으로 수집된 파랑, 조류, 수심의 자료는 수치모형의 입력 값으로 사용되었으며, 파랑류 수치모형결과 사곶 해수욕장 부근에서 파향에 따라 약한 소규모 와류가 발생하였으며, 퇴적물이동 수치모형의 경우 국소 와류에 의한 지형변화가 발생하였으며, 남서와 북동에 약간의 퇴적이 발생하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.135-145
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• 2020

Wave observation is widely used to direct observation method for observing the water surface elevation using wave buoy or pressure gauge and remote-sensing wave observation method. The wave buoy and pressure gauge can produce high-quality wave data but have disadvantages of the high risk of damage and loss of the instrument, and high maintenance cost in the offshore area. On the other hand, remote observation method such as radar is easy to maintain by installing the equipment on the land, but the accuracy is somewhat lower than the direct observation method. This study investigates the data quality of MIROS Wave and Current Radar (MWR) installed at Dokdo and improve the data quality of remote wave observation data using the wave buoy (CWB) observation data operated by the Korea Meteorological Administration. We applied and developed the three types of wave data quality control; 1) the combined use (Optimal Filter) of the filter designed by MIROS (Reduce Noise Frequency, Phillips Check, Energy Level Check), 2) Spike Test Algorithm (Spike Test) developed by OOI (Ocean Observatories Initiative) and 3) a new filter (H-Ts QC) using the significant wave height-period relationship. As a result, the wave observation data of MWR using three quality control have some reliability about the significant wave height. On the other hand, there are still some errors in the significant wave period, so improvements are required. Also, since the wave observation data of MWR is different somewhat from the CWB data in high waves of over 3 m, further research such as collection and analysis of long-term remote wave observation data and filter development is necessary.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.357-362
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• 2012

Despite the Wave observations data is very important information to human life at sea, the technology development and research for wave equipments are lacking. In this study, the wave observation system using GPS was evaluated the quality of wave observation data by comparing of long-term observations. The result of the comparison of the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000), the correlation coefficient of the significant wave height and significant wave periods is 0.997 and 0.990 respectively. Also in case of BIAS, the significant wave height is 0.014 m, the significant wave period is -0.212 sec. It makes no significant differences whether the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000). These results of the wave observation data using GPS quality will be evaluated as very good.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.771-780
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• 2014

We installed HF Radar of Array type in Site A and Site B, observing the real-time wave and current in the central East coast of Korea. WERA(WavE RAdar) in this research uses HF Radar of Array Type with frequency range of 24.525 MHz, developed by Helzel, Germany. Each site is a 8-Channel system consisting of four transmitters and eight receivers, generating wave and current data, being observed every thirty minutes at the present time. HF Radar has grid resolution of an interval of 1.5 km using bandwidth of 150 kHz; The wave data covers an observation range of about 25 km, and the current data covers the maximum observation range of about 50 km. The Wave data observed by HF Radar was compared and verified with the AWAC data observed in the research sites. MIT also compared the Current data observed by HF Radar with Monthly the East sea average surface current and current flow pattern provided by KOHA(Korea Hydrographic and oceanographic Administration). The regression line and deviation of the comparison data of Wave was calculated by Principal Component Analysis, which showed correlation coefficient 0.86 and RMSD 0.186. Besides, data analysis of long-term changes of the current in the East coast showed that, during August and September, the North Korean Cold Current flow into the southward direction and the East Korean Warm Current flow into the northward direction in the coast.