• 제목/요약/키워드: Ocean drifter

검색결과 27건 처리시간 0.022초

순환신경망을 이용한 뜰개의 관측 데이터 보정 (Correction of Drifter Data Using Recurrent Neural Networks)

  • 김경도;김용혁
    • 한국융합학회논문지
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    • 제9권3호
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    • pp.15-21
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    • 2018
  • 해양 뜰개는 해수면을 떠다니며 해양 기상 등을 관측하는 장비로, 뜰개를 통해 관측한 데이터는 해양 기상 예측, 유류유출 예측 등의 상황에서 활용된다. 관측 데이터는 관측 시에 오측(error data) 또는 결측(missing data)이 발생할 수 있으며, 오측 또는 결측된 데이터가 포함 될 경우, 데이터를 사용하는 모델들의 정확도가 떨어질 수 있다. 본 논문에서는 데이터 보정을 위한 방법으로 순환신경망을 이용한 데이터 보정 모델을 제안한다. 2015년 7개, 2016년 8개의 뜰개를 통해 수집한 해양 데이터를 이용한 보정 실험 결과와 보정 결과를 검증하기 위한 뜰개 이동 예측 실험을 설명하며, 실험 결과, 데이터 보정을 통해 13.9%의 데이터가 보정되었으며, 이동 예측 모델의 성능이 1.4% 향상되는 것을 보였다.

Potential of Argo Drifters for Estimating Biological Production within the Water Column

  • Son, Seung-Hyun;Boss, Emmanuel;Noh, Jae-Hoon
    • Ocean Science Journal
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    • 제41권2호
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    • pp.121-124
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    • 2006
  • Argo drifters provide information of the vertical structure in the water column and have a potential for the improvement of understanding phytoplankton primary production and biogeochemical cycles in combination with ocean color satellite data, which can obtain the horizontal distribution of phytoplankton biomass in the surface layer. Our examples show that using Argo drifters with satellite-measured horizontal distribution of phytoplankton biomass at the sea surface allow an improved understanding of the development of the spring bloom. The other possible uses of Argo drifter are discussed.

GPS 뜰개를 이용한 해양 표면류 관측 (Observation of the Sea Surface Skin Current Using a GPS-Drifter)

  • 박준성;강기룡;이석;이상룡
    • Ocean and Polar Research
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    • 제35권3호
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    • pp.193-203
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    • 2013
  • A GPS-drifter was newly designed to observe the sea surface skin current and to estimate the direct wind effect on the sea surface. After conducting a test to establish and verify the accuracy of the GPS itself in the laboratory, in-situ experimental campaigns at Saemangeum in Gunsan city and Haeundae in Busan city, Korea, were carried out to ascertain the drifter track and to estimate the velocity data set on Oct. 3, 15, 23, 27 and Nov. 25, 2011. The current meters, RCM9 and ADCP, were moored together to remove the background current field, and the wind data were obtained from several marine stations such as towers and buoys in these areas. The drifter-observed velocity show good agreement with the flow obtained by the HF radar in the Saemangeum area. The direction of the wind-driven current extracted from the drifter-observed velocity was completely deflected to the right, however the degree of the angle was different according to the drift types. The average speed of the wind-driven current matched with 2.19~2.81% of the wind speed and the deflection angle was about $8.0{\sim}10.9^{\circ}$ without adjustment for the land-sea effect, and about 2.19~2.84% and $4.1{\sim}6.0^{\circ}$ with the adjustment for the land-sea effect.

An Estimation of Tidal Currents from Satellite-tracked Drifters and its Application to the Yellow Sea

  • Lee, Se-Ok;Cho, CHeol-Ho;Kang, Sok-Kuh;Lie, Heung-Jae
    • Journal of the korean society of oceanography
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    • 제35권2호
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    • pp.65-77
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    • 2000
  • A simple but effective method has been developed for estimating diurnal and semi-diurnal tidal currents from trajectories of satellite-tracked drifters. The estimation method consists of separation of tidal current signals contained in the drifter trajectories, computation of undulations by diurnal and semi-diurnal currents, and correction of dominant diurnal and semi-diurnal tidal constituents. M$_2$ tidal currents estimated from drifter trajectories in the Yellow Sea are well consistent with those observed by moored current meters and this supports the validity of this method. We have constructed M$_2$ tidal current chart in the Yellow Sea by applying this method to available drifter trajectories collected during 1994-1998. According to this chart, M$_2$ current in the Yellow Sea rotates in the clockwise direction south of 35$^{\circ}$ 30'N but in the counterclockwise one to the north. Also it is found that the M$_2$ current is strong in the bank area northeast of the Changjiang River mouth and in the Korean coastal area, while it is weak in the deep central trough.

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고해상도 기후예측시스템의 표층해류 예측성능 평가 (Assessment of Ocean Surface Current Forecasts from High Resolution Global Seasonal Forecast System version 5)

  • 이효미;장필훈;강기룡;강현석;김윤재
    • Ocean and Polar Research
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    • 제40권3호
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    • pp.99-114
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    • 2018
  • In the present study, we assess the GloSea5 (Global Seasonal Forecasting System version 5) near-surface ocean current forecasts using globally observed surface drifter dataset. Annual mean surface current fields at 0-day forecast lead time are quite consistent with drifter-derived velocity fields, and low values of root mean square (RMS) errors distributes in global oceans, except for regions of high variability, such as the Antarctic Circumpolar Current, Kuroshio, and Gulf Stream. Moreover a comparison with the global high-resolution forecasting system, HYCOM (Hybrid Coordinate Ocean Model), signifies that GloSea5 performs well in terms of short-range surface-current forecasts. Predictions from 0-day to 4-week lead time are also validated for the global ocean and regions covering the main ocean basins. In general, the Indian Ocean and tropical regions yield relatively high RMS errors against all forecast lead times, whilst the Pacific and Atlantic Oceans show low values. RMS errors against forecast lead time ranging from 0-day to 4-week reveal the largest increase rate between 0-day and 1-week lead time in all regions. Correlation against forecast lead time also reveals similar results. In addition, a strong westward bias of about $0.2m\;s^{-1}$ is found along the Equator in the western Pacific on the initial forecast day, and it extends toward the Equator of the eastern Pacific as the lead time increases.

Comparisons of Ocean Currents Observed from Drifters and TP/ERS in the East Sea

  • Lee, Dong-Kyu;Niiler, Pearn P.;Suk, Moon-Sik
    • Ocean and Polar Research
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    • 제23권2호
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    • pp.133-139
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    • 2001
  • Ocean currents estimated from sea height anomalies derived from inter-calibrated TP/ERS are compared with daily mean currents measured with satellite-tracked drifters. The correlation coefficient between the geostrophic current from TP/ERS and surface current at 15 m depth from drifter tracks was found to be about 0.5. Due to the limitation of satellite ground tracks, small scale eddies less than 80 km are poorly resolved from TP/ERS. One of the interesting results of this study is that coastal currents along the eastern coast of Korea were well reproduced from sea height anomalies when the coastal currents were developed in association with eddies near the South Korean coast. The eddy kinetic energy (EKE) estimated from drifters, TP/ERS, and a numerical model are also compared. The EKE estimated from drifters was about 22 % higher than EKE calculated from TP/ERS. The pattern of low EKE level in the northern basin and high EKE level in the southern East Sea is shown in the EKE estimates derived from both the drifters and TP/ERS.

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뜰개 이동 예측을 위한 신경망 및 통계 기반 기계학습 기법의 성능 비교 (Performance Comparison of Machine Learning Based on Neural Networks and Statistical Methods for Prediction of Drifter Movement)

  • 이찬재;김경도;김용혁
    • 한국융합학회논문지
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    • 제8권10호
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    • pp.45-52
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    • 2017
  • 뜰개는 해양에서 해수의 특성 및 흐름을 관측하기 위한 장비로서, 해수의 흐름 관측을 이용해 유출유 확산 예측을 위해 사용될 수 있다. 본 논문에서는 관측기관에서 사용하는 뜰개가 특정 시간 간격으로 관측한 바람 및 해수의 특성과 이동경로를 기계학습 기법들을 이용하여 학습시키고 예측하는 모델을 제안한다. 서포트벡터 회귀, 방사기저함수 네트워크, 가우시안 프로세스, 다층 퍼셉트론, 순환신경망을 이용하여 뜰개의 이동경로 예측 방법을 제시한다. 기존 MOHID 수치모델과 비교하여 각 기법별로 4 개의 사례중 3 개에서 성능이 개선되었으며, 가장 좋은 개선율을 보인 기법은 LSTM으로 평균 47.59% 개선되었다. 추후 연구에서는 배깅과 부스팅을 이용하여 가중치를 부여하여 정확도를 개선할 예정이다.

Some High-Frequency Variability of Currents Obtained by "GeoDrifters" in the Tsushima Current Region

  • Seung, Young Ho;Park, Jong Jin;Kwon, Young-Yeon;Kim, Sung-Joon;Kim, Hong-Sun;Park, Yong-Chul
    • Ocean and Polar Research
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    • 제39권3호
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    • pp.169-179
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    • 2017
  • The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

Validation of OpenDrift-Based Drifter Trajectory Prediction Technique for Maritime Search and Rescue

  • Ji-Chang Kim;Dae, Hun, Yu;Jung-eun Sim;Young-Tae Son;Ki-Young Bang;Sungwon Shin
    • 한국해양공학회지
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    • 제37권4호
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    • pp.145-157
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    • 2023
  • Due to a recent increase in maritime activities in South Korea, the frequency of maritime distress is escalating and poses a significant threat to lives and property. The aim of this study was to validate a drift trajectory prediction technique to help mitigate the damages caused by maritime distress incidents. In this study, OpenDrift was verified using satellite drifter data from the Korea Hydrographic and Oceanographic Agency. OpenDrift is a Monte-Carlo-based Lagrangian trajectory modeling framework that allows for considering leeway, an important factor in predicting the movement of floating marine objects. The simulation results showed no significant differences in the performance of drift trajectory prediction when considering leeway using four evaluation methods (normalized cumulative Lagrangian separation, root mean squared error, mean absolute error, and Euclidean distance). However, leeway improved the performance in an analysis of location prediction conformance for maritime search and rescue operations. Therefore, the findings of this study suggest that it is important to consider leeway in drift trajectory prediction for effective maritime search and rescue operations. The results could help with future research on drift trajectory prediction of various floating objects, including marine debris, satellite drifters, and sea ice.

위성원격탐사를 이용한 동해 원산연안의 재발생 와동류 연구 (Study of a Recurring Anticyclonic Eddy off Wonsan Coast in Northern Korea Using Satellite Tracking Drifter, Satellite Ocean Color and Sea Surface Temperature Imagery)

  • 서영상;장이현;김정희
    • 대한원격탐사학회지
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    • 제16권3호
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    • pp.211-220
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    • 2000
  • 위성자료를 이용하여 동해북부 원산 연근해역의 재발생 와동류에 대한 형태변동, 유속, 발생기작 등을 연구하였다. 1999년 1월 4일부터 3월 18일까지의 기간에 대한 ARGOS의 표류부이 자료(위치정보 및 수온), NOAA 위성의 AVHRR 자료(표면수온) 그리고 Orbview-2 위성의 SeaWiFS 자료(클로로필 a)를 이용하여 재발생 와동류의 수평공간 규모를 파악하였다. 또한 재발생 와동류의 기작과 변동원인을 규명하고자 속초와 울릉도에서의 풍향, 풍속자료, 묵호-울릉도간 해수면 차 값 및 해저지형과 와동류에 포획되어 있는 표류부이의 시.공간적 위치변동간의 상관정도를 파악하였다. 원산 연안해역에서의 와동류의 72일간 평균유속은 153 km/h (42 cm/sec)로 분석되었다. 이 와동류는 cold core, 시계방향의 회전, 직경 110 km의 수평공간을 가진 재발생 와동류로서 와동류의 중심은 위도 $39^{\circ}N$, 경도 $129^{\circ}E$로 분석되었다.