• 한국지구과학회지
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• 제41권4호
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• pp.344-355
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• 2020

Tropical cyclone scale vortices and associated Rossby waves were investigated numerically using high-resolution barotropic models on the global domain. The equations of the barotropic model were discretized using the spectral transform method with the spherical harmonics function as orthogonal basis. The initial condition of the vortex was specified as an axisymmetric flow in the gradient wind balance, and four types of basic zonal states were employed. Vortex tracks showed similar patterns as those on the beta-plane but exhibited more eastward displacement as they moved northward. The zonal-mean flow appeared to control not only the west-east translation but also the meridional translation of the vortex. Such a meridional influence was revealed to be associated with the beta gyre and the Rossby wave, which are formed around the vortex due to the beta effect. In the case of the basic zonal state of climatological mean, the meridional translation speed reached the maximum value when the vortex underwent recurving.

• 한국해안해양공학회지
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• 제6권3호
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• pp.309-325
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• 1994

알라스카 만의 해수순환은 바람응력의 큰 계절적 변동에도 불구하고 큰 변화를 보이지 않는다. 그 역학적 원인을 알아보기 위해 일련의 수치모델 실험을 행하였다. 먼저, 관측밀도장으로부터 구한 진단모델 결과에 의하면 알라스카 난류의 계절적 변동은 거의 없으며, 여러 종류의 예보모델 결과에 의하면 해저지형과 경압성이 바람의 계절변동에 대한 해양반응에 영향을 미침을 보여준다. 모델 결과의 비교에 의해 경압해양의 바람의 계절변동에 대한 반응은 주로 순압성이며 순압 해수순환은 해저지형의 분만효과에 의해 약해지기 때문에 해수순간의 계절적 변동이 거의 나타나지 않는다.

• Ocean and Polar Research
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• 제23권2호
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• pp.195-203
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• 2001

A fine-grid (3 km ${\times}$ 3 km), three-dimensional nowcast system of sea levels, currents, temperature, and salinity is being developed for the Taiwan Strait. The project takes a balanced approach relying equally on models and observations, will have the capacity of real-time data assimilation, and is aimed at both practical and scientific applications. To determine boundary conditions and verify model results, eight coastal tide-gauge stations were first established along both sides of the strait. Strait-wide hydrographic surveys were conducted by research vessels. Currents are being measured using bottom-mounted ADCP moorings in a meridional deep channel off southwest Taiwan and along a traverse section in the central part of the strait. In addition to a fine-resolution three-dimensional model of the Taiwan Strait, an adjoint model and a larger-domain two-dimensional model were used to better determine boundary conditions in the northern and southern boundaries of the strait. In the first stage of model development, barotropic tides were successfully simulated in a hindcast mode. The protocol product has been released to general public, including government agencies, universities and general users.

• 한국지구과학회지
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• 제37권2호
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• pp.107-116
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• 2016

전구영역 수치모델을 이용하여 순압 로스비-하우어비츠 파동의 안정성을 조사하였다. 본 연구에서 조사한 로스비-하우어비츠 파동은 강체 회전하는 동서 기본류와 유한한 진폭을 가지는 구면조화 파동으로 구성된다. 로스비-하우어비츠 파동은 강체 회전하는 동서 평균류의 강도에 따라 정상 또는 비정상의 구조로 나타난다. 수치 실험을 통해 임의의 다른 두 시간에서 섭동장의 진폭을 비교하여 파동의 안정성뿐만 아니라 성장률을 결정하였다. 로스비-하우어비츠 파동의 불안정 모드는 다양한 동서 파수 성분이 결합된 형태로 나타났다. 파동의 속도가 느린 지역에서 와도 섭동장은 불연속적인 형태를 보이는데, 이는 모델의 수평 해상도와 관계가 없는 것으로 밝혀졌다. 푸리에-유한 요소 모델에서 더 이른 적분 시간에 불안정 모드가 나타났는데, 이는 구면조화 스펙트럴 모델 대비 더 낮은 수치 정확도를 가지기 때문인 것으로 보인다. 모델의 전체적인 정확도를 고려하여, 불안정 모드가 구면 조화 파동을 전체적으로 지배하기 시작하는 시간을 추정하였다.

• 대기
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• 제27권2호
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• pp.199-211
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• 2017

The cold surges over East Asia can be grouped to two types of the wave-train and the blocking. Recently, the observational study proposed new dynamical index to objectively identify cold surge types. In this study, the dynamical index is applied to the simulations of 10 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Focusing on assessment of cold surge simulation, we discuss characteristic of the wave-train and blocking cold surges in the climate models. The wave-train index (WI) and the blocking index (BI) based on potential temperature anomalies at dynamical tropopause over the subarctic region, the northeast China, and the western North Pacific enable us to classify cold surges in the climate models into two types. The climate models well simulate the occurrence mechanism of the wave-train cold surges with vertical structure related to growing baroclinic wave. However, while the wave-train in the observation propagates in west-east direction across the Eurasia Continent, most of the models simulate the southeastward propagation of the wave-train originated from the Kara Sea. For the blocking cold surges, the general features in the climate models well follow those in the observation to show the dipole pattern of a barotropic high-latitude blocking and a baroclinic coastal trough, leading to the Arctic cold surges with the strong northerly wind originated from the Arctic Sea. In both of the observation and climate models, the blocking cold surges tend to be more intense and last longer compared to the wave-train type.

• Journal of the korean society of oceanography
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• 제31권3호
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• pp.123-133
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• 1996

We describe here the shallow water tides in the seas around Korea, obtained from a nonlinear barotropic model of tides in a domain encompassing the Yellow Sea, the East China Sea and the East Sea (Sea of Japan). As expected, the shallow water tides are large in the shallow marginal areas around the Yellow Sea, with the M4 tide reaching amplitudes as high as 10 cm near the Korean coast, and quite small in the East Sea. However, we also find that the regions east of the Yangtze River ($126^{\circ}E,$ $30^{\circ}N$) in the East China Sea also sustain large shallow water tides, with $M_{4}$, amplitudes reaching 5 cm. Such large shallow water tides are an important component of altimeter-measured sea levels and should not be ignored in any altimetric analyses of the Yellow Sea and the East China Sea. This study also highlights the desirability of very high resolution models to derive accurate shallow water tides in coastal regions.

• Ocean and Polar Research
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• 제23권2호
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• pp.141-160
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• 2001

The challenge of predicting the Japanese coastal ocean motivated Frontier Observational Research System for Global Change (FORSGC) and the Japan Marine Science and Technology Center (JAMSTEC) to start a multiyear observational programme in the upstream Kuroshio in November 2000. This field effort, the Kuroshio Observation Program (KOP), should enable us to determine the barotropic and baroclinic components of the western boundary current system, thus, to better understand interactions of the currents with mesoscale eddies, the Kuroshio instabilities, and path bimodality. We, then, will be able to improve modeling predictability of the mesoscale, seasonal, and inter-annual processes in the midstream Kuroshio near the Japanese main islands by using this knowledge. The KOP is focused on an enhanced regional coverage of the sea surface height variability and the baroclinic structure of the mainstream Kuroshio in the East China Sea, the Ryukyu Current east of the Ryukyu's, and the Kuroshio recirculation. An attractive approach of the KOP is a development of a new data acquisition system via acoustic telemetry of the observational data. The monitoring system will provide observations for assimilation into extensive numerical models of the ocean circulation, targeting the real-time monitoring of the Japanese coastal waters.

• 한국해안해양공학회지
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• 제9권3호
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• pp.105-114
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• 1997

바람은 동해의 순환에 기여하는 중요한 외력이다. 1.5층 및 2.5층 감쇠중력 모형을 이용하여 동해의 순환을 시뮬레이션하여 대마난류의 분기, 동해안의 동한난류의 분기, 동한만 및 동해북부에서의 반시계 방향성 순환현상을 기존순환모형도와 비교하였다. 상층과 하층의 양상은 동해의 중앙부를 제외하고는 유사하였는데 극전선이 다음과 같이 서로 다른 두양상을 제시한다. 극전선의 북측의 주양상은 대부분의 계절에 발생하는 3개소의 반시계방향 와동이며 이 와동의 내측연안을 따라서 북한류와 리만한류가 흐른다. 극전선의 남측에서 상하 양층의 해류체계는 겨울과 봄의 상층순환을 제외하고는 시계방향 순환이다. 한국과 러시아 연안을 따라 류속구조는 순압적이나 동해중부는 경압적이다. 바람응력의 계절적 변화와 Ekman 수송(suction/pumping)을 시간변화를 갖는 공간적평균과 공간적변화를 갖는 시간적으로 수정된 바람응력을 부여함으로서 조사하였다. 동해의 서측과 북서측 해역의 반시계방향 와동의 형성에 있어서 바람응력 컬(curl)에 의한 국지적인 Ekman suction/pumping이 중요함을 확인하였다