• Journal of the korean society of oceanography
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• 제31권4호
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• pp.173-182
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• 1996

A median-density fluid was injected into the upper layer of a two-layered fluid in a rotating cylindrical container. Several sets of the top and bottom boundary configurations were employed and the flow pattern of each layer including the injected fluid was observed to determine the factors that affect the path of the injected intermediate fluid. The axisymmetric path of the intermediate fluid when the upper layer had a free surface, changed into the asymmetric path with bulged-shape radial spreading whenever either the upper layer or the lower layer had ${\beta}$-effect. The internal Fronds number that controls the shape of the interface turned out to be the most important parameter that determines the radial spreading in terms of location and strength. When the upper and lower layer had the ${\beta}$-effect, convective overturning produced anticyclonic vortices at the frontal edge of the intermediate fluid, and that could enhance the vertical mixing of different density fluids. The intermediate fluid did not produce any topographic effect on the upper-layer motion during its spreading over the interface, since its thickness was very small. However, its anticyclonic motion within the bulged-shape produced a cyclonic motion in the lower layer just beneath the bulge.

• 한국수산과학회지
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• 제30권6호
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• pp.1033-1043
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• 1997

In order to understand the generation mechanism of the Ulleung Eddy, we carried out a series of numerical experiments using the nonlinear 11/2 - layer model allowing the inflow of the Tsushima Current. According to our numerical results, the Ulleung Eddy was generated due to the inflow variations of the Tsushima Current. Its inflow through the Korea Strait was deflected to the east due to the Coriolis force and the nonlinear self advection. Thus, an anticyclonic motion was formed at the north of the Korea Strait. The inflow became a coastal boundary current, and finally flowed out model ocean through the eastern exit. When the speed of inflow decreased slowly, the eddy- like motion at the north of the Korea Strait changed into an enclosed anticyclonic eddy of about 200 km in diameter. The Ulleung Eddy became circular shape due to the nonlinear self advection, then changed into elliptical shape in meridional direction because of the blocking effect of the western boundary.

• 한국수산과학회지
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• 제28권3호
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• pp.354-363
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• 1995

1992년 1월부터 6월까지의 인공위성 적외선 영상자료를 이용하여 속초 근해에 형성된 와동류의 시간적 변화에 대하여 연구하였고 동년 5월에 그 구조를 관측하였다 와동류의 형성에는 두 가지 종류의 과정이 있는 것으로 나타났는데, 첫 번째로 1월의 영상자료에 의하면 난류의 대량 공급으로 인하여 약 200km 크기의 와동류가 형성되었다. 그 이후에 약간의 변형과 냉각과정을 거쳐서 3월에는 난류의 좁은 필라멘트가 북쪽으로 침투하면서 어느 정도 냉각된 기존의 와동류를 포위함으로써 4-5월에는 반지모양의 와동류로 발달하는 두 번째의 형성과정이었다. 와동류의 내부에는 수온 $10.0-10.4^{\circ}C$의 균질 중층수가 최대 170m의 두께로 존재하였다. 속초 근처 동한난류의 축에서의 유속 약 80cm/sec를 제외하면 나머지 부분의 와동류 내부에는 대체로 30-50cm/sec의 유속분포를 보였고 주수온약층 밑으로는 유속이 급격히 감소하였다.

• 한국지구과학회지
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• 제43권4호
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• pp.511-519
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• 2022

Given the significant social and economic impact caused by heat waves, there is a pressing need to predict them with high accuracy and reliability. In this study, we analyzed the real-time forecast data from six models constituting the Subseasonal-to-Seasonal (S2S) prediction project, to elucidate the key mechanisms contributing to the prediction of the recent record-breaking Korean heat wave event in 2018. Weekly anomalies were first obtained by subtracting the 2017-2020 mean values for both S2S model simulations and observations. By comparing four Korean heat-wave-related indices from S2S models to the observed data, we aimed to identify key climate processes affecting prediction accuracy. The results showed that superior performance at predicting the 2018 Korean heat wave was achieved when the model showed better prediction performance for the anomalous anticyclonic activity in the upper troposphere of Eastern Europe and the cyclonic circulation over the Western North Pacific (WNP) region compared to the observed data. Furthermore, the development of upper-tropospheric anticyclones in Eastern Europe was closely related to global warming and the occurrence of La Niña events. The anomalous cyclonic flow in the WNP region coincided with enhancements in Madden-Julian oscillation phases 4-6. Our results indicate that, for the accurate prediction of heat waves, such as the 2018 Korean heat wave, it is imperative for the S2S models to realistically reproduce the variabilities over the Eastern Europe and WNP regions.

• 한국해양학회지
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• 제30권3호
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• pp.170-183
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• 1995

1992년 11월부터 1993년 9월 사이 동해남서해역에서 조사한 인공위성 추적부 이, CTD, ADCP 자료를 이용하여 와류와 표층해류의 물리적 구조를 분석하였다. 부이의 이동궤적으로부터 울릉분지내에서 동한난류의 사행과 연구해역에서 다양한 크기의 시계방향과 반시계방향의 와류가 존재하는 것을 처음으로 직접 해류조사로 밝힐 수 있었다. 비교적 오래 지속되는 시계방향의 와류가 울릉분지내와 북부(일 본)분지의 남서쪽에서 관측된 반면에 반시계방향의 와류가 속초와 동해시 사이의 연안역에서 여름철에 관측되었다. 울릉분지의 와류는 적어도 관측기간 중에는 분지 내에 머물러 있었으며, 반시계방향의 와류는 냉수의 존재와 밀접한 관련이 있는 것 으로 나타났다. 북부분지의 시계방향 와류는 울릉분지의 것보다 크며 더 길쭉한 타원 형태를 지녔다. 울릉분지의 와류는 주축과 종축이 각각 120 km, 70 km이고, 회전주기는 13.6일, 평균회전속도는 24 cm/s, 평균 와동운동에너지는 392 $cm^{2}$/s$^{2}$ 이다. 북부분지의 와류는 주축과 종축이 각각 168 km, 86 km이고, 회전 주기는 14.9일, 평균회전속도는 29 cm/s, 평균 와동운동에너지는 629 $cm^{2}$/s/ sup 2/ 의 특성을 보였다. 와류의 평균이동속도는 두 경우 모두 약 3 cm/s이다. 울릉분지내에서 ADCP로 관측한 표층해류와 지형류의 상호일치는 울릉분지의 와류 가 지형평형을 이루고 있음을 시사한다. 관측된 와류는 해저지형에 강하게 지배 되어 있다.

• 한국지구과학회지
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• 제40권5호
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• pp.476-486
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• 2019

This study examines the controlling role of synoptic disturbances on $PM_{10}$ spring variability in the Korean Peninsula by using empirical orthogonal function (EOF) and back trajectory analyses. Three leading EOF modes are identified, and a lead-lag analysis suggests that $PM_{10}$ variabilities be closely related to the synoptic weather systems. The first EOF shows the spatially homogeneous distribution of $PM_{10}$, which is influenced by travelling anticyclonic disturbance with negative precipitation and descending motion. The second and third modes exhibit the dipole structures of $PM_{10}$, being associated with propagating cyclones. Furthermore, the back-trajectory analysis suggests that the transport of pollutants by anomalous winds associated with synoptic disturbances also contribute to the altered $PM_{10}$ concentration. Hence, a substantial synoptic control should be considered in order to fully understand the $PM_{10}$ spatiotemporal variability.