• Journal of Korea Water Resources Association
• /
• v.48 no.12
• /
• pp.1023-1035
• /
• 2015

This study applies 3-D N-S solver based on PBM (Porous Body Model), LED-WASS-3D ver 2.0 to directly analyze non-linear interaction of seawater-freshwater-coastal aquifer in order to simulate the seawater infiltration into coastal aquifer. This numerical simulation is the first trial in Korea, as well as unusual and new numerical analysis abroad. Firstly, to validate the applied numerical model, the validity and effectiveness was verified for the numerical model by comparing and considering it with the result of laboratory experiment for seawater-freshwater interface in coastal aquifer. And then it simulated the seawater infiltration into coastal aquifer considering the changed levels of seawater and groundwater in order to analyze the distribution characteristics of flow field and seawater-freshwater interface of coastal aquifer as the level difference between seawater and groundwater and rate of seawater level (${\Delta}h/h$) increased. In addition, the characteristics of seawater infiltration were analyzed from the vertical salinity in the coastal aquifer by ${\Delta}h/h$, which cannot be obtained from existing non-diffusion numerical models. Finally, it analyzed the effect of ${\Delta}h/h$ on the seawater infiltration distance in coastal aquifer, which was indexed.

• Journal of Korea Water Resources Association
• /
• v.38 no.12 s.161
• /
• pp.995-1008
• /
• 2005

In this study, the principal components of rainfall in Korea are extracted by a method which consists of the independent component analysis combined with the wavelet transform, to examine the spatial correlation between seasonal rainfalls and global sea surface temperatures (SSTs). The 2-8 year band retains a strong wavelet power spectrum and the low frequency characteristics are shown by the wavelet analysis. The independent component analysis is performed by using the Scale Average Wavelet Power(SAWP) that is estimated by wavelet analysis. Interannual-interdecadal variation is the dominant variation, and an increasing trend is observed in the spring and summer seasons. The relationships between principal components of rainfall in the spring/summer seasons and SSTs existed in Indian and Pacific Oceans. Particularly, the SST zones, which represent a statistically significant correlation are located in the Philippine offshore and Australia offshore. Also, the three month leading SSTs in the same region we strongly correlated with the rainfall. Hence, these results propose a promising possibility of seasonal rainfall prediction by SST predictors.

• Korean Journal of Remote Sensing
• /
• v.37 no.3
• /
• pp.603-614
• /
• 2021

Recently, the surface temperature in the seas around Korea has been continuously rising. This temperature rise causes changes in fishery resources and affects leisure activities such as fishing. In particular, high temperatures lead to the occurrence of red tides, causing severe damage to ocean industries such as aquaculture. Meanwhile, changes in sea temperature are closely related to military operation to detect submarines. This is because the degree of diffraction, refraction, or reflection of sound waves used to detect submarines varies depending on the ocean mixed layer. Currently, research on the prediction of changes in sea water temperature is being actively conducted. However, existing research is focused on predicting only the surface temperature of the ocean, so it is difficult to identify fishery resources according to depth and apply them to military operations such as submarine detection. Therefore, in this study, we predicted the temperature of the ocean mixed layer at a depth of 38m by using temperature data for each water depth in the upper mixed layer and meteorological data such as temperature, atmospheric pressure, and sunlight that are related to the surface temperature. The data used are meteorological data and sea temperature data by water depth observed from 2016 to 2020 at the IEODO Ocean Research Station. In order to increase the accuracy and efficiency of prediction, LSTM (Long Short-Term Memory), which is known to be suitable for time series data among deep learning techniques, was used. As a result of the experiment, in the daily prediction, the RMSE (Root Mean Square Error) of the model using temperature, atmospheric pressure, and sunlight data together was 0.473. On the other hand, the RMSE of the model using only the surface temperature was 0.631. These results confirm that the model using meteorological data together shows better performance in predicting the temperature of the upper ocean mixed layer.

• Proceedings of the IEEK Conference
• /
• 2001.09a
• /
• pp.521-524
• /
• 2001

신호 대 잡음비가 매우 낮은 수중 음원을 탐지하기 위해서는 많은 센서를 갖는 견인 배열 시스템을 운용하여야 한다. 그러나 이러한 경우 수백 미터에 이르는 배열을 견인함이 끌고 다닐 때 파도와 같은 해수면의 움직임과 견인선의 기동 형태에 따라 원하는 배열 형태를 항상 유지할 수 없다. 그러므로 본 논문에서는 실제 수 중 환경에서 견인되는 배열의 왜곡된 형태를 시간적으로 뿐만 아니라 공간적으로 통합된 센서의 움직임 근거로 한 상관 형태를 잘 표현한 ""Paidoussis"" 방정식을적용하여 이 방정식의 간단화된 형태인 수차 모형(Water pulley)배열을 협대역 목표물 탐지에 이용하였다. [1][2][8] 수차 모형 구조의 배열을 이용하여 사상 기법을 적용하면 수차 모형의 왜곡 특성으로 인해 센서간 간격이 비균일성을 가지는 가상의 선형 배열이 형성되어 진다. 본 논문에서는 사상 기법에 의해 생성된 가상의 선형 배열을 토대로 합성 어패처 방식의 일종인 FFTSA(Fast Fourier Transform Synthetic Aperture) 기법을 이용하여 센서 배열의 입사각 추정 성능에 중대한 영향을 부여하는 코히어런스 주기에 따른 추정 성능의 변화 및 견인함의 이동 경로 변화에 따른 변동 경로 주기에 따른 성능 변화를 분석하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2015.10a
• /
• pp.161-162
• /
• 2015

근대사회는 기술의 발달과 산업화에 의해 도시에 인구가 밀집됨으로써 효율화, 평균화, 획일화된 개발로 대도시가 형성되었다. 이후에는 도시 자체의 팽창으로 인하여 주변 지역으로의 도시권 확대를 위한 개발이 진행되었으며 연안지역에서는 해수면 매립이라는 방법으로 도시 영역을 바다로 확장하였다. 본 연구에서는 연안역의 특성을 고려한 개발을 통해 기후 및 온열환경, 풍환경 등의 영향을 최소화하고 내륙화되는 것을 방지하는 것에 착목하여 연안역이 갖는 기후환경적 이점을 유지하면서 개발이 이루어지기 위해서는 먼저 연안역의 특성을 파악하고, 개발에 의해 변화되는 환경요소를 유형화하여 연안역 기후환경에 미치는 영향력을 분석할 필요가 있다. 이에 본 연구에서는 연안지역의 지형이나 기후와 같은 특성을 조사하고 개발에 따른 연안역의 변화과정을 메커니즘화하여 영향요소를 도출하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.155-155
• /
• 2016

화석연료 사용으로 인한 지구온난화는 평균 기온 및 해수면 상승과 함께 기후변화를 야기하여 수자원 관리에 어려움을 증대시키고 있다. 우리나라도 기후변화로 인한 홍수 및 가뭄의 피해가 커지고 있으며 심도 또한 증대되고 있는 추세이다. 이러한 문제를 해결하기 위해 수자원 시설물을 건설하여 대비하고 있지만 설계 당시 이용할 수 있었던 수문자료의 한계로 인해 최근 발생하고 있는 문제를 해결하기엔 어려움이 있다. 또한 대부분의 다목적댐은 가뭄과 같은 비상 상황에 활용할 수 있도록 비상용량을 확보하고 있음에도 불구하고 사용에 관한 명확한 기준이 없어 거의 활용되지 않고 있는 실정이다. 본 연구에서는 가뭄에 취약한 낙동강 유역 중 이수용량 대비 비상용량이 가장 큰 합천댐을 대상으로 HEC-ResSim 모형을 이용하여 실제 다목적댐에 적용된 용수공급조정 기준을 고려한 비상용량 활용에 따른 용수공급능력 변화를 모의하였다.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.17 no.1
• /
• pp.50-60
• /
• 2014

The purpose of this study is to identify characteristics and improvements of the climate change vulnerability analysis methods to build a safe city from disasters. For this, an empirical analysis on sea level rise disasters was performed focusing on Heaundae-gu in Busan. For the analysis, Census output areas and Dongs were set as analysis unit and their disaster vulnerability was analyzed. Improvements were reviewed through the comparison and review of analysis process and results. According to analysis results, Modifiable Areal Unit Problem(MAUP) which gives different results according to aggregate unit occurs. Improvements were induced by analysis process, and it was found that in spatial unit setting stage that becomes the base of analysis, analysis unit adjustment, score computation method adjustment, and clearer analysis method for each disaster type would be needed. In analysis execution stage, it was thought that weighting according to variables, diversification of variables, and exclusion of subjective analysis selection method would be needed. It is expected that accurate the total disaster vulnerability analysis will be the base for the improvement of efficiency in urban resilience responding to future weather changes.

• Journal of the Korean earth science society
• /
• v.29 no.6
• /
• pp.454-465
• /
• 2008

Benthic foraminiferal assemblage and AMS radiocarbon dating of core sediments from the northern shelf of the East China Sea were analyzed in order to understand the paleoenvironment and sedimentary environmental changes around the Korean marginal seas since the last glacial maximum (LGM). The core sediments, containing continuous records of the last 16,000 years, reveal a series of well-defined vertical changes in number of species (S), P/T ratio and species diversity (H) as well as foraminiferal assemblage. Such down-core variations display a sharp change at a core depth of approximately 240 cm, which corresponds to ca. 10,000 year B.P. The sediments of the lower part of the core (240${\sim}$560 cm, Zone I), including the well-developed tide-influenced sedimentary structures, are characterized by high abundances of Ammonia beccarii and Elphidium clavatum (s.l.) and low values in number of species, P/T ratio and diversity. These tide-influenced signatures and foraminiferal assemblage characters suggest that the sediments of Zone I were deposited in a coastal environment (water depths of 20${\sim}$30 m) such as tidal estuary with an influence of the paleo-rivers (e.g., old-Huanghe and Yangtze rivers) during the early phase of the sea-level rise (ca. 16,000 to 10,000 years) since the LGM. In contrast, the upper core sediments (0${\sim}$240 cm, Zone II) are characterized by abundant Eilohedra nipponica and Bolivina robusta with a minor contribution of A. ketienziensis angulata and B. marginata. and high values in number of species, P/T ratio and diversity. Based on relative abundance of these assemblage, Zone II can be divided into two subzones (IIa and IIb). Zone IIa is interpreted to be deposited under the inner-to-middle shelf environment during the marine transgression in the early Holocene (after ca. 9,000 yr B.P.) when sea level rapidly increased. The sediments of zone IIb most likely deposited after 6,000 yr B.P. under the outer shelf environment (80${\sim}$100 m water depth), which is similar to modem depositional environments. The muddy sediments of zone IIb were probably transported from the old-Huanghe and Yangtze Rivers during the late Holocene. We suggest that the present-day oceanographic conditions over the Yellow and the East China Seas have been established after ca. 7,000${\sim}$6,000 yr B.P. when the Kuroshio Current began to influence this area.

• The Korean Journal of Petroleum Geology
• /
• v.9 no.1_2 s.10
• /
• pp.1-15
• /
• 2001

Hierarchically controlled sequence stratigraphic analysis shows that the Lower Ordovician mixed carbonatesiliciclastic Mungok Formation, Korea consists of three depositional sequences: T1, T2, and T3 in ascending order. Sequence boundaries are generally marked by abrupt transition from coarse-grained shallow-water carbonates to finegrained deeper-water carbonates mixed with fine-grained siliciclastics, and show indication of subaerial exposure such as karstification. Within this sequence stratigraphic framework, facies characteristics indicate that the Mungok sequences were mostly deposited on a subtidal ramp without slope break. The Mungok ramp had been under the influence of frequent tropical storm activity during deposition. The difference in lithology of tempestites seems to have been controlled by the nature of substrates and by proximality. High-frequency cycles consist of upward-shallowing facies successions. Cycles of shallow-water and basinal deposits are not well represented, probably due to cycle amalgamation. Cycle stacking patterns do not show a consistent thickness change that is usually associated with a large-scale sea-level change probably because of unfilled accommodation space.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.1041-1047
• /
• 2008

기후변화로 인한 자연재해가 전 세계적으로 빈번히 발생하고 있는 요즘, 기후변화에 대한 관심이 부쩍 높아지고 있다. IPCC 4차보고서(2007)에서는 기후변화의 영향으로 인한 재해발생 증가가 불가피함을 지적하고 기후변화의 악영향을 최소화하기 위한 적응조치의 중요성을 권고하고 있다. 국내에서도 이미 기후변화로 인한 영향이 자연환경 및 생활환경 전반에 끼칠 정도로 빠르게 진행되고 있음을 다방면의 연구를 통해 드러나고 있다. 그러나 현재까지는 기후변화에 대한 전반적인 인식 부족, 대응제도 및 장치의 미비와 더불어 이에 대한 연구가 부족한 실정이다. 본 연구에서는 기후변화의 징후현상 및 이에 기인한 자연재해의 이력을 조사하고 향후 재해 발생 및 증가추이에 대한 예측 자료를 분석하여 기후변화로 인한 자연재해의 대응책 마련에 필요한 기초적인 자료를 제공하고자 한다. IPCC 4차 보고서 및 국내외 연구문헌 등을 조사하여 기후변화에 따른 재해에 대해 분석한 결과 전 세계적으로 실제 강우 및 기온, 해수면 상승 등에 대한 재해는 해마다 증가하는 추세이며 향후 이에 대한 대책마련이 시급한 것으로 확인되었다. 국내에서도 기후변화에 기인한 홍수 및 태풍 등의 재해로 인해 많은 피해가 발생하고 있으며 향후 이러한 영향이 더욱 증가될 것으로 예측되고 있다. 이러한 기후변화의 영향이 이미 자연재해로 이어지고 있는 만큼 이에 대처하기 위한 전문 인력 양성 및 국가차원에서의 장기적인 제도마련 등이 필요할 것으로 사료되었다.