• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.1-12
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• 2007

A method to quickly estimate broadband moment magnitudes (Mwp) to warn regional and teleseismic tsunamigenic earthquakes is tested for application of the method to the different seismic observation environment. In this study, the Mwp is calculated by integrating far-field P-wave or pP-wave of vertical component of displacement seismograms in time domain from earthquakes, having magnitude greater than 5.0 and occurred in and around the Korean peninsula from 2000 to 2006. We carefully set up the size of the time window for the computations to exclude S wave phases and other phases following after the P wave phase. The P wave velocities and the densities from the averaged Korean crustal model are used in the computations. Instrumental correction was performed to remove dependency on the seismograph. The Mwp after the instrumental correction is about 0.1 greater than the Mwp before the correction. The comparison of our results to the those of foreign agencies such as JMA and Havard CMT catalogues shows a higher degree of similarity. Thus our results provide an effective tool to estimate the earthquake size, as well as to issue the necessary information to a tsunami warning system when the effective earthquake occurs around the peninsula.

• Korean Journal of Remote Sensing
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• v.38 no.5_3
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• pp.811-818
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• 2022

Recently, the number of natural and environmental disasters is rapidly increasing due to extreme weather caused by climate change, and the scale of economic losses and damage to human life is increasing accordingly. In addition, with urbanization and industrialization, the characteristics and scale of extreme weather appearance are becoming more complex and large in different ways from the past, and need for remote sensing and artificial intelligence technology for responding and managing global environmental disasters. This special issue investigates environmental disaster observation and management research using remote sensing and artificial intelligence technology, and introduces the results of disaster-related studies such as drought, flood, air pollution, and marine pollution, etc. in South Korea performed by the i-SEED (School of Integrated Science for Sustainable Earth and Environmental Disaster at Pukyong National University). In this special issue, we expect that the results can contribute to the development of monitoring and management technologies that may prevent environmental disasters and reduce damage in advance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.2
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• pp.69-83
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• 2018

The South China Sea (SCS) is a typical marginal sea characterized with the deep basin, shelf break, shallow shelf, many straits, and complex bathymetry. This study investigated the tidal characteristics and propagation, and reproduced typhoon-induced storm surge in this region using the regional real-time tide-surge model, which was based on the unstructured grid, resolving in detail the region of interest and forced by tide at the open boundary and by wind and air pressure at the surface. Typhoon Haiyan, which occurred in 2013 and caused great damage in the Philippines, was chosen as a case study to simulate typhoon's impact. Amplitudes and phases of four major constituents were reproduced reasonably in general, and the tidal distributions of four constituents were similar to the previous studies. The modelled tide seemed to be within the acceptable levels, considering it was difficult to reproduce the tide in this region based on the previous studies. The free oscillation experiment results described well the feature of tide that the diurnal tide is prevailing in the SCS. The tidal residual current and total energy dissipation were discussed to understand the tidal and sedimentary environments. The storm-surge caused by typhoon Haiyan was reasonably simulated using this modeling system. This study established the regional real-time barotropic tide/water level prediction system for the South China Sea including the seas around the Philippines through the validation of the model and the understanding of tidal characteristics.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.2
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• pp.83-90
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• 1984

The secular fluctuations of catches and fishing grounds of mackerals and the oceanographic conditions for the fishing grounds are examined by using the data of catches of mackerals by middle and large class purse-seiner during 1951 to 1981 and those of oceanographic observation carried out by Japan Meteorological Agency. The results are as follows; The fishing grounds of mackerals are respectively distributed at northeastern and southwestern areas from the central part of the East China Sea through every season of the studied years: 1968, 1974 and 1980. The narrow belt type of fishing grounds were formed inside of the Kuroshio in spring and winter of the three years. In summer mackeral species move northward and the fishing grounds are formed in the southern sea of Korea. In winter, however, mackeral species move southward and the fishing grounds are appeared in the Tsushima Current region. The dispersion of fishing grounds is generally larger in summer and smaller in spring, and especially it is the largest in summer in 1980. It seems that the concentration and dispersion of fishing grounds are related to the depth of thermocline and the position of horizontal temperature gradient in this area.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.313-319
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• 2007

Long term wave climate of both extreme and operational wave height is essential for planning and designing coastal structures. Since the availability of the field wave data for the waters around Korean peninsula is limited to provide a reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. In this paper, a set of deep water wave data obtained from KORDI(2003) were analyzed for extreme wave heights. These wave data at 67 stations off the Korean coast from 1979 to 1998 were arranged in the 16 directions. The probability distributions considered in this research were the FT-I and Weibull distribution. For each of these distributions, the method proposed by Goda(2004) was applied to estimate the parameters. For judgment of best fitting, MIR criterion proposed by Goda and Gobune(1990) was used. FT-I distribution which best fits to the 886 data, while Weibull(k=0.75) 81 data, Weibull(k=1.00) 105 data.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.151-151
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• 2023

본 연구는 호우(heavy rain) 발생 시 대기 중 미세먼지(particulate matter, PM) 저감효과를 규명하고 강우 지속에 따른 빗물 수질(pH, 전기전도도(electrical conductivity, EC), 수용성 이온) 분석을 통해 대기 중 PM이 빗물 수질에 미치는 영향을 평가하였다. 2020년 3월부터 2021년 2월까지강우 강도(7.5 mm/h)를 기준으로 총 6회의 강우를 대상으로 하였으며 빗물 샘플은 집수장치를 통해 50 mL를 연속적으로 수집하여 수질을 분석하였다. 대기 중 PM_2.5 (≤ 2.5 ㎛ in diameter) 및 PM₁₀ (≤ 10 ㎛ in diameter) 농도는 기상청 내 부산 남구 대연동 관측소의 automatic weather system (AWS)에서 측정된 일평균 자료를 이용하였다. 강우에 따른 대기 중 PM의 저감효율은 상대적으로 PM₁₀에서 뚜렷하게 나타났으며, 특히 강우 강도 7.5 mm/h 이상(유형 1)의 호우 발생 시60% 이상의 저감효율을 보였다. 반면, 강우 강도 7.5 mm/h 이하(유형 2)일 때는 10% 이하의 저감효율을 보였으며, 강우 지속에 따라 대기 중 PM₁₀ 농도가 증가하는 경향을 보이기도 하였다. 총108개의 빗물 샘플 수질을 분석한 결과, 유형 1의 경우 초기 빗물의 평균 EC는 58.5 µS/cm으로 상대적으로 높았으며 대기 중 PM₁₀과 양의 상관관계(r = 0.99)를 보였고 평균 pH는 4.3으로 산성도가 높게 나타났으며 대기 중 PM₁₀과 음의 상관관계(r = -0.99)를 보였다. 반면, 유형 2의 경우 대기 중 PM₁₀과 EC (r = -0.56) 및 pH (r = -0.41) 간 뚜렷한 상관관계가 나타나지 않았다. 또한 강우가 지속됨에 따라 EC와 수용성 양이온(Na⁺, Mg²⁺, K⁺, Ca²⁺, NH₄⁺) 및 음이온(Cl^-, NO₃^-, SO₄^2-)의 농도는 지속적으로 감소하는 경향을 보였으나 pH의 경우 강우 강도에 따라 증감의 경향이 다르게 나타났다. 유형 1의 경우 강우 지속에 따라 pH가 증가하여 산성도가 낮아졌으나 유형 2는 pH의 증감 형태를 뚜렷하게 확인하기 어려웠다. 연구 결과를 통해 강우 초기 높은 강도로 강우가 지속될 경우 대기 중 PM₁₀이 빗물 수질에 영향을 미칠 수 있는 것으로 판단되며, 이에 따라 호우 발생 시 강우가 대기 중 오염물질을 지표면으로 유입시킬 수 있는 매개체로 작용할 수 있음을 지시한다.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.19-31
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• 2023

According to the climate change scenarios, the intensity of typhoons, a major factor in Korea's natural disaster, is expected to increase. The increase in typhoon intensity leads to a rise in wave heights, which is likely to cause large-scale disasters in coastal regions with high populations and building density for dwelling, industry, and tourism. This study, therefore, analyzed observation data of the Donghae ocean data buoy and conducted a numerical model simulation for wave estimations for the typhoon MAYSAK (202009) period, which showed the maximum significant wave height. The boundary conditions for wave simulations were a JMA-MSM wind field and a wind field applying the typhoon central pressure reduction rate in the SSP5-8.5 climate change scenario. As a result of the wave simulations, the wave height in front of the breakwater at Sokcho port was increased by 15.27% from 4.06 m to 4.68 m in the SSP5-8.5 scenario. Furthermore, the return period at the location of 147-2 grid point of deep-sea design wave was calculated to increase at least twice, it is necessary to improve the deep-sea design wave of return period of 50-year, which is prescriptively applied when designing coastal structures.

• Journal of Navigation and Port Research
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• v.31 no.3 s.119
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• pp.263-269
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• 2007

The outbreaks of red tide were sporadic in the South Sea until 1994, but have become frequent and widespread in whole coastal waters of the South Sea and East Sea since 1995 For monitoring of red tide, many kinds of techniques such as remote sensing, GIS and fuzzy model system have been developed and applied. The purpose of this paper is to develop red tide monitoring system for collection of red tide data and biological-oceanography parameters using wireless sensor network. The wireless sensor network has been noticed as a core technology in order to realize ubiquitous computing. In this paper, we design red tide database using wireless sensor network and suggest red tide monitoring software and web-service for user and biological-oceanographer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.20-25
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• 2012

The COMS, which is a multi-purposed satellite that provide the oceanic measurement data and meterological image data, is operating since 2010. Ka-band satellite communication transponder in COMS gets the MSM function that can provide the required multi-beam and transmits the multi-mode signal with high data rate. The phase noise of COMS communication transponder can be increased because of several local oscillators for MSM function and the utilization of Ka-band frequency. The phase noise affects the performance for the multi-mode and high rate data based- transmission method, it is not possible to recover the transmission data in system with the high system phase noise. In this paper, the phase noise of COMS was measured and the effects of the measured phase noise are analysed and evaluated in the viewpoint of the noise bandwidth of transmission system, Also the transmission performances for multi-mode and high rate data are evaluated in the presence of COMS phase noise.

• Ocean and Polar Research
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• v.36 no.2
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• pp.103-110
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• 2014

A wind-driven current in the East Sea from Lagrangian measurements of wind and current at 15 m using MiniMet drifters was analyzed. Spectral analysis of the current from 217 pieces of a 10 day-long time series shows the dominant energy at the inertial frequency for the current at 15 m. Wind has energy peaks at a 0.2-0.5 cycles per day (cpd) frequency band. The power spectrum of the clockwise rotating component is predominant for the current and was 1.5-2 times larger than the anticlockwise rotating component for wind. Co-spectra between the wind and current show two peak frequency bands at subinertial frequency and 0.5-0.3 cpd. Coherences between the wind and current at those peak frequencies are significant with 95% confidence and phase differences were $90-100^{\circ}$. From the phase differences, the efolding depth is estimated as 17 m and this e-folding depth is smaller than the estimation by Chereskin's (1999) 25 m using a moored Acoustic Doppler Current Profiler and an anemometer installed at the surface buoy. The angle between the wind-driven current (or ageostrophic current) and wind from this study was also much larger than the global estimate by Rio and Hernandez (2003) using reanalysis wind and drifters. The possible explanation for the discrepancy comes from the fact that the current is driven by a wind of smaller length scale than 250 km but the satellite or the reanalysis products do not resolve winds of length scale smaller than 250 km. Large rms differences between Mini-Met and QuickSCAT wind on spatial lags smaller than 175 km substantiate this explanation.