• Journal of Korean Society for Atmospheric Environment
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• v.32 no.4
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• pp.372-383
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• 2016

This study aimed at analyzing the sensitivity of ozone simulation in accordance with the meteorological nudging for a high nocturnal ozone episode. To demonstrate the effectiveness of nudging methods (e.g., nudging techniques and application domains), the following six experiments were designed: (1) control without nudging, (2) experiment with application of observation nudging to all domains (domain 1~4), and (3)~(6) experiments with application of grid nudging to domain 1, domain 1~2, domain 1~3 and all domains, respectively. As a result, the meteorological nudging had a direct (improvement of input data) and indirect (estimate natural emission) effect on ozone simulation. Nudging effects during the daytime were greater than those during the nighttime due to low accuracy of wind direction during the nighttime. On comparison of the nudging techniques, the experiments in which grid nudging was applied showed more improved results than the experiments in which observation nudging was applied. At this time point, the simulated concentrations were generally similar to the observed concentrations due to the increase in the nudging effect when grid nudging was applied up to the sub-domain. However, for high nocturnal ozone uptakes, the experiment in which grid nudging was applied do domain 1~3 showed better results than the other experiments. This is because, when grid nudging was applied to the high resolution domain (e.g., domain 4 with 1 km), the local characteristics were removed due to the smoothing effects of meteorological conditions.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05b
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• pp.1179-1186
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• 2002

Macro scale distributed hydrological models simulate river discharge with better accuracy but it depends upon the grid resolution of input data. Effects of different input resolutions are studied here. Three different grid resolution input data obtained from HUBEX-IOP EEWB data and GAME Re-analysis data are used to simulate river discharge and compared against the observed one. CAME Re-analysis 1.25-degree resolution data are found quite satisfactory in larger basins, while HUBEX-IOP EEWB 10-minute resolution data are better for small catchments. GAME Re-analysis 2.5-degree resolution data did not give good result. Simulated results by using spatially interpolated data are rather worse than using original data. The Huaihe River basin $(132350\textrm{km}^2)$ is taken as the case of study.

• Water Engineering Research
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• v.5 no.2
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• pp.81-99
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• 2004

Long term streamflow regime under virtual climate change scenario was examined. Rainfall forecast simulation of the Canadian Global Coupled Model (CGCM2) of the Canadian Climate Center for modeling and analysis for the IPCC SRES B2 scenario was used for analysis. The B2 scenario envisions slower population growth (10.4 billion by 2010) with a more rapidly evolving economy and more emphasis on environmental protection. The relatively large scale of GCM hinders the accurate computation of the important streamflow characteristics such as the peak flow rate and lag time, etc. The GCM rainfall with more than 100km scale was downscaled to 2km-scale using the space-time stochastic random cascade model. The HEC-HMS was used for distributed hydrologic model which can take the grid rainfall as input data. The result illustrates that the annual variation of the total runoff and the peak flow can be much greater than rainfall variation, which means actual impact of rainfall variation for the available water resources can be much greater than the extent of the rainfall variation.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.697-703
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• 2002

In the present study, space allocation methods of pollutant emission from area and mobile sources are assessed by the actual application to air quality modeling of Pohang area. It is found that the TM-based modeling which allocates emission onto the 1km x 1km sized TM-grid system predicts almost the same mean ground-level concentration as that by the GIS-based modeling which uses geographical information of area and mobile sources directly, while maximum ground-level concentration by the TM-based modeling is predicted considerably lower than that by the GIS-based modeling. Moreover, the problem is found that the TM-based modeling causes deviation of mobile roads. In conclusion, it is anticipated to applying GIS-based modeling for a more accurate assessment of air quality in local scale.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.124-136
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• 2006

The change pattern of the sediment grain size distribution information (median grain size(D50)) due to some gridding method and sampling density is analyzed with reference to the grid information estimated by the 90 sediment samples which was collected in the coastal water off the Baengnyeongdo Island, in June 2004. The standard deviation of absolute deviation (AD) estimated the selected gridding method shows 8.0 ${\mu}m$ at June, 2004 and 10 ${\mu}m$ November, 2004. The estimated statistical information of absolute deviation in comparison with the grid information of reference and changed sampling density shows that the AD mean error trends increase as the number of samples decrease. The AD mean error is below 10% in the case of the information estimation using 50-sample with reference to the 90-sample information. In this case, the sampling density is suggested as about 9 sediment samples per $km^2$, at coastal zone in Yoggipo port in the condition of the study area is 5.9 $km^2$.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.4 no.1
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• pp.9-15
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• 2023

We analyzed data of endangered mammals in the 1st grade zone of the Ecological and Natural Map of Korea that were obtained through 202 field surveys over six years. Five endangered mammal species were identified including otters, long-tailed gorals, martens, leopard cats, and flying squirrels. The total number of habitat traces collected was 918, of which 897 traces (97.7%) were excrement types. The total surveyed distance was 697.7 km and there were 2,184 grids of 250×250 m each. Of these grids, 441 or 20.2% were confirmed as habitats of endangered mammals. Moreover, we analyzed results of repeated surveys in the same area by converting them into individual one-time surveys, accounting for 23.1% of the total area. The flying squirrel showed a low correlation with the frequency of field surveys but showed many habitats in a specific season. Leopard cats and martens were correlated with the frequency of field surveys. Results of analysis confirm that the grid method used for establishing the Ecological and Natural Map is unsuitable for the habitat division of flying squirrels, otters, leopard cats, and martens, and it does not reflect the actual habitats of these four species. Therefore, we propose that the concept of the habitat grid of species must be reevaluated and improved, specifically for endangered mammals.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.6
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• pp.265-273
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• 2023

This study proposes a methodology for the regional seismic risk assessment of structural damage to buildings in Korea based on evaluating individual buildings, considering inconsistency between the administrative district border and grid lines to define seismic hazard. The accuracy of seismic hazards was enhanced by subdividing the current 2km-sized grids into ones with a smaller size. Considering the enhancement of the Korean seismic design code in 2005, existing seismic fragility functions for seismically designed buildings are revised by modifying the capacity spectrum according to the changes in seismic design load. A seismic risk index in building damage is defined using the total damaged floor area considering building size differences. The proposed seismic risk index was calculated for buildings in 29 administrative districts in 'A' city in Korea to validate the proposed assessment algorithm and risk index. In the validation procedure, sensitivity analysis was performed on the grid size, quantitative building damage measure, and seismic fragility function update.

• Asian Journal of Atmospheric Environment
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• v.4 no.2
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• pp.89-96
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• 2010

To identify the domains that have the greatest impacts on air quality at the surface, both the upwind and downwind areas of Seoul were determined by season using refined wind fields. Four consecutive days were selected as the study period typical of each season. The mesoscale meteorology of the study period was reproduced by using the MM5 prognostic meteorological model (PSU/NCAR Mesoscale Model) with horizontally nested grids. The gridded meteorological field, which was used on the study area of $242\;km{\times}226\;km$ with grid spacing of 2 km, was generated by using the CALMET diagnostic meteorological model. Upwind and downwind areas of Seoul were determined by calculating 24-hour backward and forward air parcel trajectories, respectively, with u, v, and w velocity vectors. The results showed that the upwind and downwind areas were extended far to the northwest and the southeast as a result of high wind speeds in the spring and winter, while they were restricted on the fringe of Seoul in the summer and fall.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.207-207
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• 2023

데이터 기반 강수 예측 모델은 극한 강수 이벤트의 크기를 과소 추정하는 경향이 있다. 이는 훈련 데이터에 극한 강수 이벤트보다 일반적인 강수 이벤트가 많이 포함되어 있기 때문이다. 본 연구는 이러한 딥러닝의 데이터 불균형 문제를 해소하고자 모델을 학습시킬 때 격자별 극한 강수에 더 큰 가중치를 주어 극한 강수 예측의 정확성을 높이는 방법을 제안한다. 딥러닝 모델 중 공간-시간 필드를 정확하게 예측할 수 있는 ConvLSTM 기반 강수 예측 모델을 활용하여 레이더 강수량을 예측하였다. 먼저, 훈련 기간 동안의 강수 이벤트의 누적 분포 함수 CDF(Cummulative distribution funcion)을 그린 후 극한 강수 이벤트와 일반적인 강수 이벤트의 분포를 확인하였다. 그다음, 적은 분포를 가진 극한 강수 이벤트의 더 큰 가중치를 두어 모델을 학습시켰다. 이 모델은 대한민국 중부 지역 (200km x 200km)의 5km-10분 해상도 레이더-계량기 복합 강수 필드에 대해 2009-2014년 기간 동안 훈련 되었고 2015-2016년 동안 모델의 훈련을 검증 하였고, 2017-2018년 동안 테스트 되었다. 다양한 가중치 함수를 기반으로 훈련 시킨 결과 최적화 가중치 함수 모델의 평균 NSE는 0.6 평균 RMSE는 0.00015 그리고 극한 강수 이벤트만 따로 추출한 평균 MAE는 6이다. 결과적으로 제안된 모델은 기존 방법에 비해 예측 성능을 향상 시켰으며, 격자별 가중치를 두었을 경우 일반적인 강수 이벤트 뿐만 아니라 극한 강수 이벤트의 예측의 정확도를 향상시켰다.

• Economic and Environmental Geology
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• v.31 no.2
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• pp.127-139
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• 1998

A new technique of simultaneous inversion for 3-D seismic velocity structure by using direct, reflected, and refracted waves is applied to the southeast part of the Korean Peninsula including Pohang Basin, Kyongsang Basin and Ryongnam Massif. Pg, Sg, PmP, SmS, Pn, and Sn arrival times of 44 events with 554 seismic rays are inverted for locations and crustal structure. $6{\times}6$ with $0.5^{\circ}$ and 8 layers (4 km each layer) model was inverted. 3-D seismic crustal velocity tomography including eight sections from surface to Moho, ten profiles along latitude and longitude are analyzed. The results are as follows: 1) the average velocity and thickness of sediment are 5.04 km/s and 3-4 km, and the velocity of basement is 6.11 km/s. The shape of velocity in shallower layer is agreement with Bouguer gravity anomaly (Cho et al., 1997). 2) the velocities fluctuate strongly in the upper crust. The velocity distribution of the lower crust under Conrad appears basically horizontal. 3) the average depth of Moho is 30.4 km, and velocity is 8.01 km/s. 4) from the velocity and depth of the sediment, the thickness, velocity and form of the upper crust, and the depth and form of Moho, we can find the obvious differences among Ryongnam Massif, Kyongsang Basin and Pohang Basin. 5) the deep faults (a Ulsan series faults) near Kyongju and Pohang areas can be found to be normal and/or thrust faults with detachment extended to the bottom of the upper crust.