• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.197-207
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• 2016

This study aims at providing basic data to objectively evaluate the areas suitable for reintroduction of the species of Asiatic black bear (Ursus thibetanus) in order to effectively preserve the Asiatic black bears in the Korean protection areas including national parks, and for the species restoration success. To this end, this study predicted the potential habitats in East Asia, Southeast Asia and India, where there are the records of Asiatic black bears' appearances using the Maxent model and environmental variables related with climate, topography, road and land use. In addition, this study evaluated the effects of the relevant climate and environmental variables. This study also analyzed inhabitation range area suitable for Asiatic black and geographic change according to future climate change. As for the judgment accuracy of the Maxent model widely utilized for habitat distribution research of wildlife for preservation, AUC value was calculated as 0.893 (sd=0.121). This was useful in predicting Asiatic black bears' potential habitat and evaluate the habitat change characteristics according to future climate change. Compare to the distribution map of Asiatic black bears evaluated by IUCN, Habitat suitability by the Maxent model were regionally diverse in extant areas and low in the extinct areas from IUCN map. This can be the result reflecting the regional difference in the environmental conditions where Asiatic black bears inhabit. As for the environment affecting the potential habitat distribution of Asiatic black bears, inhabitation rate was the highest, according to land coverage type, compared to climate, topography and artificial factors like distance from road. Especially, the area of deciduous broadleaf forest was predicted to be preferred, in comparison with other land coverage types. Annual mean precipitation and the precipitation during the driest period were projected to affect more than temperature's annual range, and the inhabitation possibility was higher, as distance was farther from road. The reason is that Asiatic black bears are conjectured to prefer more stable area without human's intervention, as well as prey resource. The inhabitation range was predicted to be expanded gradually to the southern part of India, China's southeast coast and adjacent inland area, and Vietnam, Laos and Malaysia in the eastern coastal areas of Southeast Asia. The following areas are forecast to be the core areas, where Asiatic black bears can inhabit in the Asian region: Jeonnam, Jeonbuk and Gangwon areas in South Korea, Kyushu, Chugoku, Shikoku, Chubu, Kanto and Tohoku's border area in Japan, and Jiangxi, Zhejiang and Fujian border area in China. This study is expected to be used as basic data for the preservation and efficient management of Asiatic black bear's habitat, artificially introduced individual bear's release area selection, and the management of collision zones with humans.

• Korean Journal of Remote Sensing
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• v.31 no.3
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• pp.227-244
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• 2015

Synthetic Aperture Radar is able to provide images of wide coverage in day, night, and all-weather conditions. Recently, as the SAR image resolution improves up to the sub-meter level, their applications are rapidly expanding accordingly. Especially there is a growing interest in the use of geographic information of high resolution SAR images and the change detection will be one of the most important technique for their applications. In this paper, an automatic threshold tracking and change detection algorithm is proposed applicable to high-resolution SAR images. To detect changes within SAR image, a reference image is generated using log-ratio operator and its amplitude distribution is estimated through K-S test. Assuming SAR image has a non-gaussian amplitude distribution, a generalized thresholding technique is applied using Kittler and Illingworth minimum-error estimation. Also, MoLC parametric estimation method is adopted to improve the algorithm performance on rough ground target. The implemented algorithm is tested and verified on the simulated SAR raw data. Then, it is applied to the spaceborne high-resolution SAR images taken by Cosmo-Skymed and KOMPSAT-5 and the performances are analyzed and compared.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.423-433
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• 2019

In order to predict the seabed topography change due to the construction of offshore wind power structures in the west-southern sea of Korea, field observations for tides, tidal currents, suspended sediment concentrations and seabed sediments were carried out at the same time. These data could be used for numerical simulation. In numerical experiments, the empirical constants for the suspended sediment flux were determined by the trial and error method. When a concentration distribution factor was 0.1 and a proportional constant was 0.05 in the suspended sediment equilibrium concentration formulae, the calculated suspended sediment concentrations were reasonably similar with the observed ones. Also, it was appropriate for the open boundary conditions of the suspended sediment when the south-east boundary corner was 11.0 times, the south-west was 0.5 times, the westnorth 1.0 times, the north-west was 1.0 times and the north-east was 1.0 times, respectively, using the time series of the observed suspended sediment concentrations. In this case, the depth change was smooth and not intermittent around the open boundaries. From these calibrations, the annual water depth change before and after construction of the offshore wind power structures was shown under 1 cm. The reason was that the used numerical model for the large scale grid could not reproduce a local scour phenomenon and they showed almost no significant velocity change over ± 2 cm/s because the jacket structures with small size diameter, about 1 m, were a water-permeable. Therefore, it was natural that there was a slight change on seabed topography in the study area.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.224-228
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• 2008

2007년 세계경제포럼(WEF)은 우리가 직면한 최우선 해결과제로 기후변화를 언급하였다. 최저 기온 상승과 가뭄 영향 지역 확대, 폭염일수와 지역적 홍수 위험 증가 등 각종 이상기상이 야기하는 피해 확대에 대한 예상과 우려 때문이다(IPCC, 2007). 세계적으로 고온극한과 호우빈도 증가, 태풍 세기가 강화될 것으로 전망되고 있으며(IPCC, 2007), 국내의 경우 겨울철 한파 감소와 대설 피해 증가, 여름철 집중호우의 강도 심화, 가을철 초대형 태풍 발생으로 인한 피해 가능성이 예측 되고 있다(기상연구소, 2007). 현재, 이러한 현상들을 가시화하고 대처방안을 마련하기 위한 일환으로 기후변화 시나리오(GCM)가 작성되어 연구에 이용되고 있다. 그러나 GCM의 경우, 공간적 해상도가 낮아 지형학적 특성 등을 충분히 반영하지 못하는 단점이 있어 최근에는 공간 해상도가 GCM보다 높은 RCM(Regional Climate Model, 지역기후모델)자료를 적용한 연구도 진행되고 있다. 본 논문에서는 SRES A2 온난화가스시나리오 기반의 기상청 RegCM3 RCM($27km{\times}27km$)로 부터 일(daily)단위 자료를 각각 모의하여 비교하고, BLRPM을 이용하여 일(daily)단위 자료를 시(hourly)단위로 분해(disaggregation)하였다. 그리고 이들을 이용하여 지속기간별 확률강우량을 산정하여 미래 기후변화가 극한 강우에 미치는 영향을 평가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.278-278
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• 2011

최근 우리나라는 기후변화 등으로 국지성호우가 발생하여 수공구조물의 피해 규모가 점점 커지고 있는 실정이다. 따라서 본 연구에서는 서울지점의 시자료를 이용하여 비정상성 강우빈도해석을 함으로써 기후변화를 고려한 확률강우량을 산정하였으며, 여러 시간분포방법을 비교, 분석하여 우이천유역과 같은 도시 하천의 강우분포 및 지형특성에 알맞은 강우의 시간분포 방법을 선정하고자 하였으며, 도시유출모형인 SWMM을 이용하여 비시나리오기반 기후변화에 따른 향후(2020~2030년) 재현기간 50년 빈도의 첨두유출량을 예측하였다. 분석결과 2020년의 경우 지속시간 1시간의 경우 Yen-Chow방법이 393.02CMS로 가장 높은 첨두 유출량을 보였으며, 지속시간 2시간, 3시간의 경우 Mononobe방법이 439.8149CMS, 503.5989CMS로 가장 높은 첨두 유출량을 나타내었다. 또한 2030년의 경우 지속시간 1시간의 경우 Yen-Chow방법이 416.75CMS로 가장 높았으며, 지속시간 2시간, 3시간의 경우 Mononobe방법이 470.13CMS, 533.7CMS로 가장 높은 첨두 유출량을 나타내었다.

• Journal of Korean Society of Forest Science
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• v.103 no.1
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• pp.105-112
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• 2014

The main purpose of this study is to measure spatio-temporal variation of forest tree volume based on the RCP(Representative Concentration Pathway) 8.5 scenario, targeting on Pinus densiflora forests which is the main tree species in South Korea. To estimate nationwide scale, $5^{th}$ forest type map and National Forest Inventory data were used. Also, to reflect the impact of change in place and climate on growth of forest trees, growth model reflecting the climate and topography features were applied. The result of the model validation, which compared the result of the model with the forest statistics of different cities and provinces, showed a high suitability. Considering the continuous climate change, volume of Pinus densiflora forest is predicted to increase from $131m^3/ha$ at present to $212.42m^3/ha$ in the year of 2050. If the climate maintains as the present, volume is predicted to increase to $221.92m^3/ha$. With the climate change, it is predicted that most of the region, except for some of the alpine region, will have a decrease in growth rate of Pinus densiflora forest. The growth rate of Pinus densiflora forest will have a greater decline, especially in the coastal area and the southern area. With the result of this study, it will be possible to quantify the effect of climate change on the growth of Pinus densiflora forest according to spatio-temporal is possible. The result of the study can be useful in establishing the forest management practices, considering the adaptation of climate change.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.14-14
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• 2015

공간보간기법은 미계측지역의 강수예측을 위해 통상적으로 사용되는 방법 중의 하나이다. 이 연구에서는 기상청에서 제공하고 있는 RCP 8.5 시나리오에 의한 남한상세 강수자료 중 지형이 복잡한 도서지역에서 제공되지 않는 데이터 누락격자에 대하여 최적의 공간보간기법을 선정하여 강수자료를 생성할 수 있도록 하였다. 적합한 보간기법을 선정하기 위해 데이터 누락지역에 대한 분석을 수행하였고, 최신 행정구역도에 맞추어 $1km{\times}1km$ 격자를 한반도 전체지역에 맞추어 생성된 격자를 사용하였다. ESRI사의 ArcGIS 프로그램을 이용하여 공간보간기법을 적용하였다. 사용된 보간법은 역거리가중치법(IDW), 정규크리깅(Ordinary Kriging), 보편크리깅(Universal Kriging), 스플라인(Spline)이며 가장 적합한 공간보간기법을 선정하기 위해 기후변화시나리오에 의한 데이터 중 해안선 주변 특정격자에서의 값을 누락시켜 공간보간기법을 통해 생성된 값과 기후변화 시나리오에 의한 값을 정량적으로 비교하였다. 공간보간기법의 적합도 평가를 위해 MAE(Mean Absolute Error), MSE(Mean Squared Error), PBIAS(Percent of BIAS), G(goodness of prediction) 분석을 수행하였고, 산점도 분석을 통해 실제값과 보간값의 오차율 평가를 병행하여 최적 공간보간기법을 결정하였다. 사용된 강수데이터는 RCP 8.5 시나리오에서 2015~2019년 중 강수가 높게 나타난 8월 자료를 이용하였다. 해안선 지역의 강수량 추정시 역거리 가중치법과 크리깅방법은 일부 지점에서 과다 추정되는 경향이 있고, 스플라인 방법이 전체적인 총 강수량이 기후변화시나리오에 의한 실제값과 유사한 것으로 나타났다. 실제값과 보간값의 교차검증을 수행한 결과 정규크리깅 기법이 가장 높은 정확도를 보였으며, 전체적으로 실제값과 유사한 범위내의 강수량이 생성되는 것으로 나타났다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.323-337
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• 1999

Seafloor morphology and manganese nodule occurrence were studied in the Korea Deep-sea Environmental Study (KODES) area, northeast equatorial Pacific, to understand their relationship. Study area is composed of three elongated valleys and hills with about 100~200 m height along NNE-SSW direction. Valley region is generally flat. However, hill region is very rugged with big cliffs of about 100m height and small depressions of several tens of meters depth. Tectonic movement along the Clarion-Clipperton fracture zone, consequent formation of elongated abyssal hills and Valleys, erosion of siliceous bottom sediments by bottom currents, and dissolution of carbonate sediments on the abyssal hills below CCD result in the rugged morphology. Manganese nodule occurrence is closely related to the morphology of the study area; mostly rounded-shaped manganese nodules with about 5 cm diameter are abundant on the flat valley region, whereas irregular shaped nodules (or manganese crust) with less than 5 cm to about 1 m diameter occur on the hill. These results supports the previous reports that nodule abundance, composition, and morphology are variable both on regional and local small scales on the seafloor even within some abundant nodule provinces depending on oceanographic characteristics such as bathymetric features, surface sediment type, sediment thickness, and so on. We suggest that such oceanographic characteristics affect interrelatedly on the formation of manganese nodules, and tectonic movement of the Pacific plate ultimately constrain the nodule occurrence. A potential mining place in the KODES area seems to be the valley region, which is elongated to the NNW-SSE direction with 3-4 km width.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.98-98
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• 2021

동역학파 기반 순간단위도 (Dynamic wave-based Instantaneous Unit Hydrograph)를 이용하여 유역에서의 강우에 의한 유출을 예측하는 기법을 개발하였으며, 국내 실제 자연 유역에 적용하여 기법의 타당성과 적용성을 검증하였다. 본 연구에서 제시한 '동역학파 기반 순간단위도 방법'은 물리기반 수치모형인 동역학파 강우유출모형과 개념적 순간단위도 방법을 결합하여 사용함으로써 물리적으로 정확하면서도 빠르고 안정적으로 강우-유출을 예측하는 것을 목적으로 한다. 유역의 순간단위도는 유역의 지형, 조도계수와 동역학파 강우유출모형인 tRIBS-OFM을 이용하여 계산된 S-수문곡선을 수치적으로 미분함으로써 유도되며, 유도된 순간단위도는 강우강도에 따라 변화하므로 회선적분을 통한 유출수문곡선 예측 시 강우-유출 관계의 비선형성을 고려할 수 있다. 본 연구에서 유도된 순간단위도의 첨두 값과 첨두 발생시간은 강우강도 값과 각각 양과 음의 상관관계를 가졌으며 강우강도 값과 멱 함수 (power function)의 관계를 가졌다. 이는 Paik and Kumar (2004) 등 기존 연구들에서 밝힌 순간단위도의 특성과 일치하였으며, 본 연구에서는 더 나아가 멱함수의 지수를 산정한 후 임의의 강우강도 값에 대응하는 순간단위도를 멱함수 관계를 이용하여 보간할 수 있는 방법을 제시하였다. 실제 유역에 대한 적용은 강원도 인제군에 위치한 내린천 유역을 대상으로 수행하였다. 유역을 여러 개의 소유역으로 분할하여 강우의 공간적 분포를 고려하였으며, 각 소유역에서의 유출량을 동역학파 기반 순간단위도를 이용해 계산한 뒤 물리기반의 하도추적모형을 이용하여 전체 유역에서의 유출수문곡선을 예측했다. 예측된 유출수문곡선을 관측 유출 자료와 비교해본 결과 NSE (Nash-Sutcliffe model efficiency coefficient)가 0.6 이상으로 측정되어 적절히 유출을 예측한 것으로 판단되었다.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.1
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• pp.3-9
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• 2013

Development of housing, industrial and public lands has been a cause to increase a temperature of a city higher than that of a rural area. Knowing that, the research analyzed temperature changes in a riverside district and a coastal area depending on the land usage and climate change in the areas. Add to this, the study examined a correlation between topographic characteristics and temperature changes. According to the results, the temperature was increased by $1.80^{\circ}C$ in 2007 comparing to 2003 while the wind velocity was reduced by 0.24m/s. In addition, a more number of areas were designated as build-up areas which, in return, decreased the forested land. The analysis on the correlation reported that the riverside district has more of grassland and bare land while the coastal area has more of wooded land and grassland. The study is expected to be used as fundamental data for research on heat island effect which would be different by each regional characteristic as it proposes measures to solve the heat island effect.