• Journal of the Korean Geographical Society
• /
• v.51 no.6
• /
• pp.761-777
• /
• 2016

This study is to suggest landform and environmental problems of border region of N. Korea and China by analyzing results of field work for the Dumangang and the Amnokgang from year 2000 up to year 2016. By the social system in North korea, access of study material is possible with satellite image and published statistical data, but impossible direct data collection. We gathered field work data on landform and environment in border Region of N. Korea and China. Before field survey, we analysed geometrical landform and geology using DEM and digital geology map. We analyzed landform and environmental problems occurring in upper, midstream, and downstream region of the Dumangang and the Amnokgang using field work data. Resultingly, this study will be expected to support as basic data for resonable management on natural resources and empirical research activities on North Korea.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.194-199
• /
• 2006

쌍천유역의 강수량과 지하수위의 관계를 분석한 결과 융설효과를 확인하였고 갈수기에 지하수위가 현저히 저하됨을 확인하였다. 쌍천유역의 지하수위와 GOI의 상관관계를 분석한 결과 70일 이동평균값을 이용한 GOI가 가장 높은 상관관계를 보여주었다. 융설효과를 고려하기 위해서 먼저 유역의 DEM 자료를 이용하여 100m 간격으로 고도별 면적분포를 구하고 기온이 100m당 $0.5^{\circ}C$씩 감소하는 것을 고려하여 강수사상이 발생하면 $0^{\circ}C$ 이하가 되는 고도에서는 강설사상이 발생하는 것으로 가정하였다. 이 때 고도별 면적분포에서 구해지는 면적비를 고려하여 강수사상을 강우와 강설로 나누었다. 이후에 고도를 고려한 기온이 $0^{\circ}C$ 이상인 날에 그 고도의 설적이 모두 녹는 것으로 가정하였고 강우가 발생한 것으로 처리하였다. 유역평균 일최대침투량을 알아내기 위하여 강수량자료를 일정값 이상은 고정하여 수정된 강수량자료로 70일 이동평균값을 구하고 이 값들과 지하수위와의 상관관계를 분석해 본 결과 40mm가 일최대침투량으로 가정하였을 때 가장 높은 상관관계를 보여주었다. 쌍천유역의 경우 40mm가 한계침투량이다. 이렇게 수정된 강수자료를 이용하여 이동평균을 구하여 지하수위와의 상관관계를 구해본 결과 쌍천유역의 2003년부터 2005년까지 2개년 자료에 대해서 융설을 고려했을 때 상관관계가 더 높아짐을 알 수 있고 한계침투량을 고려했을 때도 상관관계가 더 높아짐을 알 수 있으며 융설효과와 한계침투량을 동시에 고려했을 경우에 가장 높은 상관관계를 얻을 수 있었다.$2.8g/cm^3$로 가정했을 때, 경상분지의 화강암류의 압력평균값이 약 $0.73{\sim}3.16kbar$의 범위를 가졌고, 경상분지내 백악기 화강암류의 정치 깊이는 $2.6{\sim}11.4km$범위를 가졌다. 이는 경상분지 화강암류에 대해 유추된 기존의 정성적인 생각과 일치한다는 것을 알 수 있었고, 각섬석의 $Al^T$함량을 이용한 여러 경험적, 실험적인 압력계가 많은 제한점이 있지만 경상분지의 백악기 불국사화강암류에는 정성적으로 유효함을 알 수 있었다. 우리는 최종적으로 경상분지내 백악기 화강암류는 천부관입 암체이고 노출된 화강암류가 천부지각이라는 것을 알 수 있었다. 것이 아니라 낙관적 예측을 수행하는 경향이 있음을 발견할 수 있었다.원밭, 화산회밭으로 6개 유형으로 분류할 경우 각각의 분포면적은 41.9%, 23.3%, 17.5%, 13.9%, 1.1. 2.2% 이었다. 도시화 및 도로확대 등 다양한 토지이용 및 지형개변으로 과거의 토양정보가 많이 변경되었다. 그래서, 앞으로는 인공위성자료 및 항공사진을 이용하여 빠르고 쉽게 활용할 수 있는 토양조사 방법개발과 기 구축된 토양도의 수정, 보완 작업이 필요한 절실히 요구되고 있는 현실이다.브로 출시에 따른 마케팅 및 고객관리와 관련된 시사점을 논의한다.는 교합면에서 2, 3, 4군이 1군에 비해 변연적합도가 높았으며 (p < 0.05), 인접면과 치은면에서는 군간 유의차를 보이지 않았다 이번 연구를 통하여 복합레진을 간헐적 광중합시킴으로써 변연적합도가 향상될 수 있음을 알 수 있었다.시장에 비해 주가가 비교적 안정적인

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.23 no.4
• /
• pp.153-178
• /
• 2018

Most operational uses of wind speed data require measurements at, or estimates generated for, the reference height of 10 m above mean sea level (AMSL). On the Ieodo Ocean Research Station (IORS), wind speed is measured by instruments installed on the lighthouse tower of the roof deck at 42.3 m AMSL. This preliminary study indicates how these data can best be converted into synthetic 10 m wind speed data for operational uses via the Korea Hydrographic and Oceanographic Agency (KHOA) website. We tested three well-known conventional empirical neutral wind profile formulas (a power law (PL); a drag coefficient based logarithmic law (DCLL); and a roughness height based logarithmic law (RHLL)), and compared their results to those generated using a well-known, highly tested and validated logarithmic model (LMS) with a stability function (${\psi}_{\nu}$), to assess the potential use of each method for accurately synthesizing reference level wind speeds. From these experiments, we conclude that the reliable LMS technique and the RHLL technique are both useful for generating reference wind speed data from IORS observations, since these methods produced very similar results: comparisons between the RHLL and the LMS results showed relatively small bias values ($-0.001m\;s^{-1}$) and Root Mean Square Deviations (RMSD, $0.122m\;s^{-1}$). We also compared the synthetic wind speed data generated using each of the four neutral wind profile formulas under examination with Advanced SCATterometer (ASCAT) data. Comparisons revealed that the 'LMS without ${\psi}_{\nu}^{\prime}$ produced the best results, with only $0.191m\;s^{-1}$ of bias and $1.111m\;s^{-1}$ of RMSD. As well as comparing these four different approaches, we also explored potential refinements that could be applied within or through each approach. Firstly, we tested the effect of tidal variations in sea level height on wind speed calculations, through comparison of results generated with and without the adjustment of sea level heights for tidal effects. Tidal adjustment of the sea levels used in reference wind speed calculations resulted in remarkably small bias (<$0.0001m\;s^{-1}$) and RMSD (<$0.012m\;s^{-1}$) values when compared to calculations performed without adjustment, indicating that this tidal effect can be ignored for the purposes of IORS reference wind speed estimates. We also estimated surface roughness heights ($z_0$) based on RHLL and LMS calculations in order to explore the best parameterization of this factor, with results leading to our recommendation of a new $z_0$ parameterization derived from observed wind speed data. Lastly, we suggest the necessity of including a suitable, experimentally derived, surface drag coefficient and $z_0$ formulas within conventional wind profile formulas for situations characterized by strong wind (${\geq}33m\;s^{-1}$) conditions, since without this inclusion the wind adjustment approaches used in this study are only optimal for wind speeds ${\leq}25m\;s^{-1}$.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.2
• /
• pp.208-225
• /
• 2019

To understand the mean surface circulation and surface currents in the East Sea, trajectories of surface drifters passed through the East Sea from 1991 to 2017 were analyzed. By analyzing the surface drifter trajectory data, the main paths of surface ocean currents were grouped and the variation in each main current path was investigated. The East Korea Warm Current (EKWC) heading northward separates from the coast at $36{\sim}38^{\circ}N$ and flows to the northeast until $131^{\circ}E$. In the middle (from $131^{\circ}E$ to $137^{\circ}E$) of the East Sea, the average latitude of the currents flowing eastward ranges from 36 to $40^{\circ}N$ and the currents meander with large amplitude. When the average latitude of the surface drifter paths was in the north (south) of $37.5^{\circ}N$, the meandering amplitude was about 50 (100) km. The most frequent route of surface drifters in the middle of the East Sea was the path along $37.5-38.5^{\circ}N$. The surface drifters, which were deployed off the coast of Vladivostok in the north of the East Sea, moved to the southwest along the coast and were separated from the coast to flow southeastward along the cyclonic circulation around the Japan Basin. And, then, the drifters moved to the east along $39-40^{\circ}N$. The mean surface current vector and mean speed were calculated in each lattice with $0.25^{\circ}$ grid spacing using the velocity data of surface drifters which passed through each lattice. The current variance ellipses were calculated with $0.5^{\circ}$ grid spacing. Because the path of the EKWC changes every year in the western part of the Ulleung Basin and the current paths in the Yamato Basin keep changing with many eddies, the current variance ellipses are relatively large in these region. We present a schematic map of the East Sea surface current based on the surface drifter data. The significance of this study is that the surface ocean circulation of the East Sea, which has been mainly studied by numerical model simulations and the sea surface height data obtained from satellite altimeters, was analyzed based on in-situ Lagrangian observational current data.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.6
• /
• pp.587-601
• /
• 2020

The ocean circulation was simulated in the East Sea and Ulleungdo-Dokdo region using ROMS (Regional Ocean Modeling System) model. By adopting the East Sea 3 km model and the HYCOM 9 km data, Ulleungdo 1 km model and Ulleungdo-Dokdo 300 m model were constructed with one-way grid nesting method. During the model development, a correction method was proposed for the distortion of the open boundary data which may be caused by the bathymetry data difference between the mother and child models and the interpolation/extrapolation method. Using this model, a super-high resolution ocean circulation with a horizontal resolution of 300 m near the Ulleungdo and Dokdo region was simulated for year 2018. In spite of applying the same conditions except for the initial and boundary data, the numerical models result indicated significantly different characteristics in the study area. Therefore, these results were compared and verified by using the surface current data estimated by satellites altimeter data and temperature data from NIFS (National Institute of Fisheries Science). They suggest that in general, the improvement of the one-way grid nesting with the HYCOM data on RMSE, Mean Bias, Pattern correlation and Vector correlation is greater in 300 m model than in the 1 km model. However, the nesting results of using East Sea 3 km model showed that simulations of the 1 km model were better than 300 m model. The models better resolved distinct ridge/trough structures of isotherms in the vertical sections of water temperature when using the higher horizontal resolution. Furthermore, Karman vortex street was simulated in Ulleungdo-Dokdo 300 m model due to the terrain effect of th islands that was not shown in the Ulleungdo 1 km model.