• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.143-156
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• 2015

In order to understand the dynamic characteristics of water column environments in the Western Pacific seamount area (approximately $150.2^{\circ}E$, $20^{\circ}N$), we investigated the water mass and the behavior of water column parameters such as dissolved oxygen, inorganic nutrients (N, P), and chlorophyll-a. Physico-chemical properties of water column were obtained by CTD system at the nine stations which were selected along the east-west and south-north direction around the seamount (OSM14-2) in October 2014. From the temperature-salinity diagram, the main water masses were separated into North Pacific Tropical Water and Thermocline Water in the surface layer, North Pacific Intermediate Water in the intermediate layer, and North Pacific Deep Water in the bottom layer, respectively. Oxygen minimum zone (OMZ, mean $O_2$ $73.26{\mu}M$), known as dysoxic condition ($O_2<90{\mu}M$), was distributed in the depth range of 700~1,200 m throughout the study area. Inorganic nutrients typified by nitrite + nitrate and phosphate showed the lowest concentration in the surface mixed layer and then gradually increased downward with representing the maximum concentration in the OMZ, with lower N:P ratio (13.7), indicating that the nitrogen is regarded as limiting factor for primary production. Vertical distribution of water column parameters along the east-west and south-north station line around the seamount showed the effect of bottom water inflowing at around 500 m deep in the western and southern region, and concentrations of water column parameters in the bottom layer (below 2,500 m deep) of the western and southern region were differently distributed comparing to those of the other side regions (eastern and northern). The value of Excess N calculated from Redfield ratio (N:P=16:1) represented the negative value throughout the study area, which indicated the nitrogen sink dominant environments, and relative higher value of Excess N observed in the bottom layer of western and southern region. These observations suggest that the topographic features of a seamount influence the circulation of bottom current and its effects play a significant role in determining the behavior of water column environmental parameters.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.233-241
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• 2016

Experiments were carried out to quantify the topographic effects on attenuation of sunshine in complex terrain and the results are expected to help convert the coarse resolution sunshine duration information provided by the Korea Meteorological Administration (KMA) into a detailed map reflecting the terrain characteristics of mountainous watershed. Hourly shaded relief images for one year, each pixel consisting of 0 to 255 brightness value, were constructed by applying techniques of shadow modeling and skyline analysis to the 3m resolution digital elevation model for an experimental watershed on the southern slope of Mt. Jiri in Korea. By using a bimetal sunshine recorder, sunshine duration was measured at three points with different terrain conditions in the watershed from May 15, 2015 to May 14, 2016. The brightness values of the 3 corresponding pixel points on the shaded relief map were extracted and regressed to the measured sunshine duration, resulting in a brightness-sunshine duration response curve for a clear day. We devised a method to calibrate this curve equation according to sky condition categorized by cloud amount and used it to derive an empirical model for estimating sunshine duration over a complex terrain. When the performance of this model was compared with a conventional scheme for estimating sunshine duration over a horizontal plane, the estimation bias was improved remarkably and the root mean square error for daily sunshine hour was 1.7hr, which is a reduction by 37% from the conventional method. In order to apply this model to a given area, the clear-sky sunshine duration of each pixel should be produced on hourly intervals first, by driving the curve equation with the hourly shaded relief image of the area. Next, the cloud effect is corrected by 3-hourly 'sky condition' of the KMA digital forecast products. Finally, daily sunshine hour can be obtained by accumulating the hourly sunshine duration. A detailed sunshine duration distribution of 3m horizontal resolution was obtained by applying this procedure to the experimental watershed.

• Journal of Korea Water Resources Association
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• v.52 no.11
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• pp.917-929
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• 2019

Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.103-113
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• 2023

The river confluence is a section in which two rivers with different topographical and hyrodynamic characteristics are combined into one, and it is a section in which rapid flow, inflow of sediments, and hydrological topographic changes occur. In the confluence section, the flow of fluid occurs due to the difference in density due to the type of material or temperature difference, which is called a density flow. It is necessary to accurately measure and observe the confluence section including a certain section of the main stream and tributaries in order to understand the mixing behavior of the water body caused by the density difference. A comprehensive analysis of this water mixture can be obtained by obtaining flow field and flow rate information, but there is a limit to understanding the mixing of water bodies with different physical properties and water quality characteristics of rivers flowing with stratigraphic flow. Therefore, this study attempts to grasp the density flow through the water temperature distribution in the confluence section. Among the extensive data of the river, vertical data and water surface data were acquired, and through this, the stratification phenomenon of the confluence was to be confirmed. It was intended to analyze the mixed pattern of the confluence by analyzing the water mixing pattern according to the water temperature difference using the vertical data obtained by measuring the repair volume by installing the ADCP on the side of the boat and measuring the real-time concentration using YSI. This study can supplement the analysis results of the existing water quality measurement in two dimensions. Based on the comparative analysis, it will be used to investigate the current status of stratified sections in the water layer and identify the mixing characteristics of the downstream section of the river.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.3
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• pp.32-45
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• 2014

The study attempts to interpret original location and landscape composition of Yowol-pavilion Garden under the premise that tablet and poetry are important criteria for inference of unique location and landscape composition of a pavilion garden. The study raises the meaning, status, and value of Yowol Pavilion Garden as a cultural asset. The results of the study are as follows. First, Yowol-pavilion Garden was a place where famous Confucius scholars in Joseon Dynasty in 16th Century, including Kim, Kyung-Woo, the owner of the garden, used to share the taste for the arts and poetries with their colleagues. Along with a main characteristic of Yowol Pavilion Garden as a hideout for the Confucius scholars who stayed away from a political turmoil, the new place characteristic of the garden, a bridgehead for the formation of regional identity, was discovered in the record of "Joseon-Hwanyeo-Seungram Honam-Eupji JangSeong-Eupji", As described in "The first creative poetry of Yowol-pavilion", the intention for the creation of Yowol-pavilion Garden and the motive for its landscape composition is interpreted as a space of rivalry where the world, reality and ideals are mixed up. Second, related to outstanding scenic factors and natural phenomena when taking a view from the pavilion, the name of the house 'Yowol', which means 'Greeting the moon rising on the Mt. Wolbong' is the provision of nature and taste for the arts, and is directly connected to the image of leaving the worldly. In other words, the name was identified to be the one that reflected the intention for landscape composition to follow the provision of nature separating from joy and sorrow of the mundane world. Third, as for the location, it was confirmed through "YeongGwang-Soksu-Yeoji-Seungram" that Yowol-pavilion Garden was a place where the person who made the pavilion prepared for relaxation after stepping down from a government post, and literature and various poetry show that it was also a place of outstanding scenic where Yellow-dragon River meandered facing Mt. Wolbong. Especially, according to an interview with a keeper, the visual perception frequency of the nightscape of Yowol-pavilion Garden is the highest when viewing by considering the east, the direction of Yellow-dragon River, as Suksigak[normal angle's view], towards Yowel-pavilion from the keeper's house. In addition, he said that the most beautiful landscape with high perception strength is when the moon came up from the left side of Yowol-pavilion, cuts across the Lagerstroemia india heal in front of Yowol-pavilion, and crosses the meridian between Mt. Wolbong peaks facing Yowol-pavilion. Currently, the exposure of Yowol-pavilion Garden is $SE\;141.2^{\circ}$, which is almost facing southeast. It is assumed that the exposure of Yowol-pavilion Garden was determined considering the optimized direction for appreciating the trace of the moon and the intention of securing the visibility as well as topographic conditions. Furthermore, it is presumed that the exposure of Yowol-pavilion Garden was determined so that the moon is reflected on the water of Yellow-dragon River and the moon and its reflection form a symmetry. Fourth, currently, Yowol-pavilion Garden is divided into 'inner garden sphere' composed of Yowol-pavilion, meeting place of the clan and administration building, and 'outer garden sphere' which is inclusive of entrance space, Crape Myrtle Community Garden and Pine Tree Forest in the back. Further, Yowol-pavilion Garden has been deteriorated as the edge was expanded to 'Small lake[Yong-so] and Gardens of aquatic plants sphere' and recently-created 'Yellow-dragon Pavilion and park sphere'. Fifth, at the time it was first made, Yowol-pavilion Garden was borderless gardens consisting of mountains and water taking a method of occupying a specific space of nearby nature centering around pavilion by embracing landscape viewed from the pavilion, but interpreted current complex landscapes are identified to be entirely different from landscapes of the original due to 'Different Changes', 'Fragmentation' and 'Apart piece' in many parts. Lastly, considering that Yowol-pavilion Garden belongs to the Cultural Properties Protection Zone, though not the restoration to the landscapes of the original described in tablet and literature record, at least taking a measure from the aspect of land use for minimizing adverse effect on landscape and visual damage is required.