• Journal of the Korean Society of Environmental Restoration Technology
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• v.15 no.1
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• pp.63-71
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• 2012

To investigate the air temperature difference between windward and leeward side at high-rise building area, the air temperature and relative humidity data were observed for 10 minute interval from July 9, 2011 to November 30, 2011. The observed data were compared, analyzed and examined to illustrate air temperature between windward side (H Apartment) and Leeward side (W Apartment). The diurnal and seasonal variation of air temperature difference between windward and leeward site were also investigated. After the analysis, the overheat of windward side by $0.4^{\circ}C$ irrespective short distance of two observation positions. It was also lower than those of surrounding air temperature observing stations. It is mainly due to the air temperature decreasing effects of leeward side of high rise buildings.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.1
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• pp.30-35
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• 2003

The study of the scars formed on the bark of pine trees damaged by forest fire was carried out in the burned area of Samchuk and Donghae in 2000. Fire scars were formed on the bark of trees when fire passed by the tree. Fire scarring is usually found on the windward and leeward sides of the tree. Fire spread was analyzed topographically using the fire scars formed at the tree stem. Fire spread was closely related to the shape, slope and direction of the forestland. Four fire direction types are classified according to the shapes of the forestland. The height of the fire scar was higher on the leeward side than on the windward side of the trees studied. The burnt area of the total bark of the tree was over 30% in dead trees and below 12% in living trees. The regression model of the burnt stem area using the height of the fire scar, the diameter of breast height and the height of tree was Y=-2.484${\times}$Height＋0.04199${\times}$D.B.H-1.686${\times}$Windward＋11.172${\times}$Leeward＋23.432(r=0.936, F=409.968, P＞0.0001).

• Journal of Environmental Impact Assessment
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• v.19 no.6
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• pp.583-590
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• 2010

To determine nocturnal inversion characteristics at the leeward side of high-rise building, air temperature data were observed at 10 minute interval from February 22, 2010 to April 15, 2010. The observed data were compared, analyzed and examined to illustrate air temperature differences between the roof (XAR) and surface (XAG) of X apartment. The wind speed, wind direction and precipitation data were also observed at XAR and YJL (Yangjae Stream) sites at the same time. After the analysis, the maximum nocturnal inversion was observed by $4.0^{\circ}C$ at 3:40, 3:50, 4:10 on February 24th 2010, at that time the weather condition was clear and weak wind. Air temperature inversions at the leeward side of high-rise building were observed on whole day in wintertime and air temperature inversion intensity was also higher than other nearby area (SMG).

• Journal of Ecology and Environment
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• v.37 no.2
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• pp.91-97
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• 2014

Little is known about how the increased porosity of a deciduous windbreak, which results from loss of leaves, influences wind speed reduction. We hypothesized that, with loss of foliage, the wind speed reduction effectiveness of a deciduous windbreak decreases on near leeward side but not on further leeward side and that wind speed recovers faster in the full foliage season than in other seasons. During summer, autumn, and winter (full, medium, and non-foliage season, respectively), we observed wind speed and direction around a deciduous windbreak in a traditional Korean village on windward and near and further leeward sides (at -8H, 2H, and 6H; H = 20 m, a windbreak height). We used a linear mixed effects model to determine that the relative wind speed reduction at 2H significantly decreased from 83% to 48% ($F_{2,111.97}=73.6$, P < 0.0001) with the loss of foliage. However, the relative wind speed reduction at 6H significantly increased from 26% to 43% ($F_{2,98.54}=18.5$, P < 0.0001). Consequently, wind speed recovery rate between 2H and 6H in summer was two times higher than in autumn and ten times higher than in winter ($F_{2,102.93}=223.1$, P < 0.0001). These results indicate that deciduous windbreaks with full foliage seem to induce large turbulence and increase wind speed recovery rate on leeward side. Our study suggests that further research is needed to find the optimal foliage density of a deciduous windbreak for maximizing windbreak effectiveness regardless of seasonal foliage changes.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.169-180
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• 2019

The underlying mechanism of the wind-induced vibration of the hangers of the suspension bridges is still not fully understood at present and hence is comprehensively examined in this study. More specifically, a series of field measurements on the No. 2 hanger of the Xihoumen Bridge was first carefully conducted. Large amplitude vibrations of the hanger were found and the oscillation amplitude of the leeward cable was obviously larger than that of the windward cables. Furthermore, the trajectory of the leeward cable was close to an ellipse, which agreed well with the major characteristics of wake-induced vibration. Then, a theoretical model for the wake-induced vibration based on a 3-D continuous cable was established. To obtain the responses of the leeward cable, the finite difference method (FDM) was adopted to numerically solve the established motion equation. Finally, numerical simulations by using the structural parameters of the No. 2 hanger of the Xihoumen Bridge were carried out within the spatial range of $4{\leq}X{\leq}10$ and $0{\leq}Y{\leq}4$ with a uniform interval of ${\Delta}X={\Delta}Y=0.25$. The results obtained from numerical simulations agreed well with the main features obtained from the field observations on the Xihoumen Bridge. This observation indicates that the wake-induced vibration might be one of the reasons for the hanger oscillation of the suspension bridge. In addition, the effects of damping ratio and windward cable movement on the wake-induced vibration of the leeward cable were numerically investigated.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.153-156
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• 2008

Comparative analysis of forest fire danger rating on the forest characteristics of thinning area and non-thinning area on forest fire burnt area was studied in this work. To investigate the effect of thinning slash in forest fire, Gangneung-si Wangsan-myeon, Ulgin-gun Wonnam-Myeon, Samchok-si Gagok-Myeon, in which forest fire broke out, were selected. As a result that investigated forest fire danger ratio between thinning slash and non-thinning slash, leeward scorching ratio(36%), crown damage ratio(29%), mortality of branch at the former are higher than those at the latter, leeward scorching ratio of tree, where thinning slash is around, is 10%-20% higher than that of independent tree. So I estimate that thinning slash has a some effect on the intensity of forest fire. And the result to investigate damage of forest fire according to tree species shows that leeward scorching ratio of conifer is 5% higher than that of non-conifer, and mortality of branch of the former is 19% higher than that of the latter. It is considered that forest fire may affect directly to a tree trunk if it diffuse to piled thinning tree because there was no space between thinning trees and trees. Furthermore, it was found that re-ignition had a chance to occur due to lots of piled thinning trees.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.277-285
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• 2019

This study was conducted to understand the growth characteristics of Picea jezoensis that was one of representative subalpine species in Korea, in the light of the effects of wind and micro-topography in its habitats on Mt. Deogyu, Korea. The prevailing wind directions were southwest and west at the study sites. We randomly selected P. jezoensis (height ≥ 1.5 m) on windward, intermediate, and leeward slopes and measured diameter at breast height (DBH), height, crown length by 8 directions in upper, middle and lower sectors of the crown. We examined the micro-topography of P. jezoensis stood on and classified it into 3 types: type 1 was mounded and fully exposed to surrounding environments without neighboring trees; type 2 was somewhat wind-protected by surrounding rocks, but no neighboring vegetation; type 3 was on gentle slope or flat where P. jezoensis grew with neighboring trees or shrubs. The ratios of height to DBH, and estimated crown growth to actual crown growth (hereafter crown growth ratio) were compared among the three types of micro-topography on windward, intermediate and leeward sites. The height growth per DBH and crown growth ratio in the upper and middle crowns were the smallest on the windward site, and the highest on the leeward site (p < 0.01). The crown growth ratio on type 1 on the windward site was only 46% of that on type 3 on the leeward site. Although on the same windward slope, trees on type 1 had more deformed crown shapes than that on Type 3, showing asymmetric crown cross-sectional areas. Wind and micro-topography played critical roles on the crown growth of P. jezoensis.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.2
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• pp.47-52
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• 2002

In this study, in order to find out relationship of green space distribution and lower air temperature effect, observed air temperature distribution in and out green space in the cloudy. On basis of the result, we are analyzed relationship of air temperature distribution in and out green space, of green space distribution and air temperature of, lower air temperature effect and the urban in between the green space by using regression analysis. According to the result, the higher temperature zone formed around urban, and the lower temperature zone was similar to shape of green space. In case of the green space, higher temperature zone is formed around paved surface and barren ground, lower temperature zone is done forest and water area. To compare air temperature of windward and leeward around green space, the windward formed the lower temperature zone and although the wind direction is not the leeward to the green space, air temperature formed lower temperature zone to the urban in between the green space.

• Journal of Forest and Environmental Science
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• v.33 no.4
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• pp.348-354
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• 2017

Agroforestry has been practiced in arid and semi-arid regions for the purposes of preventing desertification and to increase income for locals. However, the intended effects of such practices have been limited due to strong winds and aridity. This study undertook multi-year monitoring of the productivity of income crops associated with windbreak planting in a semi-arid region of Mongolia, and explored strategies of windbreak planning to enhance the multi-purpose effects of agroforestry practices. The tree crown density of windbreak planting was on average 40% in one year after planting and 65% 2-3 years after, and thereby windspeeds were reduced by about 30% and 54%, respectively. Average windspeed reductions at leeward distances from the windbreak planting were approximately 60% within 3H (H=tree height), 50% at 5H, and 42% at 7-9H, presenting a pattern in which the farther the distance the less the reduction in windspeeds. The windbreak planting increased crop productivity by up to 6.8 times, compared to the productivity absent of windbreaks. Increases in the crown density as stated above resulted in increases of crop productivity by up to 3.6 times. Based on such results, this study proposed a model of windbreak planning as a typical land-use system of border windbreak planting or alternate windbreak planting of combining trees and income crops. The model also included tree planting with a crown density of 60% and allocation of income crops within a leeward distance of 5 times the height of the trees to reduce windspeeds by about 50%. The results from this study are applicable to practicing agroforestry not only at the study site but also in other regions worldwide where strong winds and aridity are problematic.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.447-448
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• 2006