• Ocean and Polar Research
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• 제31권4호
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• pp.297-304
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• 2009

We investigated the response of the westerly winds over the Southern Ocean (SO) to glacial boundary conditions for the Last Glacial Maximum using the CCM3 atmospheric general circulation model. In response to glacial boundary conditions, the zonally averaged maximum SO westerly winds weakened 20-35% and were displaced toward the equator by 3-4 degrees. This weakening of the SO westerly winds arose from a substantial increase in mean sea level pressure (MSLP) in the southern part of the SO around Antarctica relative to the northern part. The increase in MSLP around Antarctica is associated with a marked temperature reduction caused by an increase in sea ice cover and ice albedo feedback during the glacial time. The weakened westerly winds in the SO and their equator-ward displacement might play a role in reducing the atmospheric $CO_2$ concentration by reducing upwelling of the carbon rich deep water during the glacial time.

• Wind and Structures
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• 제24권6호
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• pp.637-656
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• 2017

In Japan, at least 28 local winds are known by name, most of them associated with downslope windstorms and gap winds. To review these windstorms, we categorize them based largely on the atmospheric conditions and formation mechanisms, and then focus on representative examples. These representative cases include the "Yamaji­kaze", a typical downslope windstorm, the "Hirodo-­kaze", a downslope windstorm induced by a nearby typhoon (intense tropical cyclone), and the "Karak-kaze", a downslope wind with a clear diurnal variation. Other downslope winds such as the "Inami-kaze" and the gap wind "Kiyokawa­dashi" are also described. Among these winds, the "Yamaji-kaze", "Hirodo-kaze", and "Kiyokawa-dashi" are considered the three most notorious due to their destructive power. After describing and comparing these winds, we discuss remaining issues to be considered in future studies.

• Wind and Structures
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• 제6권3호
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• pp.179-196
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• 2003

A long suspension bridge is often located within a unique wind environment, and strong winds at the site seldom attack the bridge at a right angle to its long axis. This paper thus investigates the buffeting response of long suspension bridges to skew winds. The conventional buffeting analysis in the frequency domain is first improved to take into account skew winds based on the quasi-steady theory and the oblique strip theory in conjunction with the finite element method and the pseudo-excitation method. The aerodynamic coefficients and flutter derivatives of the Tsing Ma suspension bridge deck under skew winds, which are required in the improved buffeting analysis, are then measured in a wind tunnel using specially designed test rigs. The field measurement data, which were recorded during Typhoon Sam in 1999 by the Wind And Structural Health Monitoring System (WASHMS) installed on the Tsing Ma Bridge, are analyzed to obtain both wind characteristics and buffeting responses. Finally, the field measured buffeting responses of the Tsing Ma Bridge are compared with those from the computer simulation using the improved method and the aerodynamic coefficients and flutter derivatives measured under skew winds. The comparison is found satisfactory in general.

• Wind and Structures
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• 제38권4호
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• pp.277-293
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• 2024

The recorded thunderstorm winds at a point contain tri-directional components. The probabilistic characteristics of such recorded winds in terms of instantaneous mean wind speed and direction, and the probability distribution and the time-frequency dependent crossed and non-crossed power spectral density functions for the high-frequency fluctuating wind components are unclear. In the present study, we analyze the recorded tri-directional thunderstorm wind components by separating the recorded winds in terms of low-frequency time-varying mean wind speed and high-frequency fluctuating wind components in the alongwind direction and two orthogonal crosswind directions. We determine the time-varying mean wind speed and direction defined by azimuth and elevation angles, and analyze the spectra of high-frequency wind components in three orthogonal directions using continuous wavelet transforms. Additionally, we evaluate the coherence between each pair of fluctuating winds. Based on the analysis results, we develop empirical spectral models and lagged coherence models for the tri-directional fluctuating wind components, and we indicate that the fluctuating wind components can be treated as Gaussian. We show how they can be used to generate time histories of the tri-directional thunderstorm winds.

• 한국해양학회지:바다
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• 제8권3호
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• pp.262-273
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• 2003

기상청에서 현업 예보용으로 사용되는 중규모 기상 모델(MM5/KMA)의 해상풍 예측 결과와 이를 입력 자료로 제 3세대 파랑 모델(WAVEWATCH-III)을 적용하여 2002년 1년 동안의 한반도 주변해역의 해상풍과 파랑 특성을 분석하였다. 모델 결과의 검증을 위해서 해양기상 관측 부이의 관측 자료와 TOPEX/POSEIDON위성의 유의 파고 자료를 이용한 통계 비교 분석을 실시하였다. 관측 값과 모델 결과 사이에 약 60-80%의 상관성을 나타내었고, 연안에 가장 근접해 위치한 칠발도의 풍향을 제외하면, 연안 지역까지의 해상풍과 파고를 본 모델에서 잘 재현하고 있다고 분석되었다. 위의 검증 결과를 토대로 2002년 한반도를 포함한 동아시아 해역의 월평균 해상풍 및 유의파고, 파장, 파주기의 분포도를 제시하였다.

• Wind and Structures
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• 제30권2호
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• pp.165-180
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• 2020

To determine tornadic wind loads, the wind pressure, forces and moments induced by tornadoes on civil structures have been studied. However, in most previous studies, only the individual building of interest was included in the wind field, which may be suitable to simulate the case where a tornado strikes rural areas. The statistical data has indicated that tornadoes induce more significant fatalities and property loss when they attack densely populated areas. To simulate this case, all buildings in the community of interest should be included in the wind field. However, this has been rarely studied. To bridge this research gap, this study will systematically investigate the influence of a community of buildings on tornadic wind fields by modeling all buildings in the community into the wind field (designated as "the Community case under tornadic winds"). For comparison, the case in which only a single building is included in the tornadic wind field (designated as "the Single-building case under tornadic winds") and the case where a community of buildings are included in the equivalent straight-line wind field (designated as "the Community case under straight-line winds") are also simulated. The results demonstrate that the presence of a number of buildings completely destroys the pattern of regular circular strips in the distribution of tangential velocity and pressure on horizontal planes. Above the roof height, the maximum tangential velocity is lower in the Community case under tornadic winds than that in the Single-building case under tornadic winds because of the higher surface friction in the Community case; below the roof height, greater tangential velocity and pressure are observed in the Community case under tornadic wind fields, and more unfavorable conditions are observed in the Community case under tornadic winds than under the equivalent straight-line winds.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제24권1호
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• pp.29-45
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• 1996

Before (March 26, 1994) or after the occurrence of a downslope windstorm (March 29), the NO, $NO_2$, and $SO_2$ at the ground level of Kangnung city were monitored with high concentrations in the afternoon, due to a large amount of gases emitted from combustion of motor vehicle and heating apparatus, especially near 1600-1800 LST and 2000-2100 LST, but at night, they had low concentrations, resulting from small consumptions of vehicle and heating fuels. When both moderate westerly synoptic-scale winds flow over Mt. Taegwallyang and easterly meso-scale sea breeze during the day, atmospheric pollutants should be trapped by two different wind systems, resulting in higher concentration at Kangnung city in the afternoon. At night, the association of westerly synoptic wind and land breeze can produce relatively strong winds and the dissipation by the winds cause these low concentrations to lower and lower, as nightime goes on. From March 27 through 28, an enforced localized windstorm could be produced along the lee side of the mountain near Kangnung, generating westerly internal gravity waves with hydraulic jump motions. Sea breeze toward inland appartantly confines to the bottom of the eastern side of the mountain, due to the interruption of eastward violent internal gravity waves. As the windstorm moves down toward the ground, an encountering point of two opposite winds approaches Kangnung, and a great amount of NO and $NO_2$ were removed by the strong surface winds. Thus, their maximum concentrations are found to be near 18 and 20 LST, 17 and 21 LST. In the nighttime, the more developed storm should produce very strong surface winds and the NO and $NO_2$ could be easily dissipated into other place. The $SO_2$ concentration had no maximum value, that is, almost constant one all day long, due to its removal by the strong surface winds. Especially, the CO concentrations were slightly lower during the strom period than both before or after the strom, but they were nearly constant without much changes during the during the daytime and nighttime.

• Wind and Structures
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• 제35권1호
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• pp.21-34
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• 2022

Gust factor is an important parameter for the conversion between peak gust wind and mean wind speed used for the structural design and wind-related hazard mitigation. The gust factor of typhoon wind is observed to show a significant dispersion and some differences with large-scale weather systems, e.g., monsoons and extratropical cyclones. In this study, insitu measurement data captured by 13 meteorological towers during a strong typhoon Morakot are collected to investigate the statistical characteristics, height and wind speed dependency of the gust factor. Onshore off-sea and off-land winds are comparatively studied, respectively to characterize the underlying terrain effects on the gust factor. The theoretical method of peak factor based on Gaussian assumption is then introduced to compare the gust factor profiles observed in this study and given in some building codes and standards. The results show that the probability distributions of gust factor for both off-sea winds and off-land winds can be well described using the generalized extreme value (GEV) distribution model. Compared with the off-land winds, the off-sea gust factors are relatively smaller, and the probability distribution is more leptokurtic with longer tails. With the increase of height, especially for off-sea winds, the probability distributions of gust factor are more peaked and right-tailed. The scatters of gust factor decrease with the mean wind speed and height. AS/NZ's suggestions are nearly parallel with the measured gust factor profiles below 80m, while the fitting curve of off-sea data below 120m is more similar to AIJ, ASCE and EU.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 1994년도 학술발표회
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• pp.45-45
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• 1994

• 대한환경공학회지
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• 제36권10호
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• pp.698-703
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• 2014

강어귀의 기하학적 특징과 바람의 방향(upwelling, onshore, downwelling, and offshore winds)에 의한 담수 확산의 변화에 대하여 3차원 해양 순환 모델인 Regional Ocean Modeling System (ROMS)을 이용하여 연구하였다. 총 4개의 임의의 강어귀를 가정하였으며, 담수가 수심이 깊어지는 바다(sloping shelf)에 진입했을 경우가 편평한 바다(flat shelf)에 진입한 경우에 비해 빠른 x, y 운동량(momentum)의 상실과 상대적으로 강한 Coriolis 효과로 인하여 외해로의 담수 확산이 제한되는 것으로 연구되었다. 바람은 수직혼합을 촉진시켜 성층현상을 파괴한다는 기존 연구에 반해 약용승풍(mild upwelling winds)과 외해풍(offshore winds)의 경우(${\mid}{\tau}_{\omega}{\mid}=0.01Pa$) 성층현상을 촉진시키는 것으로 연구되었다. 이와는 반대로 침강풍(downwelling winds)과 연안풍(onshore winds)의 경우 기존 연구와 같이 성층을 파괴하는 것으로 연구되었다. 해저 물길(submarine channel)은 담수확산에 직접적인 영향을 주며 물길의 방향 또는 폭 등과 같은 해저 물길의 기하학적 특징에 의해 담수의 확산 정도가 달라지는 것으로 연구되었다. 또한 해저 물길은 담수 확산을 해저 물길의 상층부로 강하게 제한하는 것으로 연구되었다.