• Title, Summary, Keyword: Windstorm

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Evolutionary Nonlinear Compensation and Support Vector Machine Based Prediction of Windstorm Advisory (진화적 비선형 보정 및 SVM 분류에 의한 강풍 특보 예측 기법)

  • Seo, Kisung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.12
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    • pp.1799-1803
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    • 2017
  • This paper introduces the prediction methods of windstorm advisory using GP nonlinear compensation and SVM. The existing special report prediction is not specialized for strong wind, such as windstorm, because it is based on the wide range of predicted values for wind speed from low to high. In order to improve the performance of strong wind reporting prediction, a method that can efficiently classify boundaries of strong wind is necessary. First, evolutionary nonlinear regression based compensation technique is applied to obtain more accurate values of prediction for wind speed using UM data. Based on the prediction wind speed, the windstorm advisory is determined. Second, SVM method is applied to classify directly using the data of UM predictors and windstorm advisory. Above two methods are compared to evaluate of the performances for the windstorm data in Jeju Island in South Korea. The data of 2007-2009, 2011 year is used for training, and 2012 year is used for test.

Study on Mechanisms and Orographic Effect for the Springtime Downslope Windstorm over the Yeongdong Region (봄철 영동 지역 국지 하강풍 메커니즘과 지형 효과에 대한 연구)

  • Kim, Jung-Hoon;Chung, Il-Ung
    • Atmosphere
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    • v.16 no.2
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    • pp.67-83
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    • 2006
  • The statistical analysis for the springtime windstorm in Korea shows that Yeongdong region has the highest occurrence frequency during recent 10 years. The objective of this study is to find possible mechanisms for the downslope windstorm formation in the Yeongdong region by using a mesoscale numerical model, WRF. Dynamical process, wave breaking (hereafter WB), is qualitatively investigated as the candidate mechanism for a windstorm event occurred in 5 April, 2005. WB is developed in upper troposphere downstream, since stable air is lifted by the Taebaek mountain. This process can cause and maintain the severe downslope windstorm by drawing the upper flow down to the surface. And the intensified downslope wind leads the hydraulic jump (hereafter HJ) in downstream region. Froude numbers at Chuncheon (upslope side), Seorak Mountain (crest), Yangyang (lee side), and the East Sea (distant downstream position) are estimated by about 0.4, 1.0, 1.6, and 0.6, respectively. This result implies that the accelerated and supercritical (Fr>1) flow adjusts to the ambient subcritical (Fr<1) conditions in the turbulent HJ. In addition, we find the formation of upstream inversion near top level of the mountain cause the intensification of HJ. Experiments to examine the orographic effect on the mechanisms suggest that the magnitudes of WB and HJ are larger in the experiment of higher topography, but there is no significant difference of windstorm magnitude among the experiments. Another important result from these sensitivity experiments is that the intensity of downslope windstorm strongly depends on the magnitude of upper (2~4 km) wind in upstream side.

Numerical simulation of turbulent flow around a building complex for development of risk assessment technique for windstorm hazards (강풍피해 위험성 평가를 위한 건물군 주위 유동해석)

  • Choi, Choon-Bum;Yang, Kyung-Soo;Lee, Sung-Su;Ham, Hee-Jung
    • Proceedings of the KSME Conference
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    • pp.2737-2742
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    • 2007
  • Strong wind flow around a building complex was numerically studied by LES. The original motivation of this work stemmed from the efforts to develop a risk assessment technique for windstorm hazards. Lagrangian-averaged scale-invariant dynamic subgrid-scale model was used for turbulence modeling, and a log-law-based wall model was employed on all the solid surfaces including the ground and the surface of buildings to replace the no-slip condition. The shape of buildings was implemented on the Cartesian grid system by an immersed boundary method. Key flow quantities for the risk assessment such as mean and RMS values of pressure on the surface of the selected buildings are presented. In addition, characteristics of the velocity field at some selected locations vital to safety of human beings is also reported.

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Review of downslope windstorms in Japan

  • Kusaka, Hiroyuki;Fudeyasu, Hironori
    • Wind and Structures
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    • v.24 no.6
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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.

A Numerical Sensitivity Experiment of the Downslope Windstorm over the Yeongdong Region in Relation to the Inversion layer of Temperature (역전층이 영동 지역의 활강풍에 미치는 영향에 관한 민감도 수치실험 연구)

  • Lee, Jae Gyoo;In, So-Ra
    • Atmosphere
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    • v.19 no.4
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    • pp.331-344
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    • 2009
  • A sensitivity study has been performed using ARPS (Advanced Regional Prediction System) version 5.2.10 in a downslope windstorm case of 12-13 February 2006. The purpose of this study was to find out the role of the inversion layer of temperature mainly in relation to the strength of the downslope winds over the Yeongdong region located downstream of the Taebaek mountains. Under the conditions of N (Brunt-$V{\ddot{a}}is{\ddot{a}}la$ frequency)=0.008 and N=0.016, the effects of the presence of the inversion layer, its variation of height of the layer, and the depth of the layer were identified. The sensitivity experiments suggested that the inversion layer effected the downstream wind speed of the mountains under both conditions of N=0.008 and N=0.016, and notably when the inversion layer was located near the mountain crest the downstream wind speed of the mountains was strong (~ $27ms^{-1}$) only under the condition of N=0.016. In addition, when the atmosphere was rather stable (N=0.016) and the depth of the layer was relatively thin (765 m) the downstream wind speed of the mountains was the strongest (~ $30ms^{-1}$) among the sensitivity experiments.

Diurnal Variation of Atomospheric Pollutant Concentrations Affected by Development of Windstorms along the Lee Side of Coastal Mountain Area

  • Choi, Hyo
    • International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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    • v.24 no.1
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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.

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Study on the Synoptic Meteorological Characteristics of Windstorms Occurring on the Korean Peninsula

  • Park, Jong-Kil;Jung, Woo-Sik;Kim, Eun-Byul;Lee, Bo-Ram
    • Journal of Environmental Science International
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    • v.23 no.10
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    • pp.1673-1691
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    • 2014
  • Although most natural disaster related studies conducted in Korea recently have been related to typhoons or severe rainstorms, the occurrence frequency of disasters due to windstorms or rainstorms is also high. To reduce the strong wind damage caused by strong windstorms due to climate change, basic studies of strong winds are necessary. Therefore, in this study, the types and representative cases of windstorms that were observed to have been higher than 14 m/s, which is the criterion for strong-wind warnings from the Korea Meteorological Administration, were selected from among those windstorm cases that occurred on the Korean Peninsula for 10 years to conduct a statistical analysis of them and determine their synoptic meteorological characteristics. The cases of windstorms occurring on the Korean Peninsula were divided into six weather patterns according to the locations of the anticyclones/cyclones. Among these types, the SH type, which occurs when Siberian Highs expand into the Korean Peninsula, showed the highest occurrence frequency, accounting for at least the majority of the entire occurrence frequency of windstorms together with that of the EC type, which occurs when cyclones develop on the East Sea, and there was no clear yearly trend of the occurrence frequencies of windstorms. The monthly occurrence frequencies of windstorms were formed mainly by typhoons in the summer and the Siberian Highs in the winter, and the months with the highest windstorm occurrence frequencies were December and January, in which mainly the SH and EC type windstorms occurred. March showed the next highest occurrence frequency with10 times, and SH windstorms occurred the most frequently in March, followed by the CC, SC, and EC types of windstorms, in order of precedence. Therefore, attention to these types of windstorms is required. Countermeasures against storm and flood damage in Korea targeting the summer should be re-reviewed together with pre-disaster prevention plans, because cases of storm and flood damage due to windstorms occur more frequently than those due to typhoons, and they occur throughout the year.

Characteristics of Meteorological Variables in the Leeward Side associated with the Downslope Windstorm over the Yeongdong Region (영동지역 지형성 강풍과 관련된 풍하측 기상요소의 특징)

  • Cho, Young-Jun;Kwon, Tae-Yong;Choi, Byoung-Cheol
    • Journal of the Korean earth science society
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    • v.36 no.4
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    • pp.315-329
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    • 2015
  • We investigated the characteristics of meteorological conditions related to the strong downslope wind over the leeward side of the Taebaek Mountains during the period 2005~2010. The days showing the strong wind exceeding $14ms^{-1}$ in Gangwon province were selected as study cases. A total of 15 days of strong wind were observed at Sokcho, Gangneung, Donghae, and Taebaek located over the Yeongdong region. Seven cases related to tropical cyclone (3 cases) and heavy snowfall (2 cases) and heavy rainfall (2 cases) over the Yeongdong region were excluded. To investigate the characteristics of the remaining 8 cases, we used synoptic weather chart, Sokcho radiosonde, Gangneung wind profiler and numerical model. The cases showed no precipitation (or ${\leq}1mm\;day^{-1}$). From the surface and upper level weather chart, we found the pressure distribution of southern high and northern low pattern over the Korean peninsula and warm ridge over the Yeongdong region. Inversion layer (or stable layer) and warm ridge with strong wind were located in about 1~3 km (925~700 hPa) over mountains. The Regional Data Assimilation and Prediction System (RDAPS) indicated that warm core and temperature ridge with horizontal temperature gradient were $0.10{\sim}0.23^{\circ}C\;km^{-1}$ which were located on 850 hPa pressure level above mountaintop. These results were summarized as a forecasting guidance of downslope windstorm in the Yeongdong region.

Predicting ground-based damage states from windstorms using remote-sensing imagery

  • Brown, Tanya M.;Liang, Daan;Womble, J. Arn
    • Wind and Structures
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    • v.15 no.5
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    • pp.369-383
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    • 2012
  • Researchers have recently begun using high spatial resolution remote-sensing data, which are automatically captured and georeferenced, to assess damage following natural and man-made disasters, in addition to, or instead of employing the older methods of walking house-to-house for surveys, or photographing individual buildings from an airplane. This research establishes quantitative relationships between the damage states observed at ground-level, and those observed from space using high spatial resolution remote-sensing data, for windstorms, for individual site-built one- or two-family residences (FR12). "Degrees of Damage" (DOD) from the Enhanced Fujita (EF) Scale were determined for ground-based damage states; damage states were also assigned for remote-sensing imagery, using a modified version of Womble's Remote-Sensing (RS) Damage Scale. The preliminary developed model can be used to predict the ground-level damage state using remote-sensing imagery, which could significantly lessen the time and expense required to assess the damage following a windstorm.

Peak pressures on low rise buildings: CFD with LES versus full scale and wind tunnel measurements

  • Aly, Aly Mousaad;Gol-Zaroudi, Hamzeh
    • Wind and Structures
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    • v.30 no.1
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    • pp.99-117
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    • 2020
  • This paper focuses on the processes of wind flow in atmospheric boundary layer, to produce realistic full scale pressures for design of low-rise buildings. CFD with LES turbulence closure is implemented on a scale 1:1 prototype building. A proximity study was executed computationally in CFD with LES that suggests new recommendations on the computational domain size, in front of a building model, apart from common RANS-based guidelines (e.g., COST and AIJ). Our findings suggest a location of the test building, different from existing guidelines, and the inflow boundary proximity influences pressure correlation and reproduction of peak loads. The CFD LES results are compared to corresponding pressures from open jet, full scale, wind tunnel, and the ASCE 7-10 standard for roof Component & Cladding design. The CFD LES shows its adequacy to produce peak pressures/loads on buildings, in agreement with field pressures, due to its capabilities of reproducing the spectral contents of the inflow at 1:1 scale.