• Wind and Structures
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• 제19권4호
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• pp.421-441
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• 2014

With the assistance of typhoon field data at aerial elevation level observed by meteorological satellites and wind velocity and direction records nearby the ground gathered in Guangzhou Weather Station between 1985 and 2001, some key wind field parameters under typhoon climate in Guangzhou region were calibrated based on Monte-Carlo stochastic algorithm and Meng's typhoon numerical model. By using Peak Over Threshold method (POT) and Generalized Pareto Distribution (GPD), Wind field characteristics during typhoons for various return periods in several typical engineering fields were predicted, showing that some distribution rules in relation to gradient height of atmosphere boundary layer, power-law component of wind profile, gust factor and extreme wind velocity at 1-3s time interval are obviously different from corresponding items in Chinese wind load Codes. In order to evaluate the influence of typhoon field parameters on long-span flexible bridges, 1:100 reduced-scale wind field of type B terrain was reillustrated under typhoon and normal conditions utilizing passive turbulence generators in TJ-3 wind tunnel, and wind-induced performance tests of aero-elastic model of long-span Guangzhou Xinguang arch bridge were carried out as well. Furthermore, aerodynamic admittance function about lattice cross section in mid-span arch lib under the condition of higher turbulence intensity of typhoon field was identified via using high-frequency force-measured balance. Based on identified aerodynamic admittance expressions, Wind-induced stochastic vibration of Xinguang arch bridge under typhoon and normal climates was calculated and compared, considering structural geometrical non-linearity, stochastic wind attack angle effects, etc. Thus, the aerodynamic response characteristics under typhoon and normal conditions can be illustrated and checked, which are of satisfactory response results for different oncoming wind velocities with resemblance to those wind tunnel testing data under the two types of climate modes.

• Atmosphere
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• 제30권1호
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• pp.17-30
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• 2020

KMA performed the special observation program to provide information about severe weather and to monitor typhoon PRAPIROON using the ship which called the Gisang 1 from 29 June 2018 to 4 July 2018 (UTC). For this period, upper-air was observed 21 times with 6 hour intervals using rawinsonde in the Gisang 1. We investigated the impact of upper-air observation data from the Gisang 1 on the performance of the operational convective scale model (we called LDAPS). We conducted two experiments that used all observation data including upper-air observation data from the Gisang 1 (OPER) and without it (EXPR). For a typhoon PRAPIROON case, track forecast error of OPER was lower than EXPR until forecast 24 hours. The intensity forecast error of OPER for minimum sea level pressure was lower than EXPR until forecast 12 hours. The intensity forecast error of OPER for maximum wind speed was mostly lower than EXPR until forecast 30 hours. OPER showed good performance for typhoon forecast compared with EXPR at the early lead time. Two precipitation cases occurred in the south of the Korean peninsula due to the impact of Changma on 1 July and typhoon on 3 July. The location of main precipitation band predicted from OPER was closer to observations. As assimilating upper-air data observed in the Gisang 1 to model, it showed positive results in typhoon and precipitation cases.

• Journal of the Korean association of regional geographers
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• 제22권2호
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• pp.450-465
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• 2016

The purpose of this study is to examine the spatial characteristics of relationships between the intensity of extreme climate events driven by typhoons and the magnitude of economic damages at local municipality scales across the Republic of Korea for the recent 15-year period (2000~2014). As results, it is observed that the intensity of extreme temperature events such as heavy rainfall and gusty wind accounts for 50% of the damages magnitude across Korea, while the correlation between the two at the Si-Gun municipality level regionally varies. Positive correlations between the intensity of heavy rainfall events and typhoon damages are observed in the southeastern regions of Taebaek-Sobaek mountain ridges, while such statistically-significant patterns are not detected in the northwestern region. In contrast, statistically-significant positive correlations between the strength of gusty winds and damages are found in most of regions except for some interior regions and northeastern mountainous regions. Classification maps of major extreme climate event types (heavy rainfall-prevailing type, gusty wind-prevailing type, and their combined type) leading to typhoon damages at the Si-Gun municipality scales provided in this study may help local administrations to make the optimized policies for typhoon damage mitigation.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.327-331
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• 2007

23 tropical cyclones of tropical storm(TS) intensity or higher formed in the western North Pacific and the South China Sea in 2006. The total number is less than the 30-year $(1971{\sim}2000)$ average frequency of 26.7, Out of 23, 15 cyclones reached typhoon(TY) intensity, three severe tropical storm(STS) intensity, and five TS intensity. The tropical cyclone season in 2006 began in May with the formation of CHANCHU(0601). While convective activity was slightly inactive around the Philippines from late June to early August. In addition, subtropical high was more enhanced than normal over the south of Japan from May to early August. Consequently, most tropical cyclones formed over the sea east of the Philippines after late June, and many of them moved westwards to China. CHANCHU(0601), BILIS(0604), KAEMI(0605), PRAPIROON(0606) and SAOMI(0608) brought damage to China, the Philippines, and Vietnam. On the other hand, EWINIAR(0603) moved northwards and hit the Republic of Korea, causing damage to the country From late August to early September, convective activity was temporarily inactive over the sea east of the Philippines. However, it turned active again after late September. Subtropical high was weak over the south of Japan after late August. Therefore, most tropical cyclones formed over the sea east of the Philippines and moved northwards. WUKONG(0610) and SHANSHAN(0613) hit Japan to bring damage to the country. On the other hand, XANGSANE(0615) and CIMARON(0619) moved westwards in the South China Sea, causing damage to the Philippines, Thailand, and Vietnam. In addition, IOKE(0612) was the first namded cyclone formed in the central North Pacific and moved westwards across longitude 180 degrees east after HUKO(0224).

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제23권6호
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• pp.458-465
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• 2011

Characteristics of nearshore surge intensity were investigated by analyzing the tide data at 20 tidal stations. Statistical analysis of the surge data show that surge heights at the western coast are far greater than those at southern and eastern coasts, implying that each coast has its own classified characteristics. Surge height data greater than 30 cm were chosen and their intensities were calculated, and then, typhoon-induced surges were separated. The results show that while surge intensity at the western coast is conspicuous in winter due to the monsoon, it is conspicuous in summer due to the typhoon at other coasts. EOF analysis show that the 1st eigenvector at the western coast is prominent, which is considered to be consistent with above mentioned results.

• Atmosphere
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• 제16권2호
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• pp.97-110
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• 2006

This study investigates the response of a typhoon model to the change of the sea surface temperature (SST) throughout the model integration. The SST change is parameterized as a formulae of which the magnitude is given as a function of not only the intensity and the size but the moving speed of tropical cyclone. The formulae is constructed by referring to many previous observational and numerical studies on the SST cooling with the passage of tropical cyclones. Since the parameterized cooling formulae is based on the mathematical expression, the resemblance between the prescribed SST cooling and the observed one during the period of the numerical experiment is not complete nor satisfactory. The agreements between the prescribed and the observed SST even over the swath of the typhoon passage differ from case to case. Numerical experiments are undertaken with and without prescribing the SST cooling. The results with the SST cooling do not show clear evidence in improving the track prediction compared to those of the without-experiments. SST cooling in the model shows its swath along the incomplete simulated track so that the magnitude and the distribution of the sea surface cooling does not resemble completely with the observed one. However, we have observed a little improvement in the intensity prediction in terms of the central pressure of the tropical cyclone in some cases. In case where the model without the SST treatment is not able to yield a correct prediction of the filling of the tropical cyclone especially in the decaying stage, the pulling effect given by the SST cooling alleviates the over-deepening of the model so that the central pressure approaches toward the observed value. However, the opposite case when the SST treatment makes the prediction worse may also be possible. In general when the sea surface temperature is reduced, the amount of the sensible and the latent heat from the ocean surface become also reduced, which results in the weakening of the storms comparing to the constant SST case. It turns out to be the case also in our experiments. The weakening is realized in the central pressure, maximum wind, horizontal temperature gradient, etc.

• Journal of the Korean earth science society
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• 제36권5호
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• pp.460-475
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• 2015

A number of heavy rainfall events on the Korean Peninsula are indirectly influenced by tropical cyclones (TCs) when they are located in southeastern China. In this study, a heavy rainfall case in the middle Korean region is selected to examine the influence of typhoon simulation performance on predictability of remote rainfall over Korea as well as direct rainfall over Taiwan. Four different numerical experiments are conducted using Weather Research and Forecasting (WRF) model, toggling on and off two different improvements on typhoon in the model initial condition (IC), which are TC bogussing initialization and dropwindsonde observation data assimilation (DA). The Geophysical Fluid Dynamics Laboratory TC initialization algorithm is implemented to generate the bogused vortex instead of the initial typhoon, while the airborne observation obtained from dropwindsonde is applied by WRF Three-dimensional variational data assimilation. Results show that use of both TC initialization and DA improves predictability of TC track as well as rainfall over Korea and Taiwan. Without any of IC improvement usage, the intensity of TC is underestimated during the simulation. Using TC initialization alone improves simulation of direct rainfall but not of indirect rainfall, while using DA alone has a negative impact on the TC track forecast. This study confirms that the well-suited TC simulation over southeastern China improves remote rainfall predictability over Korea as well as TC direct rainfall over Taiwan.

• Structural Engineering and Mechanics
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• 제10권6호
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• pp.545-559
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• 2000

A Wind and Structural Health Monitoring System (WASHMS) has been installed in the Tsing Ma suspension Bridge in Hong Kong with one of the objectives being the verification of analytical processes used in wind-resistant design. On 2 August 1997, Typhoon Victor just crossed over the Bridge and the WASHMS timely recorded both wind and structural response. The measurement data are analysed in this paper to obtain the mean wind speed, mean wind direction, mean wind inclination, turbulence intensity, integral scale, gust factor, wind spectrum, and the acceleration response and natural frequency of the Bridge. It is found that some features of wind structure and bridge response are difficult to be considered in the currently used analytical process for predicting buffeting response of long suspension bridges, for the Bridge is surrounded by a complex topography and the wind direction of Typhoon Victor changes during its crossing. It seems to be necessary to improve the prediction model so that a reasonable comparison can be performed between the measurement and prediction for long suspension bridges in typhoon prone regions.

• Current Research on Agriculture and Life Sciences
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• 제15권
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• pp.53-67
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• 1997

The objective of this study is to provide with the hydro-meteological and probabilistic characteristics of the storms of typhoons that have been passed through the Korean peninsula during the last twenty-three years since 1961. The paths and intensities of the typhoons were analyzed. Fifty weather stations were selected and the rainfall data during typhoon periods were collected. Rainfall data were analyzed for the patterns and probabilistic distributions. The results were presented to describe the areal distributions of probabilistic characteristics. The results obtained from this study can be summarized as follows: 1. The most frequent typhoon path that has passed through the Korean peninsula was type E, followed by types CWE, W, WE, and S. The most frequent typhoon intensity was type B, followed by A, super A, and e types, respectively. 2. The third quartile typhoon rainfall patterns appear most frequently followed by the second, first, and last quartiles, respectively, in Seoul, Pusan, Taegu, Kwangju and Taejon. The single typhoon rainfalls with long rainfall durations tended to show delayed type rainfall patterns predominantly compared to the single rainfalls with short rainfall durations. 3. The most frequent probabilistic distribution of typhoon rainfall event is Pearson type-III, followed by Two-parameter lognormal distribution, and Type-I extremal distribution. 4. The most frequent probability distribution model of seashore location was Pearson type-III distribution. The most frequent probability distribution model of inland location was two parameter lognormal distribution.

• Journal of Navigation and Port Research
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• 제34권6호
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• pp.453-458
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• 2010

This paper studies relationship between global warming and trends of typhoon variation by using the meteorological long-term data. The results show that yearly mean typhoon's occurrence numbers decrease and maximum wind speeds strengthen gradually. These results are in accord with most of simulated results. While the normal course of typhoon is increased, the westward course of that is decreased. Typhoon trajectories show that the ratios of normal course 6 : westward course 3 : abnormal course 1 in the last 10 years. Among typhoons which affect to the Korea ones pass through the southern coast of Korea are the most. The numbers of typhoon pass through the western coast of Korea are decreased and those pass through the eastern coast of Korea show increasing trend lately. The notable point in relation to the global warming is that typhoon intensity is strengthened gradually. Watch and counterplan in the viewpoint of prevention to the meteorological disasters are required.