• Ocean and Polar Research
• /
• v.46 no.1
• /
• pp.1-15
• /
• 2024

This study examines the influence of Hallasan Mountain (Hallasan) on the track and intensity of two Typhoons, Soulik in 2018 and Chaba in 2016, which passed to the left and right of Hallasan, respectively, using a coupled ocean-atmosphere model. We designed three experiments: one with Hallasan's actual altitude, another with the mountain removed, and a third where Hallasan's altitude was doubled. Results showed that Hallasan had a negligible impact on the tracks of both typhoons. Regarding intensity, however, the central pressure of both typhoons increased (indicating weakening) by up to 2 hPa due to Hallasan; the maximum wind speeds initially increased (Soulik by 1 m/s, Chaba by 3 m/s) and then decreased (Soulik by 1 m/s, Chaba by 5 m/s). These results show that Hallasan does not significantly weaken the intensity of typhoons approaching the Korean Peninsula, but considering the average intensity change (-3.45 hPa) of past typhoons that passed to the left of Jeju Island in terms of central pressure, Hallasan makes a noteworthy contribution. Additionally, this study reveals that changes in typhoon winds due to the wind convergence caused by Hallasan's topography can alter ocean vertical mixing and sea surface cooling, further impacting typhoon intensity. This finding underscores the importance of using a coupled ocean-atmosphere model when studying the impact of topography on typhoons.

• Atmosphere
• /
• v.16 no.1
• /
• pp.19-31
• /
• 2006

The purpose of this study is to develop the statistical model to predict sea level pressure of typhoon period in south coast of the Korean Peninsula. Seven typhoons, which struck south coast of the Korean Peninsula, are selected for this study, and the data for analysis include the central pressure and location of typhoon, and sea level pressure and location of 19 observing site. Models employed in this study are the first order regression, the second order regression and the neural network. The dependent variable of each model is a 3-hr interval sea level pressure at each station. The cause variables are the central pressure of typhoon, distance between typhoon center and observing site, and sea level pressure of 3 hrs before, whereas the indicative variable reveals whether it is before or after typhoon passing. The data are classified into two groups - one is the full data obtained during typhoon period and the other is the data that sea level pressure is less than 1000 hPa. The stepwise selection method is used in the regression model while the node number is selected in the neural network by the Schwarz's Bayesian Criterion. The performance of each model is compared in terms of the root-mean square error. It turns out that the neural network shows better performance than other models, and the case using the full data produces similar or better results than the case using the other data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.1
• /
• pp.135-143
• /
• 2014

This study classified abnormal sea surface temperature changes of the central pacific region according to three evolution patterns. Focusing on typhoons that affect the Korean Peninsula, the research analyzed typhoon's occurrence spot and track, change in the central pressure characteristics, and the characteristics of change in typhoon precipitation and the number of occurrences of heavy rainfall in the Nakdong River Basin. As a result of analysis, in case of prolonged-decaying years and symmetric-decaying years, typhoon-related summer rainfall and heavy rainy days appeared to be higher than long-term average. But in case of abrupt-decaying years, the pattern of general decrease appeared. This is because typhoon's occurrence spot is located comparatively near the Korean peninsula, typhoon's central pressure is high, and typhoon's route generally moves to Japan. As the outcome, this study is expected to reduce flood damage through analyzing the characteristics of typhoon's activity according to CP El Ni$\tilde{n}$o evolution patterns and the characteristics of local typhoon rainfall. In addition, it is expected to provide useful information for establishing adaptation and mitigation to climate change.

• Atmosphere
• /
• v.16 no.2
• /
• pp.97-110
• /
• 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 Navigation and Port Research
• /
• v.37 no.6
• /
• pp.611-616
• /
• 2013

This paper studies relationship between typhoon and El Ni$\tilde{n}$o La Ni$\tilde{n}$a events by using 25 years meteorological data of KMA and JMA. The results are listed below. Annual mean number of typhoon's occurrence in El Ni$\tilde{n}$o event year is 23.9, and that in La Ni$\tilde{n}$a event year is 24.9. The number of typhoon's occurrence decreases in El Ni$\tilde{n}$o event year. Mean central minimum pressure and mean maximum wind speed in El Ni$\tilde{n}$o event year are 959.3hPa and 35.8m/s, and those in La Ni$\tilde{n}$a event year are 965.5hPa and 33.7m/s respectively. Intension of typhoon is stronger in El Ni$\tilde{n}$o event year than La Ni$\tilde{n}$a event year. To be more specific mean central minimum pressure is lower 6.2hPa and mean maximum wind speed is stronger 2.1m/s. This result is closely connected with sea area of typhoon's occurrence. Typhoons in El Ni$\tilde{n}$o event year are more likely to occur in east of 150E and south of 10N, but those in La Ni$\tilde{n}$a event year are more likely to occur in 120-150E and north of 20N. Typhoons which occur in east of 150E and south of 10N can be stronger because the typhoons move in broad sea area of high sea surface temperature in western North Pacific.

• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.607-617
• /
• 2019

Global warming and climate change are increasing the intensity of typhoons and hurricanes and thus increasing the risk effects of typhoon and hurricane hazards on nuclear power plants (NPPs). To reflect these changes, a new NPP should be designed to endure design-basis hurricane wind speeds corresponding to an exceedance frequency of $10^{-7}/yr$. However, the short typhoon and hurricane observation records and uncertainties included in the inputs for an estimation cause significant uncertainty in the estimated wind speeds for return periods of longer than 100,000 years. A logic-tree framework is introduced to handle the epistemic uncertainty when estimating wind speeds. Three key parameters of a typhoon wind field model, i.e., the central pressure difference, pressure profile parameter, and radius to maximum wind, are used for constructing logic tree branches. The wind speeds of the simulated typhoons and the probable maximum wind speeds are estimated using Monte Carlo simulations, and wind hazard curves are derived as a function of the annual exceedance probability or return period. A logic tree decreases the epistemic uncertainty included in the wind intensity models and provides reasonably acceptable wind speeds.

• Journal of Navigation and Port Research
• /
• v.29 no.2
• /
• pp.151-157
• /
• 2005

During the period of every summer to early autumn seasons, ships have been wrecked or grounded from effect of a typhoon in the water areas around Korean Peninsula Typhoon Rusa killed more than 100 people in September 2002. Super Typhoon Maemi passed southeast of South Korea in September 12-13, 2003, with a strong gale blowing at a record 60 m/s and caused much ship groundings, collisions and sinkings over 3000 in dockyards, harbors and places of refuge. These are things that could have been prevented had there merely been prior warning. This study outlines the occurrence characteristics of maritime accidents caused by a typhoon in South Korea for the period from 1962 to 2002. The distribution of the accident records is also compared with the trajectories, winds, central pressures of typhoons, passed during the 1990-2003. It is shown that attack frequency of typhoon and number of marine accidents is the highest in August and the marine accidents due to typhoon have a close relation to the distribution of accumulated wind and pressure fields.

• Journal of Navigation and Port Research
• /
• v.33 no.10
• /
• pp.679-683
• /
• 2009

Typhoon numbers and intensity according to the sea areas of occurrence(sea area of A : Caroline Marshall Islands and vicinity, sea area of B : north of $20^{\circ}N$, sea area of C : greater coasting area of Philippines, sea area of D : South China Sea) were analyzed for 22years from 1986 to 2007 using the meteorological administration's data. Yearly mean typhoon numbers are 26.3 and are showed decreasing trend in the sea areas of A, B, C and D. The decreasing trend is especially notable in the sea area of A and is slight in the sea area of D. Yearly mean typhoon number is most in the sea area of A(13.8, about 53％ of all), the next orders are the sea area C(5.6, about 21％), sea area of B(3.8, about 14％) and sea area of D(3.1, about 12％). Typhoon intensity is strongest in the sea area of A(mean central minimum pressure : 951hPa), the next orders are the sea area C(970hPa), sea area of B(975hPa) and sea area of D(983hPa). The time series of yearly mean central minimum pressures for whole sea area is showed slightly decreasing trend, it means that typhoon intensity is strengthened gradually. Results of this ste seare in accord with simulated results on typhoon vntrations in the global warming.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.5
• /
• pp.45-51
• /
• 2008

Due to recent increases of typhoon damages primarily owing to heavy rainfall and stron wind, estimation and analysis of a typhoon's influence has become more important. In this perspective, the statistical models to estimate the rainfall rate during a typhoon were presented in this paper. Central pressure of the typhoon is modeled to be the primary parameter affecting typhoon rainfall rate while relative angle and distance between the center of typhoon and the specific location for observation are secondary variables. Comparisons between the estimated rainfall rate of these models and the observed value in the duration of Typhoon NARI(2007) were analyzed to confirm the availability of these models. The result shows that the present statistical models can estimate typhoon-induced rainfall around Korean Peninsular to some extent.

• Korean Journal of Remote Sensing
• /
• v.11 no.2
• /
• pp.17-27
• /
• 1995

One of the world widely used methods in determining the intensity of a typhoon is Dvorak's technique. By applying the Dvorak's method to the typhoons which affected our country in various degress and extents without regard to their individual severity, we estimated their intensity for six different cases of typhoons. We have derived a regression equation of estimating the central pressures and maximum wind speeds for the six selected typhoons. Their intensity was estimated from the Dvork's method using GMS satellite image data. The derived equation has tested to typhoon ORCHID and the computed values have been compared with the direct observations in its central pressure and maximum wind speed. The computed values in the Dvork's method are smaller in their magnitudes than the observed corresponding values. But their relative magnitudes do not change so much at each different time step. But our results are significantly different from those of NOAA and JMA. The cause of differences are not investigated in depth in this analysis.