Han Soo Lee

Abnormal storm waves in the East Sea (Japan Sea) in April 2012

ABSTRACT Lee, H.S., 2013. Abnormal storm waves in the East Sea (Japan Sea) in April 2012 The winter East Sea, a semi-enclosed sea surrounded by Korea in the west, Japan in the east and south and Russia in the north, normally experiences rough sea conditions due to East Asian monsoon and winter storms. In April 2012, record-breaking abnormally high waves, significant wave heights of 11.21 m and 12.39 m and significant wave periods of 13.6 sec and 14.3 sec at Akita and Yamagata GPS buoy sites, respectively, were observed along the Tohoku coast in the East Sea side of Japan. It was due to a well- and fast-developed low pressure passing through the East Sea. This paper describes how a low pressure could be grown so rapidly to tropical cyclone level in this time and numerical hindcast results for future forecast and engineering purpose. With respect to the meteorological condition, it is found that strong convective motion due to latent heat and water vapor from Tsushima Warm Current together with an accompanied front increases a pressure gradient at tropopause level accelerating the low growth. In the hindcast using an atmosphere-wave modeling system, two different initial and boundary condition data, NCEP FNL and JMA GSM, are used for applicability test. The result with NCEP FNL data shows a better agreement with observations in terms of surface winds. The observed peaks of significant wave height and period by Akita and Yamagata GPS buoy are captured well in both results. It is also found that the vertical resolution of initial and boundary condition data is important in atmospheric modeling; the higher vertical resolution tends to produce a deeper storm with lower central pressure and strong convective motion.

A Modelling Study of Seawater Intrusion in the Liao Dong Bay Coastal Plain, China

To investigate the extent of seawater intrusion in the Liao Dong Bay coastal plain, China, a numerical model for variable-density groundwater flow and miscible salt transport was developed. The SEAWAT code was used to solve the density-dependent groundwater flow and solute transport governing equations. The simulation was conducted for 55 months from October, 2004 to April, 2009. The numerical model was calibrated by the hydraulic heads measured in April, 2009. Using the calibrated model and the same hydrogeological conditions in 2004, the extent of seawater intrusion prediction was conducted for the next 40 years. The results show that the extent of seawater intrusion area will increase in all geologic layers with nearly 6.2 km in the upper Quaternary aquifer and 4.3 km in lower Quaternary aquifer for 40 years. In the Minhuazhen group aquifer, the maximum speed of seawater intrusion is 62.2 m/yr. Therefore, some protection of the freshwater aquifer from seawater intrusion in the Liao Dong Bay coastal plain is imperative.

Impacts of tides on tsunami propagation due to potential Nankai Trough earthquakes in the Seto Inland Sea, Japan†

The impacts of tides on extreme tsunami propagation due to potential Nankai Trough earthquakes in the Seto Inland Sea (SIS), Japan, are investigated through numerical experiments. Tsunami experiments are conducted based on five scenarios that consider tides at four different phases, such as flood, high, ebb, and low tides. The probes that were selected arbitrarily in the Bungo and Kii Channels show less significant effects of tides on tsunami heights and the arrival times of the first waves than those that experience large tidal ranges in inner basins and bays of the SIS. For instance, the maximum tsunami height and the arrival time at Toyomaesi differ by more than 0.5 m and nearly 1 h, respectively, depending on the tidal phase. The uncertainties defined in terms of calculated maximum tsunami heights due to tides illustrate that the calculated maximum tsunami heights in the inner SIS with standing tides have much larger uncertainties than those of two channels with propagating tides. Particularly in Harima Nada, the uncertainties due to the impacts of tides are greater than 50% of the tsunami heights without tidal interaction. The results recommend simulate tsunamis together with tides in shallow water environments to reduce the uncertainties involved with tsunami modeling and predictions for tsunami hazards preparedness.

Wintertime Extreme Storm Waves in the East Sea: Estimation of Extreme Storm Waves and Wave-Structure Interaction Study in the Fushiki Port, Toyama Bay

2008년 2월 일본 홋카이도 서해상의 발달된 저기압에 의해 생성된 폭풍파랑이 동해상 남/남서쪽으로 전파되어 한국과 일본의 동해 해안을 따라 상당한 인명 및 재산 피해를 입혔다. 본 연구는 두 파트로 구성되어 있다. 첫번째 파트에서는 연안역을 따라 상당한 피해를 입은 일본 토야마만에서의 극한 폭풍파랑을 추산하였다. 추산방법으로는 풍파의 성장발달에 중요한 요소인 바람의 강도와 계속 시간의 극한조건을 산정 후, 극한조건을 적용한 동계 온대저기압 상황을 비정역학 기상모델과 스펙트럼 파랑모델을 이용한 수치 실험을 통해 추산하였다. 추산된 토야마만 후시키 토야마에서의 극한 폭풍파랑의 유의파고 및 주기는 각각 6.78 m와 18.28 sec이다. 두 번째 파트에서는 2008년 2월 폭풍파랑으로 인해 북방파제 및 항구에 상당한 피해를 입은 토야마만 후시키항에서의 파랑-구조물 상호작용에 관한 수치실험을 수행하였다. 수치실험은 적합격자세분화 및 wet-dry법이 적용된 비선형천수방정식 모델을 이용하였다. 첫 파트에서 추산된 폭풍파랑 특성은 파랑-구조물 상호작용 수치실험에서 입사파 조건으로 사용되었다. 수치실험 결과, 후시키항의 북방파제가 폭풍파랑에 의해 파손 시, 배후의 만요우부두는 월파 및 월류에 안전하지 못 함이 파악되었다. 또한, 추산 폭풍파랑 상황 하에서 만요우부두의 현 호안시설로는 측면 호안벽으로부터의 월류에 대응하지 못 함이 파악되었다. 두 번째 수치실험결과로부터, wet-dry법이 적용된 적합격자세분화에 의해 세분화된 격자는, 계산부하를 효율적으로 유지하는 동시에, 해안선의 표현 및 해안구조물의 표현에 뛰어남을 확인하였다.

Scheme choice for optimal allocation of water resources based on fuzzy language evaluation and the generalized induced ordered weighted averaging operator

The choice of scheme for the optimal allocation of water resource (OAW R) is a fuzzy multiple-attribution decision that is determined using information from many figures and fuzzy language regarding several evaluated factors, such as investment, daily water supplying, fee of contaminated water disposal, water conservation, and the development of economy.In this paper, the evaluation system employed to choose an OAWR scheme is established based on the evaluation of fuzzy language and the generalized induced ordered weighted averaging (GIOWA) operator. Considering economic aspects and a sustainable water supply, the five following constituents are chosen: 1) Investment (Yuan), 2) Daily water supply (ton/day), 3) Fee of contaminated water disposal (Yuan), 4) Water conservation (fuzzy language), and 5) Development of economy (fuzzy language). The analytic hierarchy process (AHP) method is used to determine the weighting vector.A case study on the choice of OAWR in the northern area of Shenyang city, China was conducted by a multiple-attribution decision based on the GIOWA operator. The results shows that the system employed was able to choose the best scheme of OAWR in which fuzzy and multiple-attribution decision-making should be performed.

Estimation and Projection of Non-Linear Relative Sea-Level Rise in the Seto Inland Sea, Japan

ABSTRACT Future sea-level rise (SLR) in and around the Seto Inland Sea (SIS), Japan, is estimated in 2050 and 2100 using ensemble empirical mode decomposition (EEMD) and long-term sea-level records. Ensemble empirical mode decomposition, an adaptive data analysis method, can separate sea-level records into intrinsic mode functions (IMFs) from high to low frequencies and a residual. The residual is considered a non-linear trend in the sea-level records. The mean SLR trend at Tokuyama in the SIS from EEMD is 3.00 mm y−1 from 1993 to 2010, which is slightly lower than the recent altimetry-based global rate of 3.3 ± 0.4 mm y−1 during the same period. Uncertainty in SLR is estimated by considering interdecadal variations in the sea levels. The resulting SLR in 2050 and 2100 for Tokuyama is 0.19 ± 0.06 m and 0.56 ± 0.18 m, respectively. The stations along the coast of the Pacific Ocean display a greater and more rapid SLR in 2100 compared with other stations in the SIS. The SLR is caused not only by mass and volume changes in the sea water but also by other factors, such as local subsidence, tectonic motion, and river discharge. The non-linear trend of SLR, which is the residual from EEMD, is interpreted as the sum of the local factors that contribute to the sea-level budget.

Urban Climate Challenges in Hanoi: Urban Heat Islands and Global Warming

Urban climate of rapidly growing cities such as Hanoi will alter not only owing to land use changes but also global warming effect. This chapter investigates the contributions of land use changes and global warming to the future increases in urban temperature in Hanoi for 2030 through a numerical simulation using the Weather Research and Forecasting (WRF). The future climate data utilized the fifth phase of the Coupled Model Intercomparison Project (CMIP5) projected by the Model for Interdisciplinary Research on Climate Version 5 (MIROC5) through a direct dynamical downscaling method. In the 2030s, the average air temperature increase in the existing urban areas was projected to be up to 2.1 °C, of which up to 1.5 and 0.6 °C are attributable to global warming and land use changes, respectively. The future increase in urban temperature will likely exceed the cooling effects of any urban heat island (UHI) mitigation measures.

Climate Vulnerability in Tropical Asia

The tropical zone encompasses some of the wettest areas on Earth, as well as some of the world’s driest deserts. This zone also includes some of the countries that are the most vulnerable to natural disasters, due to population pressures that drive settlement in flood- or drought-prone areas. Some of the less-developed countries also lack the resources to build structures resilient to climatic extremes. The limitations of physical and human infrastructure also contribute to the limited capacity to warn of or respond to major disasters, although this is an area where large improvements have been made in many countries in recent decades.

Typhoon Morakot Induced Waves and Surges with an Integrally Coupled Tide-Surge-Wave Finite Element Model

ABSTRACT Kim, K.O.; Yuk, J.-H.; Lee, H.S., and Choi, B.H., 2016. Typhoon Morakot induced wave and surges with an integrally coupled tide-surge-wave finite element model. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1122 - 1226. Coconut Creek (Florida), ISSN 0749-0208. A coupled system of unstructured-mesh SWAN and ADCIRC, running on the same unstructured mesh, has been applied to simulate storm surges and waves during typhoon Morakot in August 2009. Emphasis is placed on the effect of wave-tidal current interaction on storm surges and wind waves. Two advantages of this system are that the physics of wave-circulation interactions can be satisfactorily resolved, and a large domain covering a deep ocean and shallow shelf can be dealt with seamlessly, requiring no mesh nesting. Wave refraction and directional spreading induced a wave-current effect, which was confirmed by the cross correlation between the observed significant wave periods and the wave-current angle. The results from the application of the system show that waves resulting from a typhoon can be reasonably simulated in a coastal area. The effect of coupling wave heights and wave periods is found to be approximately 5% and 10%, respectively. Spectral characteristics such as directional spreading and refraction support the influence of tidal current effects on wind waves. This coupled system is a good starting point for operational wave-tide-surge forecasting and can be easily extended to regional sites of interest without a significant increase in the computational burden. The system currently uses a set of depth-integrated equations that simplifies the vertical structure of the current, radiation stress, surface stress and bottom boundary layer.

Numerical study on seawater intrusion into groundwater in Liaodong Bay coastal plain, China

To simulate the and predict seawater intrusion into groundwater in Liao dong Bay coastal plain, China, a numerical model of variable-density groundwater flow and miscible salt transport is developed based on the SEAWAT code. The simulation was conducted for 55 months from October 2004 to April 2009. After calibration of the model, assuming all the hydrogeological conditions remain same as those in October 2009, the extent of seawater intrusion simulation was conducted for the next 40 years. The results show that seawater intrusion area will increase in all layers and seawater intrusion into Quaternary layer will be significantly faster than that into Minhuazhen group layer. It has come to the conclusion that protection of seawater intrusion contamination from the freshwater aquifers of Minhuazhen group layer is significantly necessary.