Sooyoul Kim

Local amplification of storm surge by Super Typhoon Haiyan in Leyte Gulf

Typhoon Haiyan, which struck the Philippines in November 2013, was an extremely intense tropical cyclone that had a catastrophic impact. The minimum central pressure of Typhoon Haiyan was 895 hPa, making it the strongest typhoon to make landfall on a major island in the western North Pacific Ocean. The characteristics of Typhoon Haiyan and its related storm surge are estimated by numerical experiments using numerical weather prediction models and a storm surge model. Based on the analysis of best hindcast results, the storm surge level was 5–6 m and local amplification of water surface elevation due to seiche was found to be significant inside Leyte Gulf. The numerical experiments show the coherent structure of the storm surge profile due to the specific bathymetry of Leyte Gulf and the Philippines Trench as a major contributor to the disaster in Tacloban. The numerical results also indicated the sensitivity of storm surge forecast.

A study of a real-time storm surge forecast system using a neural network at the Sanin Coast, Japan

This study investigates the sensitivity of real-time storm surge forecasts to local measured data in an artificial neural network along the Sanin Coast, Japan. The forecast experiments were conducted by combining the various components for the input data; the sea surface level, the sea level pressure, its depression rate, the wind speed, the wind direction and the typhoon position, increasing the numbers of measurement stations and typhoon events. It is found that the increasing numbers of components, stations and events result in the accurate storm surge prediction in the neural network. In addition, it appears that the predicted storm surges are closer to the observation in the neural network trained with the forecast lead times of 1h and 2h than.

NUMERICAL STUDY OF STORM SURGES IN THE SETO INLAND SEA BY MULTI PHYSICS MODEL

This study proposes a multi physics model which consists of atmosphere, tide, surge and wave physics. It was applied to storm surge prediction in the Seto Inland Sea with complex topography and large tidal fluctuation. The storm surges generated by Typhoon Chaba and Songda were hind casted well by the numerical model of SuWAT using the mesoscale weather model output under fluctuating tide condition since the pressure and wind field is well estimated by the weather model. The hind casted water level variation by an empirical typhoon model under high water sea level is underestimated in comparison with the measurements.

The Mechanism of After-Runner Storm Surge Along the North Coast of Vietnam

In this study, the mechanism of abnormal surge along the North coast of Vietnam after the Typhoon Kalmaegy (September/2014) landfalled at Quang Ninh province was analyzed based on the observation data and the results of a coupled model of surge, wave and tide (called SuWAT), by using asymmetric and symmetric wind and pressure fields. For the asymmetric wind and pressure field, the Weather Research and Forecasting (WRF) model is used, while for the symmetric wind and pressure field, a parametric wind and pressure model is used. In the case using wind and pressurefields from the WRF model, the case not consider the effect of tail wind field after the typhoon landfalled is also conducted in order to assess the role of the wind field before and after the typhoon landfall on the surge. The results show that the case use wind and pressure field from the WRF model showed better agreement with observations data. It is due to the WRF model was well simulated the wind and pressure field before and after the typhoon landfall. The strong tail wind is mainly cause the high of surge in the area. This research results will be useful in warning and forecasting storm surges in the area.

THE STUDY ON QUANTITATIVE ASSESSMENT OF STORM SURGE COMPONENTS BY NUMERICAL MODEL

In this study, components of storm surge caused by wind, atmospheric pressure and wave are calculated and analyzed by using integrated numerical models of tides, waves and storm surge (SuWAT - Surge, Wave and Tide). The influence of tide is also considered. In which, tide and storm surge are calculated based on two-dimensional nonlinear shallow water equations considering surge component generated by wave radiation stress that is calculated from the SWAN model, a component model in SuWAT model. The model is applied to calculate storm surge during Xangsane typhoon in Da Nang in September 2006 with a number of different computing cases. The results show that influence of tide is negligible due to small tidal amplitude, surge caused by atmospheric pressure is only significant in offshore areas where storm intensity is still strong. Meanwhile, surge components caused by wind stress and wave radiation stress dominate total water level in coastal areas.

Assessment of Storm Surge along the Coast of Central Vietnam

ABSTRACT Thuy, N.B.; Kim, S.; Chien, D.D.; Dang, V.H.; Cuong, H.D.; Wettre, C., and Hole, L.R., 2017. Assessment of storm surge along the coast of central Vietnam. In the present paper, the interaction of surge, wave, and tide along the coast of central Vietnam is assessed using a coupled model of surge, wave, and tide. A series of storm surge simulations for Typhoons Xangsane (2006), Ketsana (2009), and Nary (2013) are carried out, considering the effects of tides and waves that combines wave-dependent drag and wave-induced radiation stress to find a predominant factor in storm surge generation. The results indicate that the surge–wave interaction is crucial to the storm surge simulation in this area. In particular, the wave-dependent drag improves an accuracy of the storm surge level up to 30%. In addition, the radiation stress contributes up to 15%. However, the tide–surge interaction is negligible because there is less than 2% difference in results with and without the tide. A series of coupled surge and wave simulations for 49 historical typhoons in the period of 1951 to 2014 show that mean peak surge levels along the coast are 2.5 m. The highest peak surge level reached 4.1 m at Cuaviet in the Quangtri Province during Typhoon Harriet (1971).

Estimation of Climate Change Impact on Storm Surges: Application to Korean Peninsula

The present study assesses the climate change impact on local storm surges along the coasts of the Korean Peninsula and Tottori Prefecture, Japan. A series of storm surge simulations are conducted on a physical process-based storm surge model using direct forcing from general circulation model output data in the two periods of 1979–2008 and 2075–2099. It is found that the typhoon intensity is enhanced and its number increases under the future climate condition in the area of the Korean Peninsula (32° to 40° N and 120° to 138° E). In addition, the typhoon approach course moves by 0.523° westward in the future climate. From a series of storm surge simulations, the statistical analysis showed that the climate change influences the storm surge height regionally and locally; it decreases on the west coast of the Korean Peninsula in the future, whereas it increases on the south coast of the Korean Peninsula and on the coast of Tottori Prefecture, Japan.

21. STORM SURGE HINDCAST IN TOSA BAY OF JAPAN USING A COUPLED MODEL OF SURGE, WAVE AND TIDE

The storm surge residual of 2.35m was measured during Typhoon Anita in 1970 in the Tosa bay, Japan. Since the Tosa bay widely open to the Pacific Ocean, surge heights are usually small. The present study examined the reasons why the abnormal storm surge was generated due to Typhoon Anita 1970 by numerical simulations using a coupled model of surge, wave and tide with six levels computational domains of which grid sizes are from 12150m to 50m. The storm surge simulation driven by only wind and pressure fields was not able to compute the measured sea surface levels. However, when wave radiation stress terms were included in the storm surge model the computed sea surface levels showed a good agreement with the measurement data. This study clarified that the effect of wave-induced radiation stress is significant on water level rising of up to 0.5m-1.0m in the Tosa bay.

22. EFFECTS OF WAVE RADIATION STRESS AND VERTICAL MIXING ON STORM SURGE

Since major driving forces of storm surge are pressure depression and wind stresse, a set of depth integrated equations is widely used for storm surge simulations to estimate anomaly sea level rise. However, there are several phenomena should be taken into consideration. This study estimates effects of wave radiation stress, vertical mixing models and boundary conditions at ocean upper layers on storm surge. The three dimensional hydro-static model including turbulence mixing and diffusion are used to predict the sea surface elevation in the storm surge. The numerical results show that the wave radiation stress and the turbulent flux significantly influence on sea levels and currents, respectively.

Storm Surge Simulations Occurred in the Tosa Bay by Using Surge-Wave-Tide Coupled Model

The storm surge residual of 2.35m was recorded during Typhoon Anita (T7010) at Katsurahama in the Tosa Bay. The surge could not be explained by usual meteorological forces. The inclusion of the wave-induced radiation stress was necessary. This study examined the effects of waves and tidal variations for estimating the abnormal storm surge by using a coupled model between strom surges and waves together with the tidal variations, named as the SuWAT (Surge-WAve-Tide coupled model), and clarified those effects on the storm surge.