scholarly journals Assimilation Research of Wind Stress Drag Coefficient Based on the Linear Expression

2021 ◽  
Vol 9 (10) ◽  
pp. 1135
Author(s):  
Junli Xu ◽  
Yuling Nie ◽  
Kai Ma ◽  
Wenqi Shi ◽  
Xianqing Lv
Keyword(s):  
Data Assimilation ◽  
Drag Coefficient ◽  
Storm Surge ◽  
Wind Stress ◽  
Bohai Sea ◽  
Storm Surges ◽  
Drag Coefficients ◽  
Initial Values ◽  
Linear Expression ◽  
Better Than

The wind stress drag coefficient plays an important role in storm surge models. This study reveals the influences of wind stress drag coefficients, which are given in form of formulas and inverted by the data assimilation method, on the storm surge levels in the Bohai Sea, Yellow Sea, and East China Sea during Typhoon 7008. In the process of data assimilation, the drag coefficient is based on the linear expression Cd = (a + b × U10) × 10−3 (generally speaking, a and b are empirical parameters determined by observed data). The results showed that the performance of the data assimilation method was far superior to those of drag coefficient formulas. Additionally, the simulated storm surge levels obviously changed in the neighborhood of typhoon eye. Furthermore, the effect of initial values of a and b in the Cd expression on the storm surge levels was also investigated when employing the data assimilation method. The results indicated that the simulation of storm surge level was the closest to the observation when a and b were simultaneously equal to zero, whereas the simulations had slight differences when the initial values of a and b were separately equal to the drag coefficients from the work of Smith, Wu, and Geernaert et al. Therefore, we should choose appropriate initial values for a and b by using the data assimilation method. As a whole, the data assimilation method is much better than drag coefficient parameterization formulas in the simulation of storm surges.

scholarly journals Adjusting the Wind Stress Drag Coefficient in Storm Surge Forecasting Using an Adjoint Technique

2013 ◽  
Vol 30 (3) ◽  
pp. 590-608 ◽  
Author(s):  
Shiqiu Peng ◽  
Yineng Li ◽  
Lian Xie
Keyword(s):  
Data Assimilation ◽  
Drag Coefficient ◽  
Storm Surge ◽  
Wind Stress ◽  
Weather Prediction ◽  
Ocean Model ◽  
Error Sources ◽  
Empirical Parameter ◽  
Forecasting Errors ◽  
Storm Surge Forecasting

Abstract A three-dimensional ocean model and its adjoint model are used to adjust the drag coefficient in the calculation of wind stress for storm surge forecasting. A number of identical twin experiments (ITEs) with different error sources imposed are designed and performed. The results indicate that when the errors come from the wind speed, the drag coefficient is adjusted to an “optimal value” to compensate for the wind errors, resulting in significant improvements of the specific storm surge forecasting. In practice, the “true” drag coefficient is unknown and the wind field, which is usually calculated by an empirical parameter model or a numerical weather prediction model, may contain large errors. In addition, forecasting errors may also come from imperfect model physics and numerics, such as insufficient resolution and inaccurate physical parameterizations. The results demonstrate that storm surge forecasting errors can be reduced through data assimilation by adjusting the drag coefficient regardless of the error sources. Therefore, although data assimilation may not fix model imperfection, it is effective in improving storm surge forecasting by adjusting the wind stress drag coefficient using the adjoint technique.

scholarly journals Inversion of Wind-Stress Drag Coefficient in Simulating Storm Surges by Means of Regularization Technique

2019 ◽  
Vol 16 (19) ◽  
pp. 3591
Author(s):  
Junli Xu ◽  
Yuhong Zhang ◽  
Xianqing Lv ◽  
Qiang Liu
Keyword(s):  
Drag Coefficient ◽  
Storm Surge ◽  
Wind Stress ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Water Levels ◽  
The Yellow Sea ◽  
Regularization Technique ◽  
The Bohai Sea ◽  
Comparison Results

In this study, water levels observed at tide stations in the Bohai Sea, Yellow Sea, and East China Sea during Typhoons 7203 and 8509 were assimilated into a numerical assimilation storm surge model combined with regularization technique to study the wind-stress drag coefficient. The Tikhonov regularization technique with different regularization parameters was tested during the assimilation. Using the regularization technique, the storm surge elevations were successfully simulated in the whole sea areas during Typhoons 7203 and 8509. The storm surge elevations calculated with the regularization technique and the elevations calculated with independent point method were separately compared with the observed data. Comparison results demonstrated that the former was closer to the observed data. The regularization technique had the best performance when the regularization parameter was 100. The spatial distribution of the inverted drag coefficient, storm surge elevations, and the wind fields during both typhoons were presented. Simulated results indicated that the change of drag coefficient is more significant in the coastal regions of the Bohai Sea and north of the Yellow Sea. Further analysis showed that the rising water elevation in the Bohai Sea is mostly attributed to the influence of onshore winds, and the negative storm surge in the South Yellow Sea is mainly caused by offshore winds.

scholarly journals Storm Surges in the Bohai Sea: The Role of Waves and Tides

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1509
Author(s):  
Yuanyi Li ◽  
Huan Feng ◽  
Guillaume Vigouroux ◽  
Dekui Yuan ◽  
Guangyu Zhang ◽  
...  
Keyword(s):  
Storm Surge ◽  
Bohai Sea ◽  
Storm Surges ◽  
Wave Force ◽  
Laizhou Bay ◽  
Bohai Bay ◽  
Coastal Regions ◽  
The Bohai Sea ◽  
Tidal Phase ◽  
Set Up

A storm surge is a complex phenomenon in which waves, tide and current interact. Even though wind is the predominant force driving the surge, waves and tidal phase are also important factors that influence the mass and momentum transport during the surge. Devastating storm surges often occur in the Bohai Sea, a semi-enclosed shallow sea in North China, due to extreme storms. However, the effects of waves on storm surges in the Bohai Sea have not been quantified and the mechanisms responsible for the higher surges that affect part of the Bohai Sea have not been thoroughly studied. In this study, we set up a storm surge model, considering coupled effects of tides and waves on the surges. Validation against measured data shows that the coupled model is capable of simulating storm surges in the Bohai Sea. The simulation results indicate that the longshore currents, which are induced by the large gradient of radiation stress due to wave deformation, are one of the main contributors to the higher surges occurring in some coastal regions. The gently varying bathymetry is another factor contributing to these surges. With such bathymetry, the wave force direction is nearly uniform, and pushes a large amount of water in that direction. Under these conditions, the water accumulates in some parts of the coast, leading to higher surges in nearby coastal regions such as the south coast of the Bohai Bay and the west and south coasts of the Laizhou Bay. Results analysis also shows that the tidal phase at which the surge occurs influences the wave–current interactions, and these interactions are more evident in shallow waters. Neglecting these interactions can lead to inaccurate predictions of the storm surges due to overestimation or underestimation of wave-induced set-up.

scholarly journals Research of the Influential Factors on the Simulation of Storm Surge in the Bohai Sea

2014 ◽  
Vol 8 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Yumei Ding ◽  
Hao Wei
Keyword(s):  
Drag Coefficient ◽  
Storm Surge ◽  
Bohai Sea ◽  
Three Dimensional ◽  
Ocean Model ◽  
Influential Factors ◽  
Influential Factor ◽  
Data Set ◽  
The Bohai Sea ◽  
Sensitivity Studies

A hindcast of typical extratropical storm surge occurring in the Bohai Sea in Oct. 2003 is performed using a three-dimensional storm surge model system based on Finite-Volume Coastal Ocean Model (FVCOM). The surface winds are obtained from the WRF data set. Some preliminary sensitivity studies of the influential factors affecting the storm surge simulation in the Bohai Sea are conducted with the high revolution numerical model of storm surge. The factors of tide-surge interaction, the wind stress, the water depth, the bottom drag coefficient and the critical depth in the model are studied. After considering the tide-wind interaction and the severe wind, the most important influential factor affecting the storm surge in the Bohai Sea is the bottom drag coefficient. These sensitivity studies indicate that the storm surge simulations depend critically on the parameterizations. Hence additional experimental guidance is required on the bottom drag coefficient. This study is useful for the storm surge simulation in order to select the proper parameter to make possible a good conservation behavior of the storm surge model.

Storm Surges in the Southern Beaufort Sea

1976 ◽  
Vol 33 (10) ◽  
pp. 2362-2376 ◽  
Author(s):  
R. F. Henry ◽  
N. S. Heaps
Keyword(s):  
Storm Surge ◽  
Wind Stress ◽  
Numerical Models ◽  
Storm Surges ◽  
Beaufort Sea ◽  
Ice Cover ◽  
The Other ◽  
Operational Forecasting ◽  
Detailed Simulation

Evidence of storm surge occurrence in the Canadian sector of the southern Beaufort Sea is reviewed and distinctions are drawn between surges occurring in the absence and presence of ice cover. Two numerical models are described, one intended for detailed simulation of past surges, the other a compact, economical model designed for operational forecasting of surges. The associated system used to obtain the required wind-stress input to the numerical models is also discussed.

scholarly journals UNCERTAINTY OF EXTREME STORM SURGE ESTIMATION BY HIGH WIND SEA SURFACE DRAG COEFFICIENT AND FUTURE TYPHOON CHANGE

2011 ◽  
Vol 1 (32) ◽  
pp. 18 ◽  
Author(s):  
Hiroyasu Kawai ◽  
Noriaki Hashimoto ◽  
Masaru Yamashiro ◽  
Tomohiro Yasuda
Keyword(s):  
Drag Coefficient ◽  
Storm Surge ◽  
Return Period ◽  
Extreme Values ◽  
Research Output ◽  
Storm Surges ◽  
Sea Surface ◽  
High Wind ◽  
Surface Drag ◽  
Typhoon Vera

Japan has been constructing long coastal defense since the storm surge disaster with a loss of 5,000 lives by Typhoon Vera in 1959. The defense is designed for the storm water level including the storm surge of the standard typhoon based on Typhoon Vera. Stochastic typhoon model, simulating various typhoon track and intensity with Monte Carlo method, is one of useful tools to estimate the return period. According to recent research output the return period of the storm surge of the standard typhoon is near 100 years or more at three major bays in Japan. But there is uncer-tainty by some of parameters and models in the stochastic simulation. Sea surface drag coefficient under high wind speed and future change in typhoon intensity and track are critical to extreme values of the storm surges.

IMPACT ASSESSMENT ON STORM SURGE RISKS TO CONTAINERS CONSIDERING GLOBAL WARMING

2017 ◽  
Author(s):  
Rikito Hisamatsu ◽  
Rikito Hisamatsu ◽  
Kei Horie ◽  
Kei Horie
Keyword(s):  
Risk Assessment ◽  
Global Warming ◽  
Storm Surge ◽  
Storm Surges ◽  
Assessment Tools ◽  
Inundation Depth ◽  
Risk Assessment Tools ◽  
Risk Maps ◽  
The Impact ◽  
Vulnerability Functions

Container yards tend to be located along waterfronts that are exposed to high risk of storm surges. However, risk assessment tools such as vulnerability functions and risk maps for containers have not been sufficiently developed. In addition, damage due to storm surges is expected to increase owing to global warming. This paper aims to assess storm surge impact due to global warming for containers located at three major bays in Japan. First, we developed vulnerability functions for containers against storm surges using an engineering approach. Second, we simulated storm surges at three major bays using the SuWAT model and taking global warming into account. Finally, we developed storm surge risk maps for containers based on current and future situations using the vulnerability function and simulated inundation depth. As a result, we revealed the impact of global warming on storm surge risks for containers quantitatively.

scholarly journals Modeling Study on the Asymmetry of Positive and Negative Storm Surges along the Southeastern Coast of China

2021 ◽  
Vol 9 (5) ◽  
pp. 458
Author(s):  
Dongdong Chu ◽  
Haibo Niu ◽  
Wenli Qiao ◽  
Xiaohui Jiao ◽  
Xilin Zhang ◽  
...  
Keyword(s):  
Storm Surge ◽  
Pressure Field ◽  
Three Dimensional ◽  
Storm Surges ◽  
Ocean Model ◽  
Central Pressure ◽  
Linear Interaction ◽  
Southeastern Coast ◽  
Zhoushan Archipelago ◽  
Wind Intensity

In this paper, a three-dimensional storm surge model was developed based on the Finite Volume Community Ocean Model (FVCOM) by the hindcasts of four typhoon-induced storm surges (Chan-hom, Mireille, Herb, and Winnie). After model validation, a series of sensitivity experiments were conducted to explore the effects of key parameters in the wind and pressure field (forward speed, radius of maximum wind (RMW), inflow angle, and central pressure), typhoon path, wind intensity, and topography on the storm surge and surge asymmetry between sea level rise (positive surge) and fall (negative surge) along the southeastern coast of China (SCC). The model results show that lower central pressure and larger RMW could lead to stronger surge asymmetry. A larger inflow angle results in a stronger surge asymmetry. In addition, the path of Chan-hom is the most dangerous path type for the Zhoushan Archipelago area, and that of Winnie follows next. The model results also indicate that the non-linear interaction between wind field and pressure field tends to weaken the peak surge elevation. The effect of topography on storm surges indicates that the peak surge elevation and its occurrence time, as well as the surge asymmetry, increase with a decreasing slope along the SCC.

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