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.

scholarly journals Relationship between Sea Surface Drag Coefficient and Wave State

2021 ◽  
Vol 9 (11) ◽  
pp. 1248
Author(s):  
Jian Shi ◽  
Zhihao Feng ◽  
Yuan Sun ◽  
Xueyan Zhang ◽  
Wenjing Zhang ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Momentum Flux ◽  
Sea Surface ◽  
Sea Spray ◽  
Wave Age ◽  
High Wind ◽  
Surface Drag ◽  
Wave State ◽  
Wind Speeds ◽  
Strong Winds

The sea surface drag coefficient plays an important role in momentum transmission between the atmosphere and the ocean, which is affected by ocean waves. The total air–sea momentum flux consists of effective momentum flux and sea spray momentum flux. Sea spray momentum flux involves sea surface drag, which is largely affected by the ocean wave state. Under strong winds, the sea surface drag coefficient (CD) does not increase linearly with the increasing wind speed, namely, the increase of CD is inhibited by strong winds. In this study, a sea surface drag coefficient is constructed that can be applied to the calculation of the air–sea momentum flux under high wind speed. The sea surface drag coefficient also considers the influence of wave state and sea spray droplets generated by wave breaking. Specially, the wave-dependent sea spray generation function is employed to calculate sea spray momentum flux. This facilitates the analysis not only on the sensitivity of the sea spray momentum flux to wave age, but also on the effect of wave state on the effective CD (CD, eff) under strong winds. Our results indicate that wave age plays an important role in determining CD. When the wave age is >0.4, CD decreases with the wave age. However, when the wave age is ≤0.4, CD increases with the wave age at low and moderate wind speeds but tends to decrease with the wave age at high wind speeds.

scholarly journals Experimental Study of High Wind Sea Surface Drag Coefficient

2015 ◽  
Author(s):  
I.A. Repina ◽  
A.Yu. Artamonov ◽  
M.I. Varentsov ◽  
A.V. Kozyrev ◽  
◽  
...  
Keyword(s):  
Experimental Study ◽  
Drag Coefficient ◽  
Sea Surface ◽  
High Wind ◽  
Surface Drag ◽  
Wind Sea

scholarly journals Experimental Study of High Wind Sea Surface Drag Coefficient

2015 ◽  
Author(s):  
I.A. Repina ◽  
A.Yu. Artamonov ◽  
M.I. Varentsov ◽  
A.V. Kozyrev ◽  
◽  
...  
Keyword(s):  
Experimental Study ◽  
Drag Coefficient ◽  
Sea Surface ◽  
High Wind ◽  
Surface Drag ◽  
Wind Sea

scholarly journals DEVELOPMENT OF AN INVERSE ESTIMATION METHOD OF SEA SURFACE DRAG COEFFICIENT UNDER STRONG WIND CONDITIONS

2011 ◽  
Vol 1 (32) ◽  
pp. 32 ◽  
Author(s):  
Masaki Yokota ◽  
Noriaki Hashimoto ◽  
Koji Kawaguchi ◽  
Hiroyasu Kawai
Keyword(s):  
Drag Coefficient ◽  
A Priori ◽  
Estimation Method ◽  
Sea Surface ◽  
Observation Data ◽  
Strong Wind ◽  
High Wind ◽  
Surface Drag ◽  
Inverse Estimation ◽  
The Given

For the purpose of clarifying the mechanism of energy transfer from high wind to waves, the ADWAM, a wave prediction model incorporating the data assimilation method, was modified to deduce the sea surface drag coefficients as its control variables. Validity of the model was verified through the identical twin experiment in deep sea conditions. Also, the behavior of the deduced parameter was examined through several experiments. As a result, it was confirmed that the drag coefficient deduced by the model is accurate enough when the number of the given observation data is sufficient compared with the number of the unknown parameter. It was also confirmed that the accuracy of the deduced coefficient can be improved by adding an a priori condition even if the number of the observation data is insufficient.

Dependence of sea surface drag coefficient on wind-wave parameters

2011 ◽  
Vol 30 (2) ◽  
pp. 14-24 ◽  
Author(s):  
Jian Shi ◽  
Zhong Zhong ◽  
Ruijie Li ◽  
Yan Li ◽  
Wenyu Sha
Keyword(s):  
Drag Coefficient ◽  
Wind Wave ◽  
Sea Surface ◽  
Surface Drag ◽  
Wave Parameters

scholarly journals Parameterization of Sea Surface Drag Coefficient for All Wind Regimes Using 11 Aircraft Eddy-Covariance Measurement Databases

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1485
Author(s):  
Zhiqiu Gao ◽  
Shaohui Zhou ◽  
Jianbin Zhang ◽  
Zhihua Zeng ◽  
Xueyan Bi
Keyword(s):  
Wind Speed ◽  
Transfer Coefficient ◽  
Drag Coefficient ◽  
Sea Surface ◽  
Turbulent Heat Transfer ◽  
Horizontal Wind ◽  
Turbulent Heat ◽  
Mean Flow ◽  
Surface Drag ◽  
Horizontal Wind Speed

The drag coefficient is essential for calculating the aerodynamic friction between air and sea. In this study, we regress a set of relationships between the drag coefficient and the wind speed for different wind ranges using an observational dataset that consists of 5941 estimates of the mean flow and fluxes from 11 aircraft turbulent measurements over the sea surface. Results show that: (1) the drag coefficient is a power function of wind speed over smooth sea surface when it is no greater than 4.5 ms−1, and the drag coefficient decreases with the increase of wind speed; and (2) for rough sea surface, when the wind speed is greater than 4.5 ms−1 and less than or equal to 10.5 ms−1, the drag coefficient increases linearly with the increase of horizontal wind speed; when the wind speed is greater than 10.5 ms−1 and less than or equal to 33.5 ms−1, the drag coefficient changes parabolically with the increase of wind speed; when the wind speed is greater than 33.5 ms−1, the drag coefficient is constant. Additionally, regressed from drag coefficient, the saturated wind speed threshold is 23 ms−1. Parameterizations of turbulent heat transfer coefficient (Ch) and water vapor transfer coefficient (Ce) are also investigated.

Laboratory investigation of air-sea momentum transfer under severe wind conditions

2020 ◽  
Author(s):  
Maksim Vdovin ◽  
Georgy Baydakov ◽  
Daniil Sergeev ◽  
Yuliya Troitskaya
Keyword(s):  
Wind Speed ◽  
Data Processing ◽  
Drag Coefficient ◽  
Financial Support ◽  
Water Surface ◽  
Wind Wave ◽  
Aerodynamic Resistance ◽  
Sea Surface ◽  
Surface Drag ◽  
Wave Flume

<p>Wind-wave interaction at extreme wind speed is of special interest now in connection with the problem of explanation of the sea surface drag saturation at the wind speed exceeding 30 m/s. Now it is established that at hurricane wind speed the sea surface drag coefficient is significantly reduced in comparison with the parameterization obtained at moderate to strong wind conditions.</p><p>The subject of this work is investigation of aerodynamic resistance of the waved water surface under severe wind conditions (up to U10 ≈ 50 m/s). Laboratory experiments were carried out at the new high-speed wind-wave flume in the Large Thermally Stratified Tank (at the Institute of Applied Physics, Russia) built in 2019. The main difference between the new wind-wave flume and the old one is the absence of a pressure gradient along the main axis of the new flume. Aerodynamic resistance of the water surface was measured by the profile method with Pitot tube. A method for data processing taking into account the self-similarity of the air flow velocity profile in the aerodynamic tube was applied for retrieving wind friction velocity and surface drag coefficients. Simultaneously with the airflow velocity measurements, the wind-wave field parameters in the flume were investigated by system of wire gauges.</p><p>Analysis of the wind velocity profiles and wind-wave spectra showed tendency to decrease for surface drag coefficient for wind speed exceeding 25 m/s simultaneously with the mean square slope and significant wave height.</p><p><span>Acknowledgments</span> <br>This work was carried out with the financial support of the RFBR according to the research project 18-55-50005, 20-05-00322, 18-35-20068, 18-05-00265. Data processing was carried out with the financial support of Russian Science Foundation grant 19-17-00209.</p>

Storm Surge Estimation Along Tokyo Bay Based on a Simple Stochastic Approach

2018 ◽  
Author(s):  
Rikito Hisamatsu ◽  
Sooyoul Kim ◽  
Shigeru Tabeta
Keyword(s):  
Numerical Model ◽  
Storm Surge ◽  
Return Period ◽  
Empirical Formula ◽  
Stochastic Analysis ◽  
Storm Surges ◽  
Stochastic Approach ◽  
Insurance Companies ◽  
Tokyo Bay ◽  
Risk Transfer

In recent years, refinement of stochastic storm surge estimation is essential for risk management in insurance industries because the Japanese government promotes flood risk transfer to insurance companies. Insurance systems may reach peak risk when storm surge damage occurs; however, there are only a few studies on the stochastic analysis of storm surges. This paper presents the stochastic evaluation of storm surges in Tokyo Bay. First, storm surges are assessed using two methods of an empirical formula and a numerical model. Then, the return period of storm surges is stochastically evaluated. It is found that an empirical formula underestimates the surge level in comparison to the numerical model. Based on the results of numerical model, the return period of a storm surge is proposed in Tokyo Bay.

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