scholarly journals Drag coefficient reduction at very high wind speeds

2006 ◽  
Vol 111 (C3) ◽  
Author(s):  
John A. T. Bye ◽  
Alastair D. Jenkins
Keyword(s):  
Drag Coefficient ◽  
High Wind ◽  
Wind Speeds ◽  
Very High ◽  
Coefficient Reduction

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 Impact of the Reduced Drag Coefficient on Ocean Wave Modeling under Hurricane Conditions

2008 ◽  
Vol 136 (3) ◽  
pp. 1217-1223 ◽  
Author(s):  
Il-Ju Moon ◽  
Isaac Ginis ◽  
Tetsu Hara
Keyword(s):  
Drag Coefficient ◽  
Hurricane Katrina ◽  
Wind Wave ◽  
Wave Model ◽  
High Wind ◽  
Model Surface ◽  
Wind Speeds ◽  
Tank Experiment ◽  
Wave Heights ◽  
Significant Wave Heights

Abstract Effects of new drag coefficient (Cd) parameterizations on WAVEWATCH III (WW3) model surface wave simulations are investigated. The new parameterizations are based on a coupled wind–wave model (CWW) and a wave tank experiment, and yields reduced Cd at high wind speeds. Numerical experiments for uniform winds and Hurricane Katrina (2005) indicate that the original Cd parameterization used in WW3 overestimates drag at high wind speeds compared to recent observational, theoretical, and numerical modeling results. Comparisons with buoy measurements during Hurricane Katrina demonstrate that WW3 simulations with the new Cd parameterizations yield more accurate significant wave heights compared to simulations with the original Cd parameterization, provided that accurate high-resolution wind forcing fields are used.

Reduced drag coefficient for high wind speeds in tropical cyclones

Nature ◽  
2003 ◽  
Vol 422 (6929) ◽  
pp. 279-283 ◽  
Author(s):  
Mark D. Powell ◽  
Peter J. Vickery ◽  
Timothy A. Reinhold
Keyword(s):  
Drag Coefficient ◽  
Tropical Cyclones ◽  
High Wind ◽  
Wind Speeds

scholarly journals Contribution of SAR Radar Imagery in the Study of the Dynamics of the Danube Island System, Giurgiu-Călăraşi Sector, Romania

2020 ◽  
Vol 63 (1-4) ◽  
pp. 1-6
Author(s):  
K. Hachemi ◽  
F. Grecu ◽  
G. Ioana-Toroimac ◽  
Ş. Grigorie (Omrani) ◽  
A. Ozer ◽  
...  
Keyword(s):  
Weather Conditions ◽  
Radar Signal ◽  
High Wind ◽  
Wind Speeds ◽  
Radar Images ◽  
First Results ◽  
Radar Imagery ◽  
Island System ◽  
The Stability ◽  
Very High

SAR radar imagery allows spatial and temporal, regular and precise tracking of surfaces. The response of the radar signal is particularly sensitive to the topography, the roughness and the humidity of the grounds, thus making it possible to detect possible changes occurring between different acquisitions. The surface of the islands is formed especially of alluvial materials and covered by vegetation. The latter contributes greatly to the stability of the islands. The aim of this work is to show the contribution of radar imagery in the study of the dynamics of the Danube island system, Giurgiu-Călăraşi sector, in Romania. This study, based on amplitude images, showed the possibility of determining, locating, inventorying and mapping 11 islands (including 19 sub-islands). The radar images delimit perfectly the latter due to their sensitivity to roughness. Their surface is very rough and wet represented by a strong radiometry. On the other hand, the water surface is smooth thus giving values of low radiometry. The first results obtained show that over this period between 1995 and 2009, the changes are due mainly to weather conditions, precipitation and very high wind speeds. They also reveal an increase in sediment over this 14-year period.

scholarly journals Ocean's response to Hurricane Frances and its implications for drag coefficient parameterization at high wind speeds

2009 ◽  
Vol 114 (C4) ◽  
Author(s):  
S. E. Zedler ◽  
P. P. Niiler ◽  
D. Stammer ◽  
E. Terrill ◽  
J. Morzel
Keyword(s):  
Drag Coefficient ◽  
High Wind ◽  
Wind Speeds

Rotatable shortwave curtain antenna operable at very high wind speeds

1996 ◽  
Vol 42 (1) ◽  
pp. 50-54 ◽  
Author(s):  
P. Bruger ◽  
B. Buchmann ◽  
K.-E. Kurrer ◽  
C. Ozimek
Keyword(s):  
High Wind ◽  
Wind Speeds ◽  
Very High

The Influence of wave state and sea spray on drag coefficient from low to high wind speeds

2016 ◽  
Vol 15 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Jian Shi ◽  
Zhong Zhong ◽  
Xunqiang Li ◽  
Guorong Jiang ◽  
Wenhua Zeng ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Sea Spray ◽  
High Wind ◽  
Wave State ◽  
Wind Speeds

scholarly journals A Physics-Based Parameterization of Air–Sea Momentum Flux at High Wind Speeds and Its Impact on Hurricane Intensity Predictions

2007 ◽  
Vol 135 (8) ◽  
pp. 2869-2878 ◽  
Author(s):  
Il-Ju Moon ◽  
Isaac Ginis ◽  
Tetsu Hara ◽  
Biju Thomas
Keyword(s):  
Drag Coefficient ◽  
Momentum Flux ◽  
Surface Wind ◽  
Wind Pressure ◽  
Central Pressure ◽  
Geophysical Fluid Dynamics Laboratory ◽  
High Wind ◽  
Wind Speeds ◽  
Gfdl Model ◽  
The Impact

Abstract A new bulk parameterization of the air–sea momentum flux at high wind speeds is proposed based on coupled wave–wind model simulations for 10 tropical cyclones that occurred in the Atlantic Ocean during 1998–2003. The new parameterization describes how the roughness length increases linearly with wind speed and the neutral drag coefficient tends to level off at high wind speeds. The proposed parameterization is then tested on real hurricanes using the operational Geophysical Fluid Dynamics Laboratory (GFDL) coupled hurricane–ocean prediction model. The impact of the new parameterization on the hurricane prediction is mainly found in increased maximum surface wind speeds, while it does not appreciably affect the hurricane central pressure prediction. This helps to improve the GFDL model–predicted wind–pressure relationship in strong hurricanes. Attempts are made to provide physical explanations as to why the reduced drag coefficient affects surface wind speeds but not the central pressure in hurricanes.

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