Observed drag coefficients in high winds in the near offshore of the South China Sea

Bi, Xueyan; Gao, Zhiqiu; Liu, Yangang; Liu, Feng; Song, Qingtao; Huang, Jin; Huang, Huijun; Mao, Weikang; Liu, Chunxia

doi:10.1002/2015jd023172

Cited by 34 publications

(47 citation statements)

References 46 publications

(55 reference statements)

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“…Although uncertainty of C d in high wind speeds remains large (e.g., Hsu et al, 2017, Figure 1) observations generally agree that the well-established increase of C d between 10m/s and gale-force winds (17-20 m/s) does not continue in the hurricane-force wind (>33 m/s). Some observations show that C d decreases roughly between 30 and 50 m/s (e.g., Black et al, 2007;Holthuijsen et al, 2012;Hsu et al, 2017Hsu et al, , 2019Jarosz et al, 2007;Powell et al, 2003). In other observations, C d ceases to increase at a lower wind speed around 20-22 m/s (e.g., French et al, 2007;Sanford et al, 2011).…”

Section: Introductionmentioning

confidence: 98%

“…Exchange of momentum at the air-sea interface is one of the fundamental processes that influences the tropical cyclone (TC) intensity, the associated wind hazards, and storm surges (Black et al, 2007;Emanuel, 1986;Ginis, 2002). In the TC, ocean (including storm surge), and coupled TC-ocean models, the wind stress is usually parameterized using the drag coefficient (C d ) that is a function of the 10-m neutral wind speed (corrected for stability).…”

Section: Introductionmentioning

confidence: 99%

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Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones

2020

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This study investigates the impacts of shoaling waves on the wind stress and drag coefficient (Cd) in coastal waters during tropical cyclone (TC) landfall. Numerical experiments are conducted using idealized TCs with two intensities, Category 1 and 5, and two translation speeds, 5 and 10 m/s, propagating toward and normal to the shoreline over two bottom slopes, 1:200 and 1:2000. The wave spectra are simulated using the WAVEWATCH III wave model. The unresolved high‐frequency spectral tail is parameterized as a function of wind speed, and the full wave spectrum is used to calculate the wind stress and drag coefficient. Our results show that the sea state dependence of wind stress magnitude (or Cd) is significantly increased in shallow water at a given wind speed. Compared to its deep‐water value, Cd is enhanced in the right (due to shoaling fetch‐dependent waves) and in the left (due to shoaling opposing‐wind swells) TC quadrants. However, Cd is reduced in the front/rear quadrants due to weaker wind seas. The misalignment between the wind stress and wind speed directions is enhanced in shallow water. In general, the shoaling wave effects on the wind stress and Cd are much stronger on steeper bottom slopes and in faster moving storms.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones

2020

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“…This algorithm has been used in many studies, such as in Dorman et al [17], Samelson et al [18], and Koracin et al [19], and in particular for studies of storm surge in the South China Sea (Penget et al [20] and Biet et al [21]). Figure 4 shows the peak astronomical tide of the months in 2016 and the peak of observed water levels at Vung Tau station in the period of 1987-2016.…”

Section: The Roms 2d Ocean Modelmentioning

confidence: 99%

Monsoon-Induced Surge during High Tides at the Southeast Coast of Vietnam: A Numerical Modeling Study

Nguyen¹,

Tien²,

Wettre

et al. 2019

Geosciences

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In this study, monsoon-induced surge during high tides at the Southeast coast of Vietnam was analyzed based on the observed tide data at the Vung Tau station in the period between 1997—2016. Specifically, the surge was determined by removing the astronomical tide from the observed total water level. The two-dimensional Regional Ocean Model System (ROMS 2D) was applied to simulate the surge induced by monsoons during spring tide. The surge observations showed that the change of peak surge did not follow a clear trend, of either an increase or decrease, over time. A peak surge of over 40 cm appeared mainly in October and November, although the peak of the astronomical tide was higher in December. ROMS 2D was validated with the observational data, and the model could sufficiently reproduce the wind-induced surge during high tides. This study therefor ere commends for ROMS 2D to be used in operational forecasts in this area.

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“…This mechanism fills the air with sea spray and the surface with spume, altering its frictional and roughness characteristics [35]. Many subsequent papers have studied the nonlinearity and parametrization of in these conditions (e.g., [36][37][38]). The linear fitting yields a = −1.1097 and b = 15.6995.…”

Section: Validation Ofmentioning

confidence: 99%

“…Many subsequent papers have studied the nonlinearity and parametrization of C d in these conditions (e.g., [36][37][38]). …”

Section: Validation Of C Dmentioning

confidence: 99%

Ku-Band Sea Surface Radar Backscatter at Low Incidence Angles under Extreme Wind Conditions

Zhang

Mouche

et al. 2017

Remote Sensing

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This paper reports Ku-band normalized radar cross section (NRCS) at low incidence angles ranging from 0 • to 18 • and in the wind speed range from 6 to 70 m/s. The precipitation radar onboard the tropical rainfall measuring mission and Jason-1 and 2 have provided 152 hurricanes observations between 2008 and 2013 that were collocated with stepped-frequency microwave radiometer measurements. It is found that the NRCS decreases with increasing incidence angle. The decrease is more dramatic in the 40-70 m/s range of wind speeds than in the 6-20 m/s range, indicating that the NRCS is very sensitive to low incidence angles under extreme wind conditions and insensitive to the extreme wind speed. Consequently, the sea surface appears relatively "smooth" to Ku-band electromagnetic microwaves. This phenomenon validates the observed drag coefficient reduction under extreme wind conditions, from a remote sensing viewpoint. Using the NRCS dependence on incidence angle under extreme wind conditions, we also present an empirical linear relationship between NRCS and incidence angles, which may assist future-satellites missions operating at small incidence angles to measure sea surface wind and wave field.

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Observed drag coefficients in high winds in the near offshore of the South China Sea

Cited by 34 publications

References 46 publications

Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones

Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones

Monsoon-Induced Surge during High Tides at the Southeast Coast of Vietnam: A Numerical Modeling Study

Ku-Band Sea Surface Radar Backscatter at Low Incidence Angles under Extreme Wind Conditions

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