On the wave age dependence of wind stress over pure wind seas

Drennan, William M.; Graber, Hans C.; Hauser, Danièle; Quentin, Céline Gwenaëlle

doi:10.1029/2000jc000715

Cited by 307 publications

(465 citation statements)

References 44 publications

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“…[38] For wind-sea-dominated conditions (solid dots in Figure 10) the expected increasing roughness for younger waves can be seen, but roughness values are smaller than those expected for pure wind sea conditions using the Drennan et al [2003] relationship (dashed line in Figure 9. Inverse wave age (u * /C p ) of wind generated waves versus neutral wind speed for high winds.…”

Section: Strong Wind Eventsmentioning

confidence: 99%

“…This criterion is commonly used to define ''pure wind sea'' conditions [e.g., Drennan et al, 2003Drennan et al, , 2005. However, the use of the term ''wind-seadominated'' conditions is preferred in this study, since the criterion E ws > 5E s does not explicitly preclude the presence of swell.…”

Section: Strong Wind Eventsmentioning

confidence: 99%

“…Under these conditions the wind-generated waves were underdeveloped and became younger as the wind speed increased (Figure 9). Underdeveloped waves are expected to be rougher than their fully developed counterparts and therefore an increase of C D is expected [Drennan et al, 2003].…”

Section: Strong Wind Eventsmentioning

confidence: 99%

“…Lines represent the mean value for wind-sea-dominated conditions (solid line), the universal spectral shape of Miyake et al [1970] (dashed line), and the inertial subrange slope (dotted line). observed parameters, using the Drennan et al [2003] relationship. Then, C Dpws was obtained from (2).…”

Section: Strong Wind Eventsmentioning

confidence: 99%

“…[3] Several studies have shown a dependence of the sea drag coefficient on the degree of development of the wind waves and have proposed parameterizations of z 0 in terms of wave age C p /U 10 , the ratio between wave phase velocity C p and wind speed U 10 ; or alternatively C p /u * , where u * is the friction velocity [e.g., Donelan, 1990;Drennan et al, 2003]. Although these formulae seem to describe adequately the wind stress in pure wind sea conditions, it has been shown that the presence of swell obscures the relationship between roughness and wave age [Drennan et al, 2005] reducing its applicability.…”

Section: Introductionmentioning

confidence: 99%

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Wind stress in the presence of swell under moderate to strong wind conditions

et al. 2009

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[1] Wind stress is a key parameter for oceanic and atmospheric modeling, forecasting, and hydrodynamic studies. It is generally accepted that wind stress depends on the sea state. In particular, it has been shown that the presence of swell can modify both magnitude and direction of the wind stress. The presence of swell enhances momentum flux when swell propagates opposite to the wind direction and reduces it when it travels along the wind direction. However, those conclusions are mainly based on data acquired in low wind speed conditions and it is not clear to what extent an effect of swell persists at higher winds. Here simultaneous measurements of wind stress and waves, carried out in an area characterized by the occurrence of strong offshore winds with counter long-period swell, are presented and analyzed. The observations indicate that swell causes substantial changes to the wind stress at all observed wind conditions, including wind speeds as high as 20 ms À1 . It is believed that in low wind conditions swell increases drag by directly interacting with the air flow, whereas at higher winds, swell reduces drag by modifying the wind-sea-associated roughness.Citation: García-Nava, H., F. J. Ocampo-Torres, P. Osuna, and M. A. Donelan (2009), Wind stress in the presence of swell under moderate to strong wind conditions,

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Section: Strong Wind Eventsmentioning

confidence: 99%

Section: Strong Wind Eventsmentioning

confidence: 99%

Section: Strong Wind Eventsmentioning

confidence: 99%

Section: Strong Wind Eventsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Wind stress in the presence of swell under moderate to strong wind conditions

et al. 2009

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Direct measurements of wind stress over the surf zone

Shabani

Nielsen

Baldock

2014

J. Geophys. Res. Oceans

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Field data of the wind stress over surf zone waves are presented from an open ocean beach on the East Australian Coast. Two ultrasonic anemometers were deployed at nominal heights of 5 and 10 m above the water surface in the intertidal and inner surf zones, with concurrent measurements of water levels and offshore wave parameters. Following a rigorous quality control procedure, the wind stress was determined by the eddy correlation technique. A constant stress layer was observed between 5 and 10 m elevation. Considering nearneutral conditions only, the wind drag coefficients were found to systematically change with the wind angle of approach relative to the shoreline and are much smaller for longshore wind than during onshore wind. The concept of an apparent wave steepness changing with wind direction is suggested to explain this behavior. The drag coefficients over the surf zone during onshore wind and near-neutral conditions were determined to be almost twice the values expected at the same wind speed and open ocean conditions. The observed Charnock coefficient was similarly an order of magnitude larger than open ocean values. A wave celerity of the order of that expected in the inner surf zone is required to explain the observed large roughness and drag coefficients using existing wave age-dependent parameterizations. This suggests that the slower wave celerity in the surf zone is an important contributor to the increased wind stress, in addition to the sawtooth wave shape.

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Spectral form and source term balance of short gravity wind waves

Tamura

Drennan

Graber

2014

J. Geophys. Res. Oceans

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We investigated the spectral structure and source term balance of short gravity waves, based on in situ observations of wave number spectra retrieved by air-sea interaction spar (ASIS) buoys. The behaviors of wave number spectra up to 10 rad/m (the gravity wave regime) were analyzed for a wide range of wind and wave conditions. The observed wave number spectra showed the spectral power laws described by Toba (1973) and Phillips (1958) in addition to the characteristic nodal point at $10 rad/m where spectral energy becomes constant over the entire wind speed range. We also improved the thirdgeneration wave model using the nonlinear dissipation term. The wave model reproduced the spectral form in the higher wave number domain. In the equilibrium range, nonlinear transfer played a major role in maintaining equilibrium conditions. On the other hand, in the saturation range, which starts at the upper limit of the equilibrium range, the nonlinear transfer tended to be out of balance with other source terms, and the dissipation term was in balance with wind input.

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On the wave age dependence of wind stress over pure wind seas

Cited by 307 publications

References 44 publications

Wind stress in the presence of swell under moderate to strong wind conditions

Wind stress in the presence of swell under moderate to strong wind conditions

Direct measurements of wind stress over the surf zone

Spectral form and source term balance of short gravity wind waves

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