The Dependence of Sea Surface Roughness on the Height and Steepness of the Waves

AbstractWind blowing over the ocean surface can be treated as a turbulent boundary layer over a multiscale rough surface with moving roughness elements, the waves. Large-eddy simulation (LES) of such flows is challenging because LES resolves wind–wave interactions only down to the grid scale, $\Delta $, while the effects of subgrid-scale (SGS) waves on the wind need to be modelled. Usually, a surface-layer model based on the law of the wall is used; but the surface roughness has been known to depend on the local wind and wave conditions and is difficult to parameterize. In this study, a dynamic model for the SGS sea-surface roughness is developed, with the roughness corresponding to the SGS waves expressed as ${\alpha }_{w} \hspace{0.167em} { \sigma }_{\eta }^{\Delta } $. Here, ${ \sigma }_{\eta }^{\Delta } $ is the effective amplitude of the SGS waves, modelled as a weighted integral of the SGS wave spectrum based on the geometric and kinematic properties of the waves for which five candidate expressions are examined. Moreover, ${\alpha }_{w} $ is an unknown dimensionless model coefficient determined dynamically based on the first-principles constraint that the total surface drag force or average surface stress must be independent of the LES filter scale $\Delta $. The feasibility and consistency of the dynamic sea-surface roughness models are assessed by a priori tests using data from high-resolution LES with near-surface resolution, appropriately filtered. Also, these data are used for a posteriori tests of the dynamic sea-surface roughness models in LES with near-surface modelling. It is found that the dynamic modelling approach can successfully capture the effects of SGS waves on the wind turbulence without ad hoc prescription of the model parameter ${\alpha }_{w} $. Also, for ${ \sigma }_{\eta }^{\Delta } $, a model based on the kinematics of wind–wave relative motion achieves the best performance among the five candidate models.

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A Novel Sea Surface Roughness Parameterization Based on Wave State and Sea Foam

Journal of Marine Science and Engineering ◽

10.3390/jmse9030246 ◽

2021 ◽

Vol 9 (3) ◽

pp. 246

Author(s):

Difu Sun ◽

Junqiang Song ◽

Xiaoyong Li ◽

Kaijun Ren ◽

Hongze Leng

Keyword(s):

Surface Roughness ◽

Wind Speed ◽

Drag Coefficient ◽

Sea Surface ◽

High Wind Speed ◽

Wave State ◽

Wind Speeds ◽

Sea Surface Roughness ◽

Extreme Wind ◽

The Impact

A wave state related sea surface roughness parameterization scheme that takes into account the impact of sea foam is proposed in this study. Using eight observational datasets, the performances of two most widely used wave state related parameterizations are examined under various wave conditions. Based on the different performances of two wave state related parameterizations under different wave state, and by introducing the effect of sea foam, a new sea surface roughness parameterization suitable for low to extreme wind conditions is proposed. The behaviors of drag coefficient predicted by the proposed parameterization match the field and laboratory measurements well. It is shown that the drag coefficient increases with the increasing wind speed under low and moderate wind speed conditions, and then decreases with increasing wind speed, due to the effect of sea foam under high wind speed conditions. The maximum values of the drag coefficient are reached when the 10 m wind speeds are in the range of 30–35 m/s.

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Influence of sea surface roughness on the electromagnetic wave propagation in the duct environment

2010 Second IITA International Conference on Geoscience and Remote Sensing ◽

10.1109/iita-grs.2010.5602649 ◽

2010 ◽

Cited By ~ 8

Author(s):

Xiaofeng Zhao ◽

Sixun Huang ◽

Hongjun Fan

Keyword(s):

Surface Roughness ◽

Wave Propagation ◽

Electromagnetic Wave ◽

Electromagnetic Wave Propagation ◽

Sea Surface ◽

Sea Surface Roughness

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Impact of Sea Spray and Sea Surface Roughness on the Upper Ocean Response to Super Typhoon Haitang (2005)

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0208.1 ◽

2021 ◽

Author(s):

Lianxin Zhang ◽

Xuefeng Zhang ◽

William Perrie ◽

Changlong Guan ◽

Bo Dan ◽

...

Keyword(s):

Surface Roughness ◽

Ocean Waves ◽

Sea Surface ◽

Sea Spray ◽

Upper Ocean ◽

Surface Cooling ◽

Super Typhoon ◽

Sea Surface Roughness ◽

Momentum Fluxes ◽

The Right

AbstractA coupled ocean-wave-sea spray model system is used to investigate the impacts of sea spray and sea surface roughness on the response of the upper ocean to the passage of the super typhoon Haitang. Sea spray mediated heat and momentum fluxes are derived from an improved version of Fairall’s heat fluxes formulation (Zhang et al., 2017) and Andreas’s sea spray-mediated momentum flux models. For winds ranging from low to extremely high speeds, a new parameterization scheme for the sea surface roughness is developed, in which the effects of wave state and sea spray are introduced. In this formulation, the drag coefficient has minimal values over the right quadrant of the typhoon track, along which the typhoon-generated waves are longer, smoother, and older, compared to other quadrants. Using traditional interfacial air-sea turbulent (sensible, latent, and momentum) fluxes, the sea surface cooling response to typhoon Haitang is overestimated by 1 °C, which can be compensated by the effects of sea spray and ocean waves on the right side of the storm. Inclusion of sea spray-mediated turbulent fluxes and sea surface roughness, modulated by ocean waves, gives enhanced cooling along the left edges of the cooling area by 0.2 °C, consistent with the upper ocean temperature observations.

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