Variations in sea surface roughness induced by the 2004 Sumatra-Andaman tsunami

Abstract. Observations of tsunamis away from shore are critically important for improving early warning systems and understanding of tsunami generation and propagation. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude there is much smaller than it is close to shore. Currently, tsunami observations in deep water rely on measurements of variations in the sea surface height or bottom pressure. Here we demonstrate that there exists a different observable, specifically, ocean surface roughness, which can be used to reveal tsunamis away from shore. The first detailed measurements of the tsunami effect on sea surface height and radar backscattering strength in the open ocean were obtained from satellite altimeters during passage of the 2004 Sumatra-Andaman tsunami. Through statistical analyses of satellite altimeter observations, we show that the Sumatra-Andaman tsunami effected distinct, detectable changes in sea surface roughness. The magnitude and spatial structure of the observed variations in radar backscattering strength are consistent with hydrodynamic models predicting variations in the near-surface wind across the tsunami wave front. Tsunami-induced changes in sea surface roughness can be potentially used for early tsunami detection by orbiting microwave radars and radiometers, which have broad surface coverage across the satellite ground track.

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Detection of the 2010 Chilean tsunami using satellite altimetry

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-2391-2011 ◽

2011 ◽

Vol 11 (9) ◽

pp. 2391-2406 ◽

Cited By ~ 4

Author(s):

B. D. Hamlington ◽

R. R. Leben ◽

O. A. Godin ◽

J. F. Legeais ◽

E. Gica ◽

...

Keyword(s):

Surface Roughness ◽

Early Warning ◽

Early Warning System ◽

Warning System ◽

Sea Surface Height ◽

Open Ocean ◽

Sea Surface ◽

Sea Surface Roughness ◽

Spatial Coverage ◽

Chilean Tsunami

Abstract. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude is much smaller than it is closer to shore. An effective early warning system, however, must be able to observe an impending tsunami threat far away from the shore in order to provide the necessary lead-time for coastal inhabitants to find safety. Given the expansiveness of the ocean, sensors capable of detecting the tsunami must also have very broad areal coverage. The 2004 Sumatra-Andaman tsunami was definitively detected in the open ocean from both sea surface height and sea surface roughness measurements provided by satellite altimeters. This tsunami, however, was exceptionally strong and questions remain about the ability to use such measurements for the detection of weaker tsunamis. Here we study the 2010 Chilean tsunami and demonstrate the ability to detect the tsunami in the open ocean. Specifically, we analyze the utility of filtering in extracting the tsunami signal from sea surface height measurements, and, through the use of statistical analyses of satellite altimeter observations, we demonstrate that the 2010 Chilean tsunami induced distinct and detectable changes in sea surface roughness. While satellite altimeters do not provide the temporal and spatial coverage necessary to form the basis of an effective early warning system, tsunami-induced changes in sea surface roughness can be detected using orbiting microwave radars and radiometers, which have a broad surface coverage across the satellite ground track.

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Sea Surface Roughness Observed by High Resolution Radar

Remote Sensing ◽

10.3390/rs11172026 ◽

2019 ◽

Vol 11 (17) ◽

pp. 2026 ◽

Cited By ~ 1

Author(s):

Atsushi Fujimura ◽

Susanne Lehner ◽

Alexander Soloviev ◽

Xiaofeng Li

Keyword(s):

Surface Roughness ◽

High Resolution ◽

Wind Field ◽

Surface Wind ◽

Sea Surface ◽

Sea Surface Wind ◽

Sea Surface Roughness ◽

High Resolution Radar ◽

Surface Wind Field

Changes in the sea surface roughness are usually associated with a change in the sea surface wind field [...]

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Dynamic modelling of sea-surface roughness for large-eddy simulation of wind over ocean wavefield

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.215 ◽

2013 ◽

Vol 726 ◽

pp. 62-99 ◽

Cited By ~ 35

Author(s):

Di Yang ◽

Charles Meneveau ◽

Lian Shen

Keyword(s):

Surface Roughness ◽

Large Eddy Simulation ◽

Wind Wave ◽

Dynamic Modelling ◽

Sea Surface ◽

Near Surface ◽

Eddy Simulation ◽

Sea Surface Roughness ◽

Large Eddy ◽

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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Wind Stress Over Waves: Effects of Sea Roughness and Atmospheric Stability

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.1488933 ◽

2002 ◽

Vol 124 (3) ◽

pp. 169-172 ◽

Cited By ~ 2

Author(s):

Dag Myrhaug ◽

Olav H. Slaattelid

Keyword(s):

Boundary Layer ◽

Wind Stress ◽

Local Equilibrium ◽

Surface Wind ◽

Atmospheric Stability ◽

Sea Surface ◽

Stability Function ◽

Sea Surface Wind ◽

Surface Wind Stress ◽

Sea Surface Roughness

The paper considers the effects of sea roughness and atmospheric stability on the sea surface wind stress over waves, which are in local equilibrium with the wind, by using the logarithmic boundary layer profile including a stability function, as well as adopting some commonly used sea surface roughness formulations. The engineering relevance of the results is also discussed.

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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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Arctic sea surface height maps from multi-altimeter combination

10.5194/essd-2021-123 ◽

2021 ◽

Author(s):

Pierre Prandi ◽

Jean-Christophe Poisson ◽

Yannice Faugère ◽

Amandine Guillot ◽

Gérald Dibarboure

Keyword(s):

Sea Level ◽

Sea Surface Height ◽

Open Ocean ◽

Sea Surface ◽

Optimal Interpolation ◽

Independent Data ◽

Interpolation Scheme ◽

Sea Level Anomaly ◽

Arctic Sea ◽

The Cross

Abstract. We present a new Arctic sea level anomaly dataset, based on the combination of three altimeter missions using an optimal interpolation scheme. Measurements from SARAL/AltiKa, CryoSat-2 and Sentinel-3A are blended together providing an unprecedented resolution for this type of products. The ﬁnal gridded ﬁelds cover all latitudes north of 50° N, on a 25 km EASE2 grid, with one grid every three days over three years from July 2016 to April 2019. We use the Adaptive retracker to process both open ocean and lead echoes on SARAL/AltiKa thus removing the need to estimate a bias between open ocean an ice covered areas. SARAL/AltiKa also provides the baseline for the cross-calibation of CryoSat-2 and Sentinel-3A data. When compared to independent data, the combined product exhibits a much better performance than previously available datasets based on the analysis of a single mission.

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