Characteristic Features of a Wind Wave Field with Occasional Breaking, and Splashing Droplets at High Winds

1986 ◽  
pp. 129-145 ◽  
Author(s):  
Momoki Koga
Keyword(s):  
Wave Field ◽  
Wind Wave ◽  
Characteristic Features ◽  
High Winds

scholarly journals On Evolution of Young Wind Waves in Time and Space

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 562 ◽  
Author(s):  
Shemer
Keyword(s):  
Wave Field ◽  
Field Experiments ◽  
Wind Wave ◽  
Wind Waves ◽  
Wave Generation ◽  
Wind Forcing ◽  
Spatial And Temporal Variation ◽  
Extensive Discussion ◽  
Deterministic Theory ◽  
Theoretical Approaches

The mechanisms governing the evolution of the wind-wave field in time and in space are not yet fully understood. Various theoretical approaches have been offered to model wind-wave generation. To examine their validity, detailed and accurate experiments under controlled conditions have to be carried out. Since it is next to impossible to get the required control of the governing parameters and to accumulate detailed data in field experiments, laboratory studies are needed. Extensive previously unavailable results on the spatial and temporal variation of wind waves accumulated in our laboratory under a variety of wind-forcing conditions and using diverse measuring techniques are reviewed. The spatial characteristics of the wind-wave field were determined using stereo video imaging. The turbulent airflow above wind waves was investigated using an X-hot film. The wave field under steady wind forcing as well as evolving from rest under impulsive loading was studied. An extensive discussion of the various aspects of wind waves is presented from a single consistent viewpoint. The advantages of the stochastic approach suggested by Phillips over the deterministic theory of wind-wave generation introduced by Miles are demonstrated. Essential differences between the spatial and the temporal analyses of wind waves’ evolution are discussed, leading to examination of the applicability of possible approaches to wind-wave modeling.

Characteristics of extreme wind wave events in the Gulf of Gdańsk and associated atmospheric conditions over the Baltic Sea

2020 ◽  
Author(s):  
Aleksandra Cupial ◽  
Witold Cieslikiewicz
Keyword(s):  
Baltic Sea ◽  
Wind Velocity ◽  
Atmospheric Pressure ◽  
Wind Wave ◽  
Atmospheric Conditions ◽  
The Baltic Sea ◽  
Wave Data ◽  
Extreme Wind ◽  
Characteristic Features ◽  
The Baltic

<p>Nowadays, with possible changes in wind patterns and growing interests in the development of wind farms and other forms of renewable energy on the Baltic Sea, statistical characteristic of prevailing wave conditions at the site and changes in energy distribution, are essential. The Gulf of Gdańsk (Southern Baltic Sea) is an especially interesting area due to the presence of very characteristic long peninsula which strongly affects wave propagation and, in consequence, wave energy distribution. The objective of this work is to obtain most characteristic features of extreme storms that had significant impact on the Gulf of Gdańsk during the last half-century and associated meteorological conditions</p><p>In this study we analyse two hindcast datasets which are the result of an EU-funded project HIPOCAS (Cieślikiewicz & Paplińska-Swerpel 2008). The first one is the 44-year long reanalysis of meteorological data produced with the atmospheric model REMO (Jacob & Podzun 1997).</p><p>The second dataset used in this study is wave data produced with wave model WAM. For the modelling of waves over the Baltic Sea, a subset of gridded REMO data were extracted. Wave data have been produced in a rectangular grid in spherical rotated coordinates with the resolution 5’×5’.</p><p>The principal goal of our analysis is twofold. First, we want to estimate long-term stochastic characteristics of some basic meteorological parameters and wind wave fields. Atmospheric pressure at sea level and the wind velocity at 10 m height are analysed. As far as the wind wave data are concerned, we focus on the significant wave height (<em>H<sub>s</sub></em>), mean wave period and the mean direction of wave propagation. Secondly, this study aims to find out the characteristic features of atmospheric conditions causing extreme wind wave events in the Gulf of Gdańsk. To this end, a number of extreme storms, that are critical for a few chosen Gulf of Gdańsk regions, are selected based on <em>H<sub>s</sub></em> time series. For those selected storm periods, the storm depressions’ tracks and the overall evolution of atmospheric pressure and wind velocity fields are examined.</p><p>Our analysis showed two distinct metrological conditions that cause extreme storms in the Gulf of Gdańsk. Cyclones moving along the east side of the Baltic Sea are associated with strong northerly winds, which cause extremely high waves in the Gulf. On the other hand, cyclones travelling east in the zonal direction over the northern Baltic bring strong westerly winds. They significantly raise <em>H<sub>s</sub></em>, although not to the extent observed for the northerly winds.</p><p>In our study, we also look for the essential characteristics of the extreme meteorological conditions via results of the Empirical Orthogonal Functions (EOF) method, applied to the wind velocity vector fields.</p><p>Computations performed within this study were conducted in the TASK Computer Centre, Gdańsk with partial funding from eCUDO.pl project and the Project for Young Scientist No. 539-G210-B412-19.</p><p>Cieślikiewicz, W. & Paplińska-Swerpel, B. (2008), Coastal Engineering, <strong>55</strong>, 894–905.</p><p>Jacob, D. & Podzun, R., (1997). Meteorol. Atmos. Phys., <strong>63</strong>, 119–129.</p>

Doppler measurements of the effects of gravity waves on wind-generated ripples

1977 ◽  
Vol 81 (2) ◽  
pp. 225-240 ◽  
Author(s):  
Peter H. Y. Lee
Keyword(s):  
Frequency Shift ◽  
Wave Field ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Wind Wave ◽  
Sampling Technique ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Conditional Sampling ◽  
First Order

The effects of gravity waves on wind-generated ripples are studied experimentally by means of Doppler spectra obtained through microwave Bragg backscattering. The measurements were made at 9·23 GHz with incidence angles of between 45° and 55°. It is found from the Doppler frequency shift that an increase in the speed of Bragg waves (ripples) of wavelength approximately 2 cm can be detected when a gravity wave is propagated into a pre-existing wind-wave field. The Doppler frequency shift corresponds, to first order, to the orbital speed of the gravity wave. Further studies, using a conditional sampling technique, reveal that the Bragg scatterers are localized on the gravity wave's crest. The mechanism leading to the ‘localization’ is as yet unidentified. Ratios of gravity wavelength to Bragg (ripple) wavelength ranging from 13 to 35 have been studied.

scholarly journals Characterizing Buoy Wind Speed Error in High Winds and Varying Sea State with ASCAT and ERA5

2021 ◽  
Vol 13 (22) ◽  
pp. 4558
Author(s):  
Ethan E. Wright ◽  
Mark A. Bourassa ◽  
Ad Stoffelen ◽  
Jean-Raymond Bidlot
Keyword(s):  
Wind Speed ◽  
Wind Wave ◽  
Remote Sensing Data ◽  
Sea State ◽  
Validation Data ◽  
Speed Error ◽  
Significant Difference ◽  
High Winds ◽  
Comparison Data ◽  
High Seas

Buoys provide key observations of wind speed over the ocean and are routinely used as a source of validation data for satellite wind products. However, the movement of buoys in high seas and the airflow over waves might cause inaccurate readings, raising concern when buoys are used as a source of wind speed comparison data. The relative accuracy of buoy winds is quantified through a triple collocation (TC) exercise comparing buoy winds to winds from ASCAT and ERA5. Differences between calibrated buoy winds and ASCAT are analyzed through separating the residuals by anemometer height and testing under high wind-wave and swell conditions. First, we converted buoy winds measured near 3, 4, and 5 m to stress-equivalent winds at 10 m (U10s). Buoy U10s from anemometers near 3 m compared notably lower than buoy U10s from anemometers near 4 and 5 m, illustrating the importance of buoy choice in comparisons with remote sensing data. Using TC calibration of buoy U10s to ASCAT in pure wind-wave conditions, we found that there was a small, but statistically significant difference between height adjusted buoy winds from buoys with 4 and 5 m anemometers compared to the same ASCAT wind speed ranges in high seas. However, this result does not follow conventional arguments for wave sheltering of buoy winds, whereby the lower anemometer height winds are distorted more than the higher anemometer height winds in high winds and high seas. We concluded that wave sheltering is not significantly affecting the winds from buoys between 4 and 5 m with high confidence for winds under 18 ms−1. Further differences between buoy U10s and ASCAT winds are observed in high swell conditions, motivating the need to consider the possible effects of sea state on ASCAT winds.

Characterizing the signature of a spatio-temporal wind wave field

2018 ◽  
Vol 129 ◽  
pp. 104-123 ◽  
Author(s):  
Alvise Benetazzo ◽  
Filippo Bergamasco ◽  
Jeseon Yoo ◽  
Luigi Cavaleri ◽  
Sun-Sin Kim ◽  
...  
Keyword(s):  
Wave Field ◽  
Wind Wave ◽  
Spatio Temporal

scholarly journals Stress above Wind-Plus-Paddle Waves: Modeling of a Laboratory Experiment

2007 ◽  
Vol 37 (12) ◽  
pp. 2824-2837 ◽  
Author(s):  
V. K. Makin ◽  
H. Branger ◽  
W. L. Peirson ◽  
J. P. Giovanangeli
Keyword(s):  
Stress Distribution ◽  
Laboratory Experiment ◽  
Wave Field ◽  
Stress Level ◽  
Surface Stress ◽  
Wind Wave ◽  
Wind Waves ◽  
Wave Steepness ◽  
Low Level ◽  
Level Characteristic

Abstract A model based on wind-over-waves coupling (WOWC) theory is used to simulate a laboratory experiment and to explain the observed peculiarities of the surface stress distribution above a combined wave field: wind-generated-plus-monochromatic-paddle waves. Observations show the systematic and significant decrease in the stress as the paddle wave is introduced into the pure wind-wave field. As the paddle-wave steepness is further increased, the stress level returns to the stress level characteristic of the pure wind waves. Further increase in the paddle-wave steepness augments the stress further. The WOWC model explains this peculiarity of the stress distribution by the fact that the paddle waves significantly damp the wind waves in the spectral peak. The stress supported by these dominant waves rapidly falls when the paddle wave is introduced, and this decrease is not compensated by the stress induced by the paddle wave. With further increase in the steepness of the paddle wave, the stress supported by dominant wind waves stays at a low level while the stress supported by the paddle waves continues to grow proportional to the square of the steepness, finally exceeding the stress level characteristic of the pure wind-wave field.

Subharmonic transitions and group formation in a wind wave field

1982 ◽  
Vol 87 (C8) ◽  
pp. 5699 ◽  
Author(s):  
E. Mollo-Christensen ◽  
A. Ramamonjiarisoa
Keyword(s):  
Wave Field ◽  
Wind Wave ◽  
Group Formation
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