scholarly journals BASIC SYSTEMS OF WIND WAVE FIELD

1974 ◽  
Vol 1 (14) ◽  
pp. 12
Author(s):  
Yu. M. Krylov ◽  
S.S. Strekalov ◽  
V. Ph. Tsyloukhin
Keyword(s):  
Wind Speed ◽  
Continuous Wave ◽  
System Development ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Phase Speed ◽  
Typical Feature ◽  
Sea Waves ◽  
First Results ◽  
Energy Maximum

The study of wind waves is usually carried out in the following manner. At the first moment a homogenous wind field with the constant speed directed from the shore to the basin is occurred over the water surface restricted by a straight shore line. It is required to calculate statistic wave characteristics as functions of time and distance from the shore. When solving the problem in such a way the explorers [.1-6 ~] usually came to a conclusion of the system development of gravitational waves with a main energy maximum the amplitude and period of which rise in process developing from small magnitudes to limiting values. Some explorers noted that the two -or three-wave systems under the conditions of constant wind are available. The first results of this theory were obtained by L.Ph. Tytov. In studies of stereophotographs of sea waves he noted and described quantitatively two types of waves: "prevailing" and "large", f7l I* is possible to show that the first type of waves has a phase speed that is less than wind speed, and the second one is equal to wind speed. At a later time G.Neumann [6J generalizing results of ocean observations has come to the conclusion that under the action of constant wind three "specific" wave systems which have phase speeds less, equal and 1.2 more than the speed of wind are developed. However, Tytov's and Neumann's results didn't receive a progress, and later on they were substituted by the conception of continuous wave spectrum with one energy maximum £3-6J • Nevertheless, the opinions of availability of two-or three-wave systems as a typical feature of wind rough sea [8,9] were published in the press.

FPSO Transient Responses During Cyclonic Storms

2007 ◽  
Author(s):  
Dusan Curic ◽  
Yong Luo
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Wind Waves ◽  
Rapid Change ◽  
Line Tension ◽  
Green Water ◽  
Mooring Line ◽  
Sea Waves ◽  
Transient Responses ◽  
Cyclonic Storm

This paper presents the key results and conclusions of the study of FPSO transient responses in the cyclonic storm. The measured wind, wave and current data of recent cyclonic events are utilized to simulate the FPSO responses in terms of mooring loads, vessel yaw motion and relative FPSO heading to waves as it weathervanes in the wind, waves and current, input as time series. The primary objectives are to check the FPSO responses as the cyclone (eye or fringe) passes over it, causing rapid changes in the intensity and the direction of environmental loads, and to confirm the adequacy of the present mooring system design criteria. The results of the study serve as a good benchmark of the current industry standard for mooring design and address industry’s concern of the safety of FPSO platforms in the event of cyclonic storm. This study has used the hindcast data to inspect the event of a strong cyclonic storm passing over an FPSO. Despite the fact that the wind direction changes for about 140° in only one hour in the path of the cyclone eye, higher mooring line tension has not been observed due to reduced wind speed in the eye of the storm. The extreme mooring line tension is still governed by the responses in the path of cyclone fringe due to its maximum wind speed. Note that the transient analysis has shown that, during the rapid change of wind direction, the vessel can potentially be exposed to beam sea waves. Although this does not correspond with the highest tension in mooring legs, it can lead to critical green water impact.

scholarly journals A Note on the Ocean Surface Roughness Spectrum*

2011 ◽  
Vol 28 (3) ◽  
pp. 436-443 ◽  
Author(s):  
Paul A. Hwang
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Power Law ◽  
Field Data ◽  
Wave Spectrum ◽  
Phase Speed ◽  
Short Wave ◽  
Wave Number ◽  
Power Law Function ◽  
Good Agreement

Abstract In a recent study, the dimensionless surface roughness spectrum has been empirically parameterized as a power-law function of the dimensionless wind speed expressed as the ratio of wind friction velocity and phase speed of the surface roughness wave component. The wave-number-dependent proportionality coefficient, A, and exponent, a, of the power-law function are derived from field measurements of the short-wave spectrum. To extend the roughness spectrum model beyond the wavenumber range of field data, analytical functions are formulated such that A and a approach their asymptotic limits: A0 and a0 toward the lowest wavenumber, and A∞ and a∞ toward the highest wavenumber. Of the four asymptotic values, A∞ is considered most questionable for the lack of reference information. When applied to the normalized radar cross-section (NRCS) computation, the results are in good agreement (within about 2 dB) with field data or geophysical model functions (GMFs) for incidence angles between 20° and 40° but significant underestimation occurs for higher incidence angles. The comparison study of NRCS computation offers helpful guidelines for adjusting the asymptotic factors, especially the numerical value of A∞. Improved agreement between the computed NRCS (vertical polarization) using the new roughness spectrum with GMF is expanded to incidence angles between 20° and 60°. The wind speed range of good agreement between calculation and GMF is below about 15 m s−1 for Ku band and about 30 m s−1 for C band.

Wind speed data analysis for predictions of sea waves in Bitung Coastal Waters

2013 ◽  
pp. 35 ◽  
Author(s):  
Joanes E Koagouw ◽  
Gybert E Mamuaya ◽  
Adrie A Tarumingkeng ◽  
P A Angmalisang
Keyword(s):  
Data Analysis ◽  
Wind Speed ◽  
Coastal Waters ◽  
Transition Period ◽  
Marine Resources ◽  
Land Uses ◽  
Sea Waves ◽  
North West ◽  
North Sulawesi ◽  
The Waves

Coastal area of Bitung Municipality is one of the economical activities centers in North Sulawesi Province such as for land-uses and the exploitation of natural resources. Those activities are exaggerating day bay day and tended to be uncontrollable. The excess of those conditions, it has been recorded the change of waves in Bitung waters that has impacts to coastal areas and can affect the utilization of coastal and marine resources. This research was aimed to observe waves altitude variations in Bitung waters with Svedrup Munk and Bretchsneider (SMB) method that had been used to predict waves altitudes. The results showed that the wind speed during West Season was 0.33 m and were dominant to the East, while during East season was 0.91m from South-East to North-West, and then on transition period (March to May) was 1.08m from South-East to East. The results of those wind speed to the waves altitudes in Bitung waters is discussed in this paper© Pesisir pantai Kota Bitung merupakan salah satu pusat aktivitas ekonomi (misalnya pemanfaatan lahan dan eksploitasi sumberdaya) di Provinsi Sulawesi Utara. Aktivitas tersebut semakin hari semakin meningkat dan memiliki kecenderungan tidak terkontrol. Akibat dari keadaan tersebut, telah terjadi perubahan fenomena gelombang di perairan Bitung yang berdampak pada keberadaan daerah pesisir pantai di mana hal ini dapat mengganggu aktivitas pemanfaatan sumberdaya pesisir dan laut tersebut. Penelitian ini bertujuan untuk mengetahui variasi tinggi gelombang di perairan Bitung dengan menggunakan metode Svedrup Munk and Bretchsneider (SMB) yang biasa digunakan untuk peramalan tinggi gelombang signifikan. Hasil penelitian menunjukkan bahwa kecepatan angin pada Musim Barat sebesar 0,33 meter dan dominan ke arah Timur, sementara pada Musim Timur sebesar 0,91 meter dari arah Tenggara ke Barat Laut, serta pada Musim Peralihan (antara bulan Maret-Mei) adalah sebesar 1,08 meter dari arah Tenggara dan Timur. Pengaruh kecepatan angin tersebut terhadap gelombang laut di perairan Bitung dibahas dalam tulisan ini©

Wave Breaking Dissipation in a Young Wind Sea

2014 ◽  
Vol 44 (1) ◽  
pp. 104-127 ◽  
Author(s):  
Michael Schwendeman ◽  
Jim Thomson ◽  
Johannes R. Gemmrich
Keyword(s):  
Wind Waves ◽  
Phase Speed ◽  
Field Studies ◽  
Turbulent Energy ◽  
Strength Parameter ◽  
Video Recordings ◽  
Sonar System ◽  
Wind Sea ◽  
Equilibrium Range

Abstract Coupled in situ and remote sensing measurements of young, strongly forced wind waves are applied to assess the role of breaking in an evolving wave field. In situ measurements of turbulent energy dissipation from wave-following Surface Wave Instrument Float with Tracking (SWIFT) drifters and a tethered acoustic Doppler sonar system are consistent with wave evolution and wind input (as estimated using the radiative transfer equation). The Phillips breaking crest distribution Λ(c) is calculated using stabilized shipboard video recordings and the Fourier-based method of Thomson and Jessup, with minor modifications. The resulting Λ(c) are unimodal distributions centered around half of the phase speed of the dominant waves, consistent with several recent studies. Breaking rates from Λ(c) increase with slope, similar to in situ dissipation. However, comparison of the breaking rate estimates from the shipboard video recordings with the SWIFT video recordings show that the breaking rate is likely underestimated in the shipboard video when wave conditions are calmer and breaking crests are small. The breaking strength parameter b is calculated by comparison of the fifth moment of Λ(c) with the measured dissipation rates. Neglecting recordings with inconsistent breaking rates, the resulting b data do not display any clear trends and are in the range of other reported values. The Λ(c) distributions are compared with the Phillips equilibrium range prediction and previous laboratory and field studies, leading to the identification of several inconsistencies.

scholarly journals Doppler wind lidar activities at Cabauw

2021 ◽  
Author(s):  
Steven Knoop ◽  
Fred Bosveld ◽  
Marijn de Haij ◽  
Arnoud Apituley
Keyword(s):  
Wind Speed ◽  
Wind Profile ◽  
Continuous Wave ◽  
Wind Farms ◽  
Data Availability ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Low Clouds ◽  
Wind Measurements ◽  
Wind Lidar

<p>Atmospheric motion and turbulence are essential parameters for weather and topics related to air quality. Therefore, wind profile measurements play an important role in atmospheric research and meteorology. One source of wind profile data are Doppler wind lidars, which are laser-based remote sensing instruments that measure wind speed and wind direction up to a few hundred meters or even a few kilometers. Commercial wind lidars use the laser wavelength of 1.5 µm and therefore backscatter is mainly from aerosols while clear air backscatter is minimal, limiting the range to the boundary layer typically.</p><p>We have carried out a two-year intercomparison of the ZephIR 300M (ZX Lidars) short-range wind lidar and tall mast wind measurements at Cabauw [1]. We have focused on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213m tall meteorological mast. We have found an overall availability of quality-controlled wind lidar data of 97% to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm/h or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m/s with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. This instrument is being deployed within North Sea wind farms.</p><p>Recently, a scanning long-range wind lidar Windcube 200S (Leosphere/Vaisala) has been installed at Cabauw, as part of the Ruisdael Observatory program [2]. The scanning Doppler wind lidars will provide detailed measurements of the wind field, aerosols and clouds around the Cabauw site, in coordination with other instruments, such as the cloud radar.</p><p>[1] Knoop, S., Bosveld, F. C., de Haij, M. J., and Apituley, A.: A 2-year intercomparison of continuous-wave focusing wind lidar and tall mast wind measurements at Cabauw, Atmos. Meas. Tech., 14, 2219–2235, 2021</p><p>[2] https://ruisdael-observatory.nl/</p>

Scanning laser wave recorder with registration of “instantaneous” sea surface profiles

2021 ◽  
Author(s):  
V.V. Sterlyadkin ◽  
K.V. Kulikovsky ◽  
A.V. Kuzmin ◽  
E.A. Sharkov ◽  
M.V. Likhacheva
Keyword(s):  
Spatial Scales ◽  
Wind Waves ◽  
Single Point ◽  
Video Recording ◽  
Surface Profile ◽  
Weather Conditions ◽  
Sea Surface ◽  
Sea Waves ◽  
Wide Range ◽  
Wave Recorder

AbstractA direct optical method for measuring the “instantaneous” profile of the sea surface with an accuracy of 1 mm and a spatial resolution of 3 mm is described. Surface profile measurements can be carried out on spatial scales from units of millimeters to units of meters with an averaging time of 10−4 s. The method is based on the synchronization of the beginning of scanning a laser beam over the sea surface and the beginning of recording the radiation scattered on the surface onto the video camera matrix. The heights of all points of the profile are brought to a single point in time, which makes it possible to obtain “instantaneous” profiles of the sea surface with the frequency of video recording. The measurement technique and data processing algorithm are described. The errors of the method are substantiated. The results of field measurements of the parameters of sea waves are presented: amplitude spectra, distribution of slopes at various spatial averaging scales. The applied version of the wave recorder did not allow recording capillary oscillations, but with some modernization it will be possible. The method is completely remote, does not distort the properties of the surface, is not affected by wind, waves and sea currents, it allows you to measure the proportion of foam on the surface. The possibility of applying the proposed method at any time of the day and in a wide range of weather conditions has been experimentally proved.

Covariate Extreme Value Analysis Using Wave Spectral Partitioning

2020 ◽  
Vol 37 (5) ◽  
pp. 873-888 ◽  
Author(s):  
Jesús Portilla-Yandún ◽  
Edwin Jácome
Keyword(s):  
Extreme Values ◽  
Wind Waves ◽  
Spectral Energy Distribution ◽  
Wave Spectrum ◽  
Wave Climate ◽  
Extreme Value ◽  
Extreme Value Analysis ◽  
Spectral Energy ◽  
Value Analysis ◽  
Spectral Partitioning

AbstractAn important requirement in extreme value analysis (EVA) is for the working variable to be identically distributed. However, this is typically not the case in wind waves, because energy components with different origins belong to separate data populations, with different statistical properties. Although this information is available in the wave spectrum, the working variable in EVA is typically the total significant wave height Hs, a parameter that does not contain information of the spectral energy distribution, and therefore does not fulfill this requirement. To gain insight in this aspect, we develop here a covariate EVA application based on spectral partitioning. We observe that in general the total Hs is inappropriate for EVA, leading to potential over- or underestimation of the projected extremes. This is illustrated with three representative cases under significantly different wave climate conditions. It is shown that the covariate analysis provides a meaningful understanding of the individual behavior of the wave components, in regard to the consequences for projecting extreme values.

scholarly journals 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

2003 ◽  
Vol 21 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
C. Haldoupis ◽  
A. Bourdillon ◽  
A. Kamburelis ◽  
G. C. Hussey ◽  
J. A. Koehler
Keyword(s):  
Electric Fields ◽  
Continuous Wave ◽  
Isotropic Turbulence ◽  
Doppler Radar ◽  
Active Regions ◽  
Field Of View ◽  
Ionosphere Plasma ◽  
First Results ◽  
Sporadic E

Abstract. In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment), a bistatic 50 MHz continuous wave (CW) Doppler radar located on the island of Crete, Greece, to a single (east-west) baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP) echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities)

scholarly journals The Transition from Downward to Upward Air–Sea Momentum Flux in Swell-Dominated Light Wind Conditions

2018 ◽  
Vol 75 (8) ◽  
pp. 2579-2588 ◽  
Author(s):  
Ulf Högström ◽  
Erik Sahlée ◽  
Ann-Sofi Smedman ◽  
Anna Rutgersson ◽  
Erik Nilsson ◽  
...  
Keyword(s):  
Wind Speed ◽  
Momentum Flux ◽  
Water Surface ◽  
Sea Waves ◽  
Progressive Wave ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Light Wind ◽  
Wind Sea ◽  
Almost All

Abstract Fifteen hours of consecutive swell data from the experiment Flux, État de la Mer, et Télédétection en Condition de Fetch Variable (FETCH) in the Mediterranean show a distinct upward momentum flux. The characteristics are shown to vary systematically with wind speed. A hysteresis effect is found for wave energy of the wind-sea waves when represented as a function of wind speed, displaying higher energy during decaying winds compared to increasing winds. For the FETCH measurements, the upward momentum transfer regime is found to begin for wind speeds lower than about U = 4 m s−1. For the lowest observed wind speeds U < 2.4 m s−1, the water surface appears to be close to dynamically smooth. In this range almost all the upward momentum flux is accomplished by the peak in the cospectrum between the vertical and horizontal components of the wind velocity. It is demonstrated that this contribution in turn is linearly related to the swell significant wave height Hsd in the range 0.6 < Hsd < 1.4 m. For Hsd < 0.6 m, the contribution is zero in the present dataset but may depend on the swell magnitude in other situations. It is speculated that the observed upward momentum flux in the smooth regime, which is so strongly related to the cospectral peak at the dominant swell frequency, might be caused by the recirculation mechanism found by Wen and Mobbs in their numerical simulation of laminar flow of a nonlinear progressive wave at low wind speed.

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