Shipboard Measurement of Ocean Waves

2011 ◽  
Author(s):  
Thomas C. Fu ◽  
Anne M. Fullerton ◽  
Erin E. Hackett ◽  
Craig Merrill
Keyword(s):  
Field Tests ◽  
Ocean Waves ◽  
Naval Research ◽  
Wave Spectra ◽  
Individual Measurement ◽  
Office Of Naval Research ◽  
Wave Radar ◽  
New Instrumentation ◽  
Directional Wave ◽  
Commercial Off The Shelf

Over the past several years a number of techniques have been utilized for the measurement of ocean waves from shipboard platforms. These systems have ranged from commercial off the shelf (COTS) navigation radar and Light Detection and Ranging (LIDAR) systems to specially developed in-house instrumentation systems. Most of these systems have been utilized to measure the directional wave spectra around the ship. More recently, the Naval Surface Warfare Center, Carderock Division (NSWCCD) and others have begun to utilize these techniques for shipboard measurement of individual ship generated waves as well as open ocean waves. NSWCCD has used a number of these methods on various Office of Naval Research (ONR) and Naval Sea Systems (NAVSEA) sponsored field tests. These field tests were performed on a variety of naval platforms over a range of sizes, including some fixed platforms, for various sea states. While each of these tests has had individual measurement goals and objectives, the series of tests has also provided an environment for testing and developing new instrumentation and exploring their capabilities. As a result of these efforts, instrumentation has grown in sophistication from qualitative video-based observations of the wave field around an underway vessel to laser and radar based imaging and ranging measurements of free surface dynamics. This work has led to higher fidelity data, as well as data that were previously unobtainable. In this paper we provide an overview of these systems and techniques and summarize the basic capabilities of each method by providing measurement examples/applications. These systems include a shipboard array of ultrasonic distance sensors for measuring directional wave spectra, a COTS wave radar system, and a COTS scanning LIDAR system. While not intending to be exhaustive, this paper seeks to highlight the insights gained from the recent applications of these techniques, as well as the difficulties and issues associated with shipboard measurements such as ship motion and logistical constraints.

Simulation of Hurricane Seas in a Multidirectional Wave Basin

1991 ◽  
Vol 113 (3) ◽  
pp. 219-227 ◽  
Author(s):  
A. Cornett ◽  
M. D. Miles
Keyword(s):  
Ocean Waves ◽  
Entropy Method ◽  
Wave Spectra ◽  
Single Wave ◽  
Wave Condition ◽  
Wave Basin ◽  
Wide Range ◽  
Directional Wave ◽  
Wave Conditions ◽  
Multidirectional Wave

This paper describes the generation and verification of four realistic sea states in a multidirectional wave basin, each representing a different storm wave condition in the Gulf of Mexico. In all cases, the degree of wave spreading and the mean direction of wave propagation are strongly dependent on frequency. Two of these sea states represent generic design wave conditions typical of hurricanes and winter storms and are defined by JONSWAP wave spectra and parametric spreading functions. Two additional sea states, representing the specific wave activity during hurricanes Betsy and Carmen, are defined by tabulated hindcast estimates of the directional wave energy spectrum. The Maximum Entropy Method (MEM) of directional wave analysis paired with a single-wave probe/ bi-directional current meter sensor is found to be the most satisfactory method to measure multidirectional seas in a wave basin over a wide range of wave conditions. The accuracy of the wave generation and analysis process is verified using residual directional spectra and numerically synthesized signals to supplement those measured in the basin. Reasons for discrepancy between the measured and target directional wave spectra are explored. By attempting to reproduce such challenging sea states, much has been learned about the limitations of simulating real ocean waves in a multidirectional wave basin, and about techniques which can be used to minimize the associated distortions to the directional spectrum.

Wave-Coherent Airflow and Critical Layers over Ocean Waves

2013 ◽  
Vol 43 (10) ◽  
pp. 2156-2172 ◽  
Author(s):  
Laurent Grare ◽  
Luc Lenain ◽  
W. Kendall Melville
Keyword(s):  
Momentum Flux ◽  
Wave Spectrum ◽  
Phase Speed ◽  
Ocean Waves ◽  
Naval Research ◽  
Critical Height ◽  
Office Of Naval Research ◽  
Mean Wind Speed ◽  
Wave Induced ◽  
The Waves

Abstract An analysis of coherent measurements of winds and waves from data collected during the Office of Naval Research (ONR) High-Resolution air–sea interaction (HiRes) program, from the Floating Instrument Platform (R/P FLIP), off the coast of northern California in June 2010 is presented. A suite of wind and wave measuring systems was deployed to resolve the modulation of the marine atmospheric boundary layer by waves. Spectral analysis of the data provided the wave-induced components of the wind velocity for various wind–wave conditions. The power spectral density, the amplitude, and the phase (relative to the waves) of these wave-induced components are computed and bin averaged over spectral wave age c/U(z) or c/u*, where c is the linear phase speed of the waves, U(z) is the mean wind speed measured at the height z of the anemometer, and u* is the friction velocity in the air. Results are qualitatively consistent with the critical layer theory of Miles. Across the critical height zc, defined such that U(zc) = c, the wave-induced vertical and horizontal velocities change significantly in both amplitude and phase. The measured wave-induced momentum flux shows that, for growing waves, less than 10% of the momentum flux at z ≈ 10 m is supported by waves longer than approximately 15 m. For older sea states, these waves are able to generate upward wave-induced momentum flux opposed to the overall downward momentum flux. The measured amplitude of this upward wave-induced momentum flux was up to 20% of the value of the total wind stress when Cp/u* > 60, where Cp is the phase speed at the peak of the wave spectrum.

scholarly journals Measuring Ocean Waves From Space: Objectives and Characteristics of the China-France Oceanography SATellite (CFOSAT)

2010 ◽  
Author(s):  
Danie`le Hauser ◽  
Ce´line Tison ◽  
Jean-Michel Lefe`vre ◽  
Juliette Lambin ◽  
Amiot Thierry ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Ocean Surface ◽  
Ocean Waves ◽  
Wave Spectra ◽  
Wind Vector ◽  
Satellite Mission ◽  
Surface Ocean ◽  
Related Science ◽  
Directional Wave ◽  
Ku Band

The Chinese and French Space Agencies are jointly preparing a satellite mission devoted to the monitoring of the ocean surface and related science and applications. This is the so-called “China France Oceanography SATellite” (CFOSAT), to be launched around 2013. This mission will provide simultaneous and collocated observations of wind at the ocean surface and spectral properties of surface ocean waves using two scatterometers, both in Ku-Band: SWIM for measurements of directional wave spectra and SCAT for wind vector measurements. The SWIM instrument will use a real aperture observation technique so as to avoid limitations encountered with SAR systems. This paper describes the main objectives and characteristics of the mission with a focus on the SWIM instrument designed and developed under French responsibility to measure directional spectra of ocean waves.

scholarly journals Simultaneous Measurement of Ocean Winds and Waves with an Airborne Coherent Real Aperture Radar

2005 ◽  
Vol 22 (7) ◽  
pp. 832-846 ◽  
Author(s):  
William J. Plant ◽  
William C. Keller ◽  
Kenneth Hayes
Keyword(s):  
Wind Speed ◽  
Cross Sections ◽  
Ocean Surface ◽  
Naval Research ◽  
Wave Spectra ◽  
Received Power ◽  
Ocean Winds ◽  
Directional Wave ◽  
Real Aperture Radar ◽  
Aperture Radar

Abstract A coherent, X-band airborne radar has been developed to measure wind speed and direction simultaneously with directional wave spectra on the ocean. The coherent real aperture radar (CORAR) measures received power, mean Doppler shifts, and mean Doppler bandwidths from small-resolution cells on the ocean surface and converts them into measurements of winds and waves. The system operates with two sets of antennas, one rotating and one looking to the side of the airplane. The rotating antennas yield neutral wind vectors at a height of 10 m above the ocean surface using a scatterometer model function to relate measured cross sections to wind speed and direction. The side-looking antennas produce maps of normalized radar cross section and line-of-sight velocity from which directional ocean wave spectra may be obtained. Capabilities of CORAR for wind and wave measurement are illustrated using data taken during the Shoaling Waves Experiment (SHOWEX) sponsored by the Office of Naval Research. Wind vectors measured by CORAR agree well with those measured by nearby buoys. Directional wave spectra obtained by CORAR also agree with buoy measurements and illustrate that offshore winds can produce dominant waves at an angle to the wind vector that are in good agreement with the measurements. The best agreement is produced using the Joint North Sea Wave Project (JONSWAP) parameterizations of the development of wave height and period with fetch.

Field experiments on wave-ice interaction in the Bering Sea and Greenland waters, 1979

Polar Record ◽  
1980 ◽  
Vol 20 (125) ◽  
pp. 147-153 ◽  
Author(s):  
Peter Wadhams ◽  
Vernon A. Squire
Keyword(s):  
Bering Sea ◽  
Field Experiments ◽  
Ground Truth ◽  
Ocean Waves ◽  
The Arctic ◽  
Naval Research ◽  
Washington Dc ◽  
East Greenland ◽  
Office Of Naval Research ◽  
The Bering Sea

Three field experiments in widely separated parts of the Arctic were carried out during 1979 to complete a study of the interaction between ocean waves and sea ice in the marginal ice zone. The aim of the project is to determine the distribution of floe sizes that is generated by a given incident wave field, and this requires measurements of wave decay, of the bending and body responses of floes, and of the strain necessary to cause fracture. The first series of experiments was carried out in 1978 (Wadhams, 1979) off Labrador and east Greenland. The 1979 series consisted of participation in a University of Washington cruise aboard the National Oceanic and Atmospheric Administration (NOAA) ship Surveyor to the Bering Sea; participation in the ground truth component of the Sursat remote sensing experiment off west Greenland; and finally a main summer experiment at Mesters Vig, east Greenland, in the same location as the 1978 main experiment. The Office of Naval Research (ONR), Washington DC, funded the study, and the two Greenland experiments were carried out in cooperation with the Electromagnetics Institute, Technical University of Denmark (TUD), Lyngby, with Danish government finance.

scholarly journals Towards a three-dimensional model of wave–ice interaction in the marginal ice zone

2010 ◽  
Vol 662 ◽  
pp. 1-4 ◽  
Author(s):  
C. M. LINTON
Keyword(s):  
Three Dimensional ◽  
Ocean Waves ◽  
Wave Spectra ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Past ◽  
Marginal Ice Zone ◽  
Directional Wave ◽  
Ice Floes ◽  
Made In

Over the past forty or so years, considerable advances have been made in our understanding of the effects of ocean waves on sea ice, and vice versa, with observations, experiments and theory all playing their part. Recent years have seen the development of ever more sophisticated mathematical models designed to represent the physics more accurately and incorporate new features. What is lacking is an approach to three-dimensional scattering for ice floes that is both accurate and efficient enough to be used as a component in a theory designed to model the passage of directional wave spectra through the marginal ice zone. Bennetts & Williams (J. Fluid Mech., 2010, this issue, vol. 662, pp. 5–35) have brought together a number of solution techniques honed on simpler problems to provide just such a component.

Radar Measurement of Ocean Waves

2011 ◽  
Author(s):  
W. Rob Story ◽  
Thomas C. Fu ◽  
Erin E. Hackett
Keyword(s):  
Ocean Waves ◽  
Lessons Learned ◽  
Sea Surface ◽  
Naval Research ◽  
Sea Clutter ◽  
Analysis Techniques ◽  
Radar Images ◽  
Sea Surface Topography ◽  
Radar Systems ◽  
Wave Radar

Over the past two decades a number of advances have been made in the use of radar systems for the measurement of ocean waves, building on early work at universities and the Naval Research Lab (NRL) to investigate the potential for extracting wave field measurements from the sea clutter seen in shipboard radar images. This early work was the foundation for modern wave radar systems, with hardware systems ranging from commercial off the shelf (COTS) incoherent navigation radar to specially developed, calibrated, coherent instrumentation radar and phased-array systems. Software algorithms and image analysis techniques have also been in constant development, which have evolved from 2D analysis of digitized images into modern techniques performing real-time 3D transformation of high resolution images. Most of these systems are being utilized to measure the directional wave spectra, with some systems also providing wave height estimates and sea surface elevation maps. More recently, the Naval Surface Warfare Center, Carderock Division (NSWCCD) and others have begun to utilize these techniques for shipboard measurement of open ocean waves. All these efforts have led to higher fidelity data, as well as data that were previously unobtainable. In this paper we provide an overview and history of the development of COTS incoherent wave radar systems, analysis techniques, and capabilities, from early characterization of sea clutter return to the latest developments in image inversion and sea surface topography. This review and summary provides a foundation on which to develop analysis techniques for the higher fidelity data, using lessons learned to improve future analysis. While not intending to be exhaustive, this paper seeks to highlight the insights gained from both historical and recent applications of these techniques, as well as the difficulties and issues associated with shipboard measurements such as ship motion, logistical constraints, and environmental factors.

Field experiments on wave-ice interaction in the Labrador and east Greenland currents, 1978

Polar Record ◽  
1979 ◽  
Vol 19 (121) ◽  
pp. 373-376 ◽  
Author(s):  
Peter Wadhams
Keyword(s):  
Field Experiments ◽  
Wave Attenuation ◽  
Ocean Waves ◽  
Naval Research ◽  
Washington Dc ◽  
Ice Dynamics ◽  
East Greenland ◽  
Office Of Naval Research ◽  
Pack Ice ◽  
Polar Research Institute

Two field experiments took place in 1978 as part of a project to study ocean wave attenuation in the marginal pack ice zone and the effect of ocean waves on floe break-up and ice dynamics. The main partners in the project are the Scott Polar Research Institute and the Electromagnetics Institute, Technical University of Denmark (TUD), Lyngby, with funding from the Office of Naval Research (ONR), Washington DC, and the Danish government. The first experiment was a pilot study carried out in co-operation with C-CORE (Centre for Cold Oceans Resources Engineering) at Memorial University of Newfoundland, St John's, and took place in the Labrador Sea. The second experiment was a major field study carried out in September 1978 from Mesters Vig, east Greenland. The project will be completed by a second main experiment at Mesters Vig in summer 1979, with supporting experiments in the Bering Sea and west Greenland in spring 1979.

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