Directional spreading function of the sea wave spectrum at short scale, inferred from multifrequency radar observations

1996 ◽  
Vol 101 (C7) ◽  
pp. 16601-16613 ◽  
Author(s):  
G. Caudal ◽  
D. Hauser
Keyword(s):  
Wave Spectrum ◽  
Radar Observations ◽  
Short Scale ◽  
Spreading Function ◽  
Multifrequency Radar ◽  
Sea Wave

scholarly journals Directional Spreading Function of the Gravity-Capillary Wave Spectrum Derived from Radar Observations

2017 ◽  
Vol 9 (4) ◽  
pp. 361 ◽  
Author(s):  
Xuan Zhou ◽  
Jinsong Chong ◽  
Haibo Bi ◽  
Xiangzhen Yu ◽  
Yingni Shi ◽  
...  
Keyword(s):  
Capillary Wave ◽  
Wave Spectrum ◽  
Radar Observations ◽  
Spreading Function

A Generic Method to Model Frequency-Direction Wave Spectra for FPSO Motions

2008 ◽  
Author(s):  
Hermione J. van Zutphen ◽  
Philip Jonathan ◽  
Kevin C. Ewans
Keyword(s):  
Frequency Spectrum ◽  
Two Dimensions ◽  
Wind Forcing ◽  
Wave Spectra ◽  
Spectral Form ◽  
New Approach ◽  
Spreading Function ◽  
Wind Sea ◽  
Model Frequency ◽  
Sea Wave

We report a new approach to model the frequency-direction spectrum, in which the frequency-direction spectra from measurements or hindcast studies are fitted simultaneously in two dimensions, frequency and direction. Depending on the amount of wind forcing on the partition, either a unimodal (swell) or bimodal (wind-sea) wave spreading function is adopted together with the spectral form which best fits the frequency spectrum. This paper describes the new method and presents the results on a measured dataset.

Investigation of short-scale sea wave spectra with optical and radiometric methods

2019 ◽  
Author(s):  
Victor I. Titov ◽  
Victor Bakhanov ◽  
A. A. Demakova ◽  
Irina A. Sergievskaya ◽  
Aleksey Kuzmin ◽  
...  
Keyword(s):  
Wave Spectra ◽  
Short Scale ◽  
Sea Wave

scholarly journals Absolute Calibration of Radar Altimeters: Consistency with Electromagnetic Modeling

2005 ◽  
Vol 22 (6) ◽  
pp. 771-781 ◽  
Author(s):  
Gérard Caudal ◽  
Emmanuel Dinnat ◽  
Jacqueline Boutin
Keyword(s):  
Wind Speed ◽  
Empirical Model ◽  
Wave Spectrum ◽  
Absolute Calibration ◽  
Electromagnetic Modeling ◽  
Model Function ◽  
Electromagnetic Model ◽  
Using Data ◽  
Sea Wave

Abstract Empirical Ku-band altimeter model functions of near-nadir normalized radar cross-sectional σ° are compared to electromagnetic two-scale quasi-specular theory in the context of a standard sea wave spectral model. Three empirical model functions are tested: (i) the modified Chelton and Wentz model (WCM) using data from Geosat, (ii) the Callahan et al. model using data from TOPEX, and (iii) the Freilich and Vanhoff model using data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR). These three models are basically very similar, except that they differ in terms of the level of absolute calibration. The difference between the absolute calibrations of the two extreme models (MCW and Freilich and Vanhoff) is as high as 1.9 dB. Assuming a sea wave spectrum similar to that used by Elfouhaily et al., the two-scale quasi-specular electromagnetic model is run, with a wave separation wavenumber kd adjusted so as to minimize the rms difference between the theoretical σ°(θ) function and the empirical near-nadir model function. The quality of the best-fit solution is not perfect, however, because the shape and absolute level of the function σ°(θ) cannot usually be adjusted simultaneously by the electromagnetic model. Taking the model function used by Freilich and Vanhoff as a reference, an offset is then introduced to the empirical model function, and the residual error is computed as a function of the offset. The overall quality of the fit is shown to be best when a −1.1 dB offset is introduced into the Freilich and Vanhoff model function. To within 0.1 dB, this corresponds to the offset that would be required to match Callahan et al.’s model function. This result is obtained in a context where the effect of the peakedness of the sea surface was assumed negligible. When this effect is introduced, with a peakedness parameter Δ assumed to be independent of wind speed and taken tentatively as Δ = 0.23, as suggested by Chapron et al., the optimal offset is then found to be −0.2 dB, thus indicating that for this example the best consistency with electromagnetic modeling is closer to Freilich and Vanhoff’s calibration. A more refined assessment would require accurate measurements of the parameter Δ involving both magnitude and variability with wind speed. Such accurate measurements are, unfortunately, not available at this time.

scholarly journals Numerical Modeling of Wave Disturbances in the Process of Ship Movement Control

Algorithms ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 130 ◽  
Author(s):  
Piotr Borkowski
Keyword(s):  
Stochastic Process ◽  
Numerical Modeling ◽  
Numerical Model ◽  
Wave Spectrum ◽  
Movement Control ◽  
Angular Speed ◽  
Stabilization System ◽  
Wave Impact ◽  
Wave Disturbances ◽  
Sea Wave

The article presents a numerical model of sea wave generation as an implementation of the stochastic process with a spectrum of wave angular velocity. Based on the wave spectrum, a forming filter is determined, and its input is fed with white noise. The resulting signal added to the angular speed of a ship represents disturbances acting on the ship’s hull as a result of wave impact. The model was used for simulation tests of the influence of disturbances on the course stabilization system of the ship.

scholarly journals Impact of Mass–Size Parameterizations of Frozen Hydrometeors on Microphysical Retrievals: Evaluation by Matching Radar to In Situ Observations from GCPEx and OLYMPEx

2020 ◽  
Vol 37 (6) ◽  
pp. 993-1012 ◽  
Author(s):  
Ousmane O. Sy ◽  
Simone Tanelli ◽  
Stephen L. Durden ◽  
Andrew Heymsfield ◽  
Aaron Bansemer ◽  
...  
Keyword(s):  
Cold Season ◽  
Radar Observations ◽  
Microphysical Properties ◽  
Precipitation Experiment ◽  
Mass Size ◽  
Ice Water Content ◽  
Multifrequency Radar ◽  
Ice Water ◽  
In Situ Scattering

AbstractThis article illustrates how multifrequency radar observations can refine the mass–size parameterization of frozen hydrometeors in scattering models and improve the correlation between the radar observations and in situ measurements of microphysical properties of ice and snow. The data presented in this article were collected during the GPM Cold Season Precipitation Experiment (GCPEx) (2012) and Olympic Mountain Experiment (OLYMPEx) (2015) field campaigns, where the true mass–size relationship was not measured. Starting from size and shape distributions of ice particles measured in situ, scattering models are used to simulate an ensemble of reflectivity factors for various assumed mass–size parameterizations (MSP) of the power-law type. This ensemble is then collocated to airborne and ground-based radar observations, and the MSPs are refined by retaining only those that reproduce the radar observations to a prescribed level of accuracy. A versatile “retrieval dashboard” is built to jointly analyze the optimal MSPs and associated retrievals. The analysis shows that the optimality of an MSP depends on the physical assumptions made in the scattering simulators. This work confirms also the existence of a relationship between parameters of the optimal MSPs. Through the MSP optimization, the retrievals of ice water content M and mean diameter Dm seem robust to the change in meteorological regime (between GCPEx and OLYMPEx); whereas the retrieval of the diameter spread Sm seems more campaign dependent.

scholarly journals Imbalance of energy and momentum source terms of the sea wave transfer equation for fully developed seas

Ocean Science ◽  
2012 ◽  
Vol 8 (6) ◽  
pp. 1085-1098
Author(s):  
G. V. Caudal
Keyword(s):  
Wave Breaking ◽  
Transfer Equation ◽  
Wave Spectrum ◽  
Momentum Balance ◽  
Spectral Energy ◽  
Source Terms ◽  
Spectral Flux ◽  
Energy And Momentum ◽  
Wind Source ◽  
Sea Wave

Abstract. In the concept of full development, the sea wave spectrum is regarded as a nearly stationary solution of the wave transfer equation, where source and sink terms should be in balance with respect to both energy and momentum. Using a two-dimensional empirical sea wave spectral model at full development, this paper performs an assessment of the compatibility of the energy and momentum budgets of sea waves over the whole spectral range. Among the various combinations of model functions for wave breaking and wind source terms tested, not one is found to fulfill simultaneously the energy and momentum balance of the transfer equation. Based on experimental and theoretical grounds, wave breaking is known to contribute to frequency downshift of a narrow-banded wave spectrum when the modulational instability is combined with wave breaking. On those grounds, it is assumed that, in addition to dissipation, wave breaking produces a spectral energy flux directed toward low wavenumbers. I show that it is then possible to remove the energy and momentum budget inconsistency, and correspondingly the required strength of this spectral flux is estimated. Introducing such a downward spectral flux permits fulfilling both energy and momentum balance conditions. Meanwhile, the consistency between the transfer equation and empirical spectra, estimated by means of a cost function K, is either improved or slightly reduced, depending upon the wave breaking and wind source terms chosen. Other tests are performed in which it is further assumed that wave breaking would also be associated with azimuthal diffusion of the spectral energy. This would correspondingly reduce the required downward spectral flux by a factor of up to 5, although it would not be able to remove it entirely.

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