scholarly journals Shallow Bathymetry from Multiple Sentinel 2 Images via the Joint Estimation of Wave Celerity and Wavelength

2021 ◽  
Vol 13 (11) ◽  
pp. 2149
Author(s):  
Marcello de Michele ◽  
Daniel Raucoules ◽  
Deborah Idier ◽  
Farid Smai ◽  
Michael Foumelis
Keyword(s):  
Dispersion Relation ◽  
Water Depth ◽  
Time Lag ◽  
Ocean Waves ◽  
Joint Estimation ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
Wave Celerity ◽  
Resolution Cell ◽  
Sentinel 2

In this study, we present a new method called BathySent to retrieve shallow bathymetry from space that is based on the joint measurement of ocean wave celerity (c) and wavelength (λ). We developed the method to work with Sentinel 2 data, exploiting the time lag between two Sentinel 2 spectral bands, acquired quasi-simultaneously, from a single satellite dataset. Our method was based on the linear dispersion law, which related water depth to wave celerity and wavelength: when the water depth was less than about half the dominant wavelength, the wave celerity and wavelength decreased due to decreasing water depth (h) as the waves propagated towards the coast. Instead of using a best weighted (c,λ) fit with the linear dispersion relation to retrieve h, we proposed solving the linear dispersion relation for each (c,λ) pair to find multiple h-values within the same resolution cell. Then, we calculated the weighted averaged h-value for each resolution cell. To improve the precision of the final bathymetric map, we stacked the bathymetry values from N-different datasets acquired from the same study area on different dates. We first tested the algorithm on a set of images representing simulated ocean waves, then we applied it to a real set of Sentinel 2 data obtained of our study area, Gâvres peninsula (France, 47°,67 lat.; −3°35 lon.). A comparison with in situ bathymetry yielded good results from the synthetic images (r2 = 0.9) and promising results with the Sentinel 2 images (r2 = 0.7) in the 0–16 m depth zone.

Linear dispersion relation for a fluid of light in an atomic vapor

2017 ◽  
Author(s):  
Quentin Fontaine ◽  
Agostino Apra ◽  
Giovanni Lerario ◽  
Elisabeth Giacobino ◽  
Alberto Bramati ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Atomic Vapor ◽  
Linear Dispersion ◽  
Linear Dispersion Relation

scholarly journals Dispersive magnetized waves in the solar wind plasma

2010 ◽  
Vol 77 (3) ◽  
pp. 357-365 ◽  
Author(s):  
B. DASGUPTA ◽  
DASTGEER SHAIKH ◽  
P. K. SHUKLA
Keyword(s):  
Solar Wind ◽  
Dispersion Relation ◽  
Fluid Model ◽  
Phase Speed ◽  
Solar Wind Plasma ◽  
Small Scale ◽  
Linear Dispersion ◽  
Length Scales ◽  
Linear Dispersion Relation ◽  
Two Fluid Model

AbstractWe derive a generalized linear dispersion relation of waves in a strongly magnetized, compressible, homogeneous and isotropic quasi-neutral plasma. Starting from a two-fluid model, describing distinguishable electron and ion fluids, we obtain a six-order linear dispersion relation of magnetized waves that contains effects due to electron and ion inertia, finite plasma beta and angular dependence of phase speed. We investigate propagation characteristics of these magnetized waves in a regime where scale lengths are comparable with electron and ion inertial length scales. This regime corresponds essentially to the solar wind plasma, where length scales, comparable with ion cyclotron frequency, lead to dispersive effects. These scales in conjunction with linear waves present a great deal of challenges in understanding the high-frequency, small-scale dynamics of turbulent fluctuations in the solar wind plasma.

scholarly journals Measurement of the dispersion relation for random surface gravity waves

2015 ◽  
Vol 766 ◽  
pp. 326-336 ◽  
Author(s):  
Tore Magnus A. Taklo ◽  
Karsten Trulsen ◽  
Odin Gramstad ◽  
Harald E. Krogstad ◽  
Atle Jensen
Keyword(s):  
Dispersion Relation ◽  
Gravity Waves ◽  
Laboratory Experiments ◽  
Surface Gravity ◽  
Linear Dispersion ◽  
Random Surface ◽  
Zakharov Equation ◽  
Surface Gravity Waves ◽  
Linear Dispersion Relation ◽  
Jonswap Spectrum

AbstractWe report laboratory experiments and numerical simulations of the Zakharov equation, designed to have sufficient resolution in space and time to measure the dispersion relation for random surface gravity waves. The experiments and simulations are carried out for a JONSWAP spectrum and Gaussian spectra of various bandwidths on deep water. It is found that the measured dispersion relation deviates from the linear dispersion relation above the spectral peak when the bandwidth is sufficiently narrow.

Terahertz planar waveguide devices based on graphene

2017 ◽  
Vol 31 (05) ◽  
pp. 1750045
Author(s):  
Yizhe Yuan ◽  
Xiaoyong Guo ◽  
Liqun An ◽  
Wen Xu
Keyword(s):  
Dispersion Relation ◽  
Planar Waveguide ◽  
Theoretical Study ◽  
Transmission Characteristics ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
Planar Structures ◽  
Waveguide Devices

We present a theoretical study on graphene-semiconductor planar structures. The frequency of the photonic modes in the structure, which can be efficiently tuned via varying the sample parameters, is within the terahertz (THz) bandwidth. Furthermore, it is found that a roughly linear dispersion relation can be obtained for photonic modes in the THz region. Hence, the proposed graphene-semiconductor planar structures can be served as THz waveguide with desirable transmission characteristics.

The Growth of Localized Disturbances in Unstable Flows

1982 ◽  
Vol 49 (2) ◽  
pp. 284-290 ◽  
Author(s):  
A. D. D. Craik
Keyword(s):  
Dispersion Relation ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Computational Effort ◽  
Plane Poiseuille Flow ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
Practical Possibility ◽  
Proposed Model ◽  
Axis Of Symmetry

The development of three-dimensional localized disturbances in unstable flows was recently studied by Craik [1] using a model dispersion relation. The adoption of such an approximate formula for the linear dispersion relation allows a dramatic reduction in computational effort, in comparison with more precise calculations (e.g., Gaster [3], [5]), yet may still yield quite accurate results. Craik [1] gives simple analytical solutions for various limiting cases of his chosen model. Here, this model is further investigated. Numerical results are given which are free of previous scaling assumptions and the accuracy of the proposed model is assessed by comparison with known exact computations for plane Poiseuille flow. Certain improvements are made by including further terms in the model dispersion relation and the influence of these additional terms is determined. A further model is investigated which yields “splitting” of the wave packet into two regions of greatest amplitude, one on either side of the axis of symmetry. Such behavior may be characteristic of many flows at sufficiently large Reynolds numbers. Extension of this work to three-dimensional and slowly varying flows seems a practical possibility.

scholarly journals Interpretation of dispersion relations for bounded systems

1972 ◽  
Vol 7 (1) ◽  
pp. 13-48 ◽  
Author(s):  
T. D. Rognlien ◽  
S. A. Self
Keyword(s):  
Dispersion Relation ◽  
Boundary Conditions ◽  
Normal Modes ◽  
Plasma Waves ◽  
Axial Current ◽  
Linear Dispersion ◽  
Linear Dispersion Relation ◽  
End Plate ◽  
Cylindrical Form ◽  
Bounded System

A treatment is given of the problem of constructing normal modes for anarbitrarily bounded system from roots of the linear dispersion relationD( ω, k) = 0 for the corresponding infinite or periodically bounded system. For a system described by continuous macroscopic variables, and of general cylindrical form (uniform along an axisz, say), each transverse eigenmode gives rise to a set of axial normal modes constructed from a pair of dominant rootskαz(ω) ofD= 0 satisfying the boundary conditions which are characterized by complex reflexion coefficients for the dominant waves. The implications of the results for the interpretation of experiments on plasma waves and instabilities on finite cylinders are discussed, with particular reference to the effects of end-plate damping and axial current onQ-machines.

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