On the Doppler Frequency Shifts of Radar Signals Backscattered from the Sea Surface

Ермаков, С. А.; Kapustin, Ivan A.; Kudryavtsev, V. N.; Sergievskaya, Irina; Shomina, Olga V.; Chapron, Bertrand; Yurovskiy, Yu. Yu.

doi:10.1007/s11141-014-9507-8

Cited by 18 publications

(12 citation statements)

References 23 publications

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“…Early K a -band measurements have been collected during NORDSEE platform experiments [6], [7]. Impact of waves on radar backscattering modulation is normally described in terms of a complex Modulation Transfer Function (MTF) [8], which experimental estimates are available from tower-based and air/space-borne sensors [6], [7], [9]- [13]. Theoretical explanation of observed MTF is generally based on the relaxation approximation for Bragg waves [14].…”

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confidence: 99%

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Modulation of Ka-Band Doppler Radar Signals Backscattered From the Sea Surface

Yurovsky

Kudryavtsev

Chapron

et al. 2018

IEEE Trans. Geosci. Remote Sensing

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confidence: 99%

“…11for hydro-MTF (dash-dotted lines), Bragg spectral MTF (dashed blue lines), and NP MTF (solid red lines). Green lines are theoretical hydro-MTF(13). Empirical estimates of whitecap MTF from[32] (closed circles) and[38] (open circles).…”

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confidence: 99%

Modulation of Ka-Band Doppler Radar Signals Backscattered From the Sea Surface

Yurovsky

Kudryavtsev

Chapron

et al. 2018

IEEE Trans. Geosci. Remote Sensing

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“…The problem of scattering of microwaves on the rough surface in application to radar remote sensing of the ocean has been actively discussed in the literature for some decades (see, for example, [1][2][3][4][5][6][7] and references therein). Some recent studies are focused on the role of wind wave breaking in the formation of radar return [8][9][10][11][12][13]. It is supposed nowadays that multipolarization radar observations can improve our understanding of the physical processes responsible for radar backscattering and to extend our capabilities in the characterization of marine currents, internal waves, slicks and so…”

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confidence: 99%

Modulation of Dual-Polarized X-Band Radar Backscatter Due to Long Wind Waves

et al. 2019

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Investigation of microwave scattering mechanisms is extremely important for developing methods for ocean remote sensing. Recent studies have shown that a common two-scale scattering model accounting for resonance (Bragg) scattering has some drawbacks, in particular it often overestimates the vertical-to-horizontal polarization radar return ratio and underestimates the radar Doppler shifts if the latter are assumed as associated with quasi linear resonance surface waves. It is supposed nowadays that radar backscattering at moderate incidence angles is determined not only by resonance Bragg mechanism but also contains non polarized (non Bragg) component which is associated supposedly with wave breaking but which is still insufficiently studied. Better understanding of the scattering mechanisms can be achieved when studying variations of radar return due to long wind waves. In this paper, results of experiments from an Oceanographic Platform on the Black Sea using dual co-polarized X-band scatterometers working at moderate incidence are presented and variations of Bragg and non-Bragg components (BC and NBC, respectively) and radar Doppler shifts are analysed. It is established that BC and NBC are non-uniformly distributed over profile of dominant (decametre-scale) wind waves (DWW). Variations of BC are characterized by some “background” return weakly modulated with the dominant wind wave periods, while NBC is determined mostly by rare and strong spikes occurred near the crests of the most intense individual waves in groups of DWW. We hypothesize that the spikes are due to intensification of nonlinear structures on the profile of short, decimetre-scale wind waves when the latter are amplified by intense DWW. Bragg scattering in slicks under the experimental conditions was suppressed stronger than NBC and spikes dominated in total radar return. It is obtained that radar Doppler shifts at HH-polarization are larger than at VV-polarization, particularly in slicks, the same relation is for NBC and BC Doppler shifts, thus indicating different scattering mechanisms for these components.

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“…The methods of extracting the period and direction of the waves from the radar data are well-developed [Young et al, 1985]. However, the estimation of the wave spectrum is difficult due to the complex physical features of the modulation transfer function [Ermakov et al, 2014]. The possibility of measuring the wave height based on the data on the backscattering intensity has been studied in a number of papers, e.g., in [Dankert et al, 2005].…”

Section: Introductionmentioning

confidence: 99%

Estimation of the wind-driven wave spectrum using a high spatial resolution coherent radar

Ermoshkin¹,

Kapustin²

2019

Russ. J. Earth Sci.

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The paper deals with experimental determination of the wind-driven wave spectrum by using the remote method of high-resolution coherent radar sensing of the water surface. The method is applied to the conditions of the fetch-limited wind wave growth, which is typical for enclosed waters and the sea nearshore, where the dominant wavelength is of the order of ten meters. The experiments were performed using a coherent X-band panoramic digital radar operating with the horizontal polarization for transmission and reception. The paper considers an algorithm used to form velocity images of the water surface from the data of coherent radar sensing on the basis of the phase angle difference method. The paper shows the possibility to recover wind wave spectra from the data on the Doppler shift of microwave radio waves. A theoretical justification and an experimental verification of the method are provided. Appearance of the third harmonic of the wind waves recovered from the radar sensing data of the spatio-temporal spectra of Doppler velocities is demonstrated for the first time. The functions that relate to the wave elevation spectra and the Doppler velocity spectra are determined. It is shown that the linear free-surface wave approximation is valid for the reconstruction of wave spectra. The temporal and spatial omnidirectional wave spectra obtained in the experiment are described well by the power model functions using the exponent factor of −4 and −5/2, respectively. The presented results may be used for studies of interaction between the harmonics of wind waves with the bottom topography, wave-current interaction, diagnostic of non-homogeneous currents, and other hydrophysical processes. KEYWORDS: Coherent radar; Doppler velocity; wind wave spectra.Citation: Ermoshkin, A. V. and I. A. Kapustin (2019), Estimation of the wind-driven wave spectrum using a high spatial resolution coherent radar, Russ.

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On the Doppler Frequency Shifts of Radar Signals Backscattered from the Sea Surface

Cited by 18 publications

References 23 publications

Modulation of Ka-Band Doppler Radar Signals Backscattered From the Sea Surface

Modulation of Ka-Band Doppler Radar Signals Backscattered From the Sea Surface

Modulation of Dual-Polarized X-Band Radar Backscatter Due to Long Wind Waves

Estimation of the wind-driven wave spectrum using a high spatial resolution coherent radar

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