Real and synthetic aperture radars have been used in recent years to image ocean surface waves. Though wavelike patterns are often discernible on radar images, it is still not fully understood how they relate the actual wave field. The present paper reviews extends current models imaging mechanism. Linear transfer functions that two‐dimensional field real (SLAR) calculated by using two‐scale model. It noted a description of process these can only be adequate for low moderate sea states....

This paper reviews basic synthetic aperture radar (SAR) theory of ocean wave imaging mechanisms, using both known work and recent experimental theoretical results from the Marine Remote Sensing (MARSEN) Experiment. Several viewpoints that have contributed to field are drawn together in a general analysis backscatter statistics moving sea surface. A common focus for different scattering models is provided by mean image impulse response function, which shown be identical (spatially varying)...

A simple theoretical model of the imaging mechanism underwater bottom topography in tidal channels by real and synthetic aperture radar (SAR) is presented. The attributed to surface effects induced current variations over topography. modulates short‐scale roughness, which turn gives rise changes reflectivity. topography‐current interaction described continuity equation, current‐short wave weak hydrodynamic theory relaxation time approximation. This contains only one free parameter, time. It...

A new theory is presented explaining why not only short surface ripples, but also longer ocean waves are damped by oil films floating on the sea surface. The wave attenuation viscoelastic attributed to Marangoni effect, which causes a strong resonance‐type damping in short‐gravity‐wave region, and nonlinear wave‐wave interaction, means of energy transferred from sink resonance region. film changes free boundary condition tangential direction thus strongly modifies flow pattern layer. As...

Criteria for discriminating between radar signatures of oil films and biogenic slicks visible on synthetic aperture (SAR) images the sea surface as dark patches are critically reviewed. We question often claimed high success rate spill detection algorithms using single-polarization SARs because SAR used to train these based usually subjective interpretation not validated by on-site inspections or multi-sensor measurements carried out from pollution surveillance planes. Furthermore, we doubt...

Results from the analyses of several spaceborne imaging radar‐C/X‐band synthetic aperture radar (SIR‐C/X‐SAR) images are presented, which were acquired during two SIR‐C/X‐SAR missions in April and October 1994 by L‐, C‐, X‐band multipolarization SAR aboard space shuttle Endeavour. The showing natural (biogenic) surface slicks as well man‐made (anthropogenic) mineral oil spills analyzed with aim to study whether or not active techniques can be applied discriminating between these kinds films....

The formation of wave-like patterns in synthetic aperture radar (SAR) images the ocean surface caused by orbital motions is investigated. Furthermore, degradation azimuthal resolution due to these calculated applying a least square fit phase history. Formulas are given which describe variation intensity direction image plane as well function wave amplitude, frequency, propagation, and wavelength, incidence angle, integration time.

An improved composite surface model for the calculation of normalized radar backscattering cross section (NRCS) ocean at moderate incidence angles is presented. The based on Bragg scattering theory. A Taylor expansion NRCS in two‐dimensional slope yields nonzero second‐order terms which represent a first approximation effect geometric and hydrodynamic modulation facets by all waves that are long compared to these facets. corresponding expectation value varies with wave height spectral...

Two synthetic aperture radar (SAR) images acquired by the European Remote Sensing Satellite ERS‐1 over Jade‐Weser estuary in German Bight of North Sea on January 2 and 20, 1992, are analyzed. The show sea surface manifestations atmospheric boundary layer rolls. This is inferred from orientation quasi‐periodic patterns which aligned approximately with wind direction, ratio wavelength to height layer, conditions encountered as measured quasi‐simultaneously radiosondes. rolls were generated a...

In the companion paper we have presented an improved composite surface model for calculation of normalized radar backscattering cross sections (NRCS) ocean surface. The proposed accounts impact full two‐dimensional wave spectrum on backscatter and was shown to reproduce measured absolute NRCS values a variety configurations wind speeds satisfactorily after some reasonable tuning input spectrum. This focuses modulation in presence spatially varying currents. First, sensitivity intensity...

A wide variety of oceanic and atmospheric phenomena are often observed in around the sunglint region on optical images sea surface. The appearance these depends strongly viewing geometry with areas surface that rougher (or smoother) than background appearing as either brighter or darker depending their position relative to specular point. To understand signature variations, this paper introduces concept a critical sensor angle, defined zenith angle at which different roughness variances...

Airborne radar backscattering experiments carried out recently by Singh et al. (1986) over sea surfaces covered with mineral oil films show that the cross section depression has a maximum as function of incidence angle. In this paper we al.'s measurements can be explained Marangoni effect if assumption is made spill contained surface active material “impurities.” The causes resonance‐type wave damping in short gravity region when viscoelastic film. Maximum was observed at frequencies around...

A weakly nonhydrostatic, two‐layer numerical model based on the Boussinesq equations is presented which capable of describing, among others, generation and propagation nonlinear dispersive internal waves in Strait Gibraltar. The depends one space coordinate only, but it retains several features a fully three‐dimensional by including realistic bottom profile, variable channel width, trapezoidal cross section. primitive include horizontal diffusion, friction, friction between two water layers....

Scylla and Charybdis are, in Greek mythology, two immortal irresistible monsters who beset the narrow waters separating Italian peninsula from Sicily. They give poetic expressions to exceptional oceanographic features encountered Strait of Messina. Recently, SEASAT satellite has added new information on oceanography this strait. For first time, experimental evidence is presented that internal waves are generated The generation mechanism linked tidal currents washing over shallow sill within...

A theoretical model previously developed for describing the imaging of monochromatic ocean waves by synthetic aperture radar (SAR) is extended to relate wave spectra SAR image spectra. Since response moving surface nonlinear a large range parameters, this relationship can, in general, not be described linear mapping transfer function. are calculated from given applying Monte Carlo simulation techniques. The computer simulations performed with varying parameters and unidirectional field...

Abstract The high wavenumber detection cut-off is determined above which the spectrum of ocean waves imaged by a synthetic aperture radar (SAR) lost in background noise consisting clutter associated with Rayleigh statistics backscattering surface and thermal originating SAR system itself. For given power, maximum attained if resolution chosen such that spectra are equal at wavenumber. Assuming constant modulation transfer function relating image wave slope spectra, this case proportional to...

Abstract The imaging of ocean surface waves by synthetic aperture radar (SAR) is investigated using two-dimensional Monte-Carlo simulations. properties the SAR mechanism for windseas and swell in Bragg scattering regime are discussed as a function few governing non-dimensional parameters formed from combination wave parameters. parameter ranges may be classified into three regimes corresponding to linear weakly nonlinear, medium nonlinear strongly imaging. nonlinearities induced motion...

It is well known that rain leaves footprints on the sea surface sometimes become visible synthetic aperture radar (SAR) images. Rain cells can easily be detected SAR images at all frequencies when they are associated with a downdraft pattern. But not always and also occur in other forms, as stratified rain, bands, squall lines. turns out signatures of C-band much more complex than L- or X-band it particularly difficult to identify unambiguously events acquired over ocean. This because lies...

A new numerical two-layer model is presented, which describes the generation of internal tidal bores and their disintegration into solitary waves in Strait Messina. This used to explain observations made by synthetic aperture radar (SAR) from European Remote Sensing satellites ERS 1 2. The analysis available 1/2 SAR data Messina adjacent sea areas show that 1) northward as well southward propagating are generated Messina, 2) observed more frequently than waves, 3) surface manifestations...

Radar signatures of rain cells are investigated using multifrequency/multipolarization synthetic aperture radar (SAR) images acquired from the space shuttle Endeavour during spaceborne imaging radar‐C/X‐band SAR (SIR‐C/X‐SAR) missions in April and October 1994. In SIR‐C/X‐SAR images, over ocean usually consist irregularly shaped bright dark patches that strongly depend on frequency polarization. The observed imagery originate (1) scattering attenuation microwaves by raindrops ice particles...

Radar signatures of mineral oil spills consisting heavy and light fuel were measured by an airborne five-frequency ( L - S C X K -band) multi u polarization microwave scatterometer flown on a helicopter during controlled spill experiment in the North Sea. The damping ratio, defined as ratio backscattered radar power from oil-free oil-covered sea surface, was at different frequencies incidence angles such that Bragg wavenumbers, k, between 20 radm 1 500 covered. B following results obtained:...