A Review of Wave Spectrum Models as Applied to the Problem of Radar Probing of the Sea Surface

Abstract

The most common models of the wind wave spectrum are reviewed, and the compliance of the studied spectra with several fundamental criteria is estimated. These criteria are the ability to simulate diverse wave climate and agreement between model‐based calculations of the mean square slope and experimental data. The spreading function of the spectrum should also correspond to the experimentally measured Doppler spectrum, while the dependence of the radar backscatter cross section should conform to geophysical model functions for various wavelength ranges of incident electromagnetic radiation at moderate incidence angles (20–60°). An analysis has shown that none of the considered spectrum models fully satisfies all the criteria; thus, a new spectrum model for wind waves was developed. Boundary wave numbers for various wavelength ranges of incident electromagnetic radiation within the framework of a two‐scale surface model were determined for the new model. The spectrum model can be used to simulate ripple attenuation in oil slicks and to calculate the radar backscatter cross section inside slick.

On Modeling of Quad‐Polarization Radar Scattering From the Ocean Surface With Breaking Waves

“…Journal of Geophysical Research: Oceans Ryabkova et al (2019). A previous study has reported that CB model-simulated HH-and VV-pol radar backscatters are close to spaceborne C-band SAR observations, while VH-pol simulations are found to be significant underestimates .…”

“…Accordingly, the radar backscatter cross section per unit area of the ocean surface is as follows: where p ( tanψ , tanδ ) is the joint probability density of slopes for the large‐scale roughness of the ocean surface. In our study, in addition to tilt modulation, we also consider the effect of hydrodynamic modulation, which is implemented by multiplying the spectrum W ( k , ϕ ) by the hydrodynamic modulation coefficient f ( q x , ϕ ) from Ryabkova et al (2019). A previous study has reported that CB model‐simulated HH‐ and VV‐pol radar backscatters are close to spaceborne C‐band SAR observations, while VH‐pol simulations are found to be significant underestimates (Hwang et al, 2010).…”

“…In addition to the empirical spectral models mentioned above, a physical model (K-spec) was developed for description of short wind waves with length scales between a few millimeters to a few meters, by solving the energy spectral density balance equation (Kudryavtsev et al, 1999). Moreover, the most common models of the wind wave spectrum models have been recently reviewed for radar remote sensing of ocean surface (Ryabkova et al, 2019). Although these spectra can be used for microwave backscatter and emission computations, for a specific EM scattering model, different spectral models may yield discrepant results even with the same radar configurations and wind conditions.…”

Wind Wave Effects on Remote Sensing of Sea Surface Currents From SAR

“…Journal of Geophysical Research: Oceans measurements than wind-generated gravity waves. The influence of applying different shortwave spectral models in construction of estimates for the radar backscatter cross section has been addressed extensively (e.g., Hwang & Plant, 2010;Ryabkova et al, 2019). We briefly examine their influence in the WASV estimates by applying another two widely used shortwave spectral models, one proposed by Elfouhaily et al (1997) In Figure 11a, we show the azimuthally distributed WASV as estimated with different spectral models.…”

Bistatic Doppler spectrum of radiation reflected by a water surface

“…Unique experiments on the reception of GLONASS signals reflected by the water surface, considering their features and advantages, were carried out at the offshore testing area in Sweden [Hobiger et al, 2014]. A significant step forward in this area was the launch in 2016 by the American space agency (NASA) of the CYGNSS mission [Ruf et al, 2016], consisting of 8 moving one after another small spacecraft equipped with GPS signal receivers, designed to study the parameters of surface waves in tropical cyclones. Since 2017, the system is fully operational, and the measurement results are publicly available.…”