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.

The capabilities of a new instrument for measuring the surface wave parameters are studied in detail. An acoustic wave gauge with a single antenna is designed to measure the backscatter intensity and the Doppler spectrum of the reflected acoustic signal and to retrieve the variance of the vertical orbital velocity component. The new instrument is numerically simulated, and field experiments using a prototype acoustic wave gauge are carried out. The comparison of the variances of the vertical orbital velocity component measured by acoustic and string wave gauges under field conditions, as well as the comparison of measurements and numerical simulation results, has confirmed the high accuracy of the retrieval algorithms. The advantage of the instrument is its capability of making measurements in any water basin without the use of a fixed platform.

This work is devoted to the description of a new approach to measuring the parameters of sea waves using a pulsed sonar. Instead of analyzing the implementation of time to the biggest reflection, it is proposed to analyze the shape of the pulse reflected by the water surface. This approach is standard in space radar altimeters, where the significant wave height is determined by the shape of the leading edge of the reflected electromagnetic pulse. However, in hydroacoustics, this approach is proposed for the first time. The expressions obtained in previous works for calculating the shape of the reflected pulse are checked using numerical simulation of the experiment, as well as using a long-term experiment in the Black Sea using the "Kalmar" sonar. In this paper, a method is proposed for retrieving the significant wave height by the shape of the leading edge of a reflected pulse and the slope variance of the waves by the trailing edge of the reflected pulse. It should be noted that this slope variance of the waves is the same, which affects the scattering of electromagnetic signals in active radar when using the same radiation wavelength. This fact opens up new possibilities for using the proposed approach for sub-satellite measurements. The features of the formation and accumulation of the reflected pulse are considered based on formulas, numerical simulation, and experiment. The results of the new algorithm for retrieving the significant wave height and slope variance using experimental data are presented. The operation of the new algorithm is compared with the traditional estimate of the wave height by recording the implementation of time to the biggest reflection.

In the radar remote sensing of sea ice, the main informative parameter is the backscattering radar cross section (RCS), which does not always make it possible to unambiguously determine the kind of scattering surface (ice/sea waves) and therefore leads to errors in estimating the area of the ice cover. This paper provides a discussion of the possibility of using the Doppler spectrum of the reflected microwave signal to solve this problem. For the first time, a semi-empirical model of the Doppler spectrum of a radar microwave signal reflected by an ice cover was developed for a radar with a wide antenna beam mounted on a moving carrier at small incidence angles of electromagnetic waves (0°–19°). To describe the Doppler spectrum of the reflected microwave signal, the following parameters were used: shift and width of the Doppler spectrum, as well as skewness and kurtosis coefficients. Research was conducted on the influence of the main parameters of the measurement scheme (movement velocity, width of antenna beam, sounding direction, incidence angle) and the sea ice concentration (SIC) on the parameters of the Doppler spectrum. It was shown that, in order to determine the kind of scattering surface, it is necessary to use a wide or knife-like (by the incidence angle) antenna. Calculations confirmed the assumption that, when measured from a moving carrier, the Doppler spectrum is a reliable indicator of the transition from one kind of scattering surface to another. The advantage of using the coefficients of skewness and kurtosis in the analysis is that it is not necessary to keep the radar velocity unchanged during the measurement process.