Peculiarities of the Acoustic Pulse Formation Reflected by the Water Surface: a Numerical Experiments and the Results of Long-term Measurements Using the "Kalmar" Sonar

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.