It is well known that wave dispersion in inhomogeneous media leads to energy flux weakening on large distances. The more interesting cases are when inhomogeneity does not prevent wave propagation. This problem is studied here for internal waves in the ocean. Firstly, the penetration of internal waves into a deep ocean, stratified with density and current, is discussed, and it is shown that there is sufficient number of stratification profiles allowing non-reflected wave propagation into the ocean bulk. Further the internal wave propagation in two-layer stratified ocean of variable depth is investigated. The set of bottom profiles where the wave energy is not scattered, is also found.

Precise numerical model of potential; surface waves is used to investigate the wave field evolution, initially assigned as a train of harmonic waves. It is shown that harmonic wave of any amplitude quickly generates the new modes, which undergo the complicated evolution. These modes can be referred neither to bound waves nor to free waves.

An operational system for forecasting of hydrodynamic characteristics in the Gulf of Finland GULFOOS (the Gulf of Finland Operational Oceanographic System) has been developed. The system is based on the hydrodynamic module of St. Petersburg Baltic Eutrophication Model. The system has been working in the operation mode from May 2009 using data from short-term weather forecasts for the North-West Region of Russia and forecasts of boundary conditions at the entrance in the Gulf of Finland. 48-hour model forecasts were compared to observed vertical temperature and salinity profiles and water level in Kronshtadt. The comparison showed that the model system simulates the observations quite well.

Applications of large-eddy simulation (LES) technique to the solution of problems of hydrophysics and hydroacoustics are considered. Solutions of some model problems (free mixing layer, free sub-sonic nonisothermal turbulent jet flowing out of circular nozzle into submerged space, and aero-optical effects in turbulent flows) are presented. The results obtained are compared to the data calculated with the numerical solution of the Reynolds-averaged Navier–Stokes equations and equations of the k–ε turbulence model, as well as to the available experimental data. The conclusions related to the perspectives of use of this technique in the problems of hydrophysics and hydroacoustics are made.

The paper contains a brief review of aperture synthesis techniques for towed arrays operating in passive mode. A technique is suggested that is able to process wideband signals, also from multiple sources (as opposed to known techniques). The results of experimental studies of aperture synthesis are presented, obtained both from computer-generated signals (SynApp program has been developed for this purpose), and from signals of a real underwater towed array.

The authors consider some problems of supporting Russia sea activity in the important water areas of the World ocean, which cause creation of geoacoustic databases and the geoacoustic models of a sea-bottom required for all carriers of sonar means of underwater conditions imaging for operative forecasting of surveillance conditions in the navigation area and supporting efficient operation of adaptive hydroacoustic information processing algorithms. The concept of common water areas sea-bottom database creation and sea bottom geoacoustic modeling techniques are offered. Data about structure of a perspective integrated sonar system of sea-bottom monitoring and problems solved with its help are cited.

We develop algorithms for retrieval of the water layer modulation transfer function (MTF) from the radiance of backscattered laser pulse. A lidar diagram is developed for remote measuring of the MTF. The water optical properties are then retrieved from measured MTF. We also propose a laser imaging system for sea bottom observation which corrects image distortion caused by light scattering in the water.