The issue opens with a discussion of the problems associated with the description of the complicated motions of liquid media, which are accompanied by a multi-scale complex of non-equilibrium processes, including relaxation and inertial effects. The results of high-resolving modeling for the surface semidiurnal tide M2 in the Laptev Sea are discussed. They are obtained using a high-resolving version of 3D finite-element hydrostatic model QUODDY-4. The development of a software package IGWResearch2 is considered. This package contains numerical models, hydrological data, data preparation tools, analysis tools and observations’ information related to internal waves in the World Ocean. The results of the light attenuation coefficient measurements in the range of 400—800 nm in the waters of Lake Teletskoye obtained in a summer cruise (19—23 June 2018) are presented. The results of interferometric processing of the oceanographic large-scale experiment SWARM-95 on the coast of New Jersey are discussed. The results of calculation of the hydrodynamic interaction of the impeller, guide vanes and the pump-jet guide nozzle, obtained on the basis of numerical methods of viscous fluid dynamics, are presented. The paper describes a method for passively determining the distance to an underwater source using the curvature of the wave front of the source field in the Fresnel zone. A new (probabilistic) approach to the information processing algorithm of the magnetometer signal is proposed, which determines the width of the recommended search band of an object with guaranteed values of the probability characteristics of its detection. The bibliographic paper about one of the founders of inland hydrology Mikhail Andreyevich Velikanov is presented.
The results of optical studies of natural waters, including field measurements, remote sensing, and theoretical developments, are presented. The studies were performed in the Black and Azov Seas, Peter the Great Bay of the Sea of Japan, Lake Teletskoye, and the Gorky Reservoir. In the Black Sea, optical characteristics during periods of an intense coccolithophore bloom in 2012 and 2017 were studied, and the influence of suspended and dissolved organic matter on underwater irradiance and the efficiency of light absorption by phytoplankton pigments. In Peter the Great Bay, studies were performed to influence of the thickness and state of the ice surface on the irradiance under the ice cover, and the impact of internal waves on the optical characteristics of the sea surface. For the Sea of Azov, a method for estimating the water thermohaline structure from satellite data, using a three-dimensional hydrodynamic model and atmospheric reanalysis data. For the Lake Teletskoye, the spectral light attenuation coefficient and underwater irradiance depending on the depth are presented. Inter-annual changes in the bio-optical characteristics of the surface waters of the Barents, Kara, White, Baltic, Black, and Caspian Seas were studied using satellite data. For inland basins (the Gorky Reservoir as an example), a method for estimating the concentrations of chlorophyll and suspension is proposed; the method combines satellite observations and simultaneous registration of the water radiance and a concentration of the optically active components with a portable spectrometer and a fluorescent lidar from a high-speed vessel. An algorithm is developed for restoring the original image of an underwater object distorted by waving; the method is based on approximating the instantaneous shape of the rough surface as a superposition of harmonic waves, which parameters are determined by the sun glint characteristics. The results of the development of several new devices are presented: a sounding spectral meter of fluorescence and scattering; a remote sensing meter of the sea surface characteristics, based on a laser with a beam pattern in the form of a “fan”, and a CCD arrays; a portable hyperspectral complex on a gyrostabilized platform. Various aspects of the influence of the radiation factor on the Earth’s climate system are considered.
The section “Hydrophysics and Saint Petersburg” offers a specific project of a historically reliable memorial dedicated to the Neva floods, with its implementation on the territory of the planned art Park “Tuchkov Buyan”.
The issue presents a research synthesis of one of the essential features of the global climate system — Arctic amplification. The lenses of the Mediterranean water (Meddies) temporal variability analysis is carried out using the theoretical approach of intrusive lens in stratified fluid extended taking into account the Coriolis force. The comparison of volumetric flow rate, heat and salt fluxes on the lateral boundaries of the Lofoten Basin area in the Norwegian Sea is presented as well as estimation of their balances based on ECMWF ORAS4, ORAS5 and CMEMS GLORYS12V1 reanalysis data for the period 1993—2018. An isopycnal advection in the Lofoten Basin is studied based on GLORYS12V1 oceanic reanalysis data. Algorithm of assessment of photosynthetically available radiation near the bottom of the Black Sea shelf is developed and validated based on regional satellite ocean color products and regional spectral bio-optical properties of optically active substances, which profiles are obtained with statistical analysis of long-term measurements from profiling Bio-Argo floats. The results of hydrological, hydrooptical and hydrobiological studies performed in the photic zone of the northern part of the Black Sea in October 2016 are presented. An experimental study of the distribution paths in the Neva River aquatic area one of the most polluted tributaries the Izhora River is carried out based on mathematical modeling and field measurements of total dissolved solids values, as well as additional integral characteristic of water quality — redox potential. A methodology for determining the speed and direction of the sea surface current from measurements of Doppler radar panoramas with an X-band Doppler radar is proposed.