The thermohaline regime trends of the Black Sea basin in the period 2000–2021 were studied based on the data from three retrospective analyses (reanalyses) of the hydrophysical fields of the Black Sea. It is shown that the cumulative effect of an increase in the average sea surface temperature (SST) and increasingly milder winter conditions in the Black Sea over the last seven to eight years led to a record-breaking warming and then to the disappearance of the ventilated cold intermediate layer (CIL) of the Black Sea in its traditional meaning by 2020. In addition, in the past seven to eight years, accelerated warming of seawaters has been observed within the permanent (main) pycnocline. Changes in the thermal regime of the upper layer of the sea are accompanied by a continuing increase in salinity in the main pycnocline.

Purpose. The work is aimed at updating the sea wave forecasting system developed in the Black Sea Marine Forecasting Center by including the block of wind wave forecast in the Sevastopol region and by improving the wave forecast accuracy using the proposed procedure for the SWAN model tuning. Methods and Results. In the updated forecasting system, the possibility of performing the joint operational sea wave forecasts for the Black Sea and the Sevastopol region (with the 5 and 1 km spatial resolutions, respectively) became possible due to the nested grid method applied. To improve accuracy of the wave forecasts, the procedure for the SWAN model tuning was proposed. It is based on changing the parameterization of the surface friction coefficient C-d(V), where V is the surface wind speed. This permits to reduce the deviations of the forecasted wave heights from those obtained from the satellite altimetry measurements. Efficiency of the proposed procedure was assessed through comparison of the forecasting results with the remote sensing data. It is shown that in the forecasts supplied with an optimal choice of functional dependence C-d(V), the scattering index between the forecasted and measured values can be reduced by 20 %. Conclusions. Represented is the updated system of the Black Sea Marine Forecasting Center intended for the joint operational sea wave forecasts in the Black Sea and in the Sevastopol region. The results of model validation have shown that the procedure proposed for tuning the SWAN model makes it possible to reduce the deviations of the forecasted wave heights from those measured by the sensors installed at the altimetry satellites.

Информация о полях скорости поверхностных морских течений является востребованной при решении широкого круга океанологических задач.На сегодняшний день основными источниками этих данных являются спутниковые альтиметрические измерения и результаты расчётов с использованием морских гидродинамических моделей.Кроме этого, в последние годы всё чаще используются методы восстановления полей скорости при помощи анализа последовательностей спутниковых изображений в оптическом и инфракрасном (ИК) диапазонах.В силу отсутствия эталонных данных о поверхностном потоке актуальной задачей является анализ точности расчётов на основе сопоставления имеющихся результатов, полученных из разных источников.В статье представлены результаты синхронизированных расчётов полей скорости поверхностных течений в акватории Чёрного моря с использованием трёх источников данных.Расчёты проводились для двух ситуаций с минимальным присутствием облачности.Для каждой из них были получены: 1) поле скорости, рассчитанное по сериям снимков NOAA AVHRR в ИК-диапазоне с использованием методики четырёхмерной вариационной ассимиляции; 2) модельное поле, соответствующее глубине 2,5 м; 3) геострофическая компонента скорости поверхностного потока, определённая с использованием спутниковой альтиметрии.Продемонстрированы сходства и различия мезомасштабных структур в полученных полях.Статья может быть интересна специалистам в области морской гидродинамики, а так

The results of the Black Sea uniform mixed layer (UML) thickness determination were used for investigation of its spatio-temporal variability based on numerical calculations of the monitoring and forecasting center of the Black Sea (BS MFC). The spatial distribution of the mean and standard deviations of the UML depths in the Black Sea has been studied over the seven-year period. The time series analysis of UML thickness was performed by their spatial averaging over the Black Sea area for each day of the seven-year period. The principal components of the variability of the spatio-temporal UML depths field have been studied. The areas of high and low UML depths variability and the frequency-time characteristics of their variations have been determined.

The paper considers the matters of numerical modelling and forecast estimation accu-racy of sea surface temperature in the two monitoring and forecasting centers of the Black Sea - in Federal State Budget Scientific Institution "Marine Hydrophysical Institute of RAS" (FSBSI MHI) and Copernicus marine environment monitoring service. The CTD (Conductivity Temper-ature Depth) profiling data of in situ measurements from research vessel "Professor Vod-yanitskiy" were used to solve the problem. Spatial and temporal mismatch between the model data and in situ measurements was eliminated to form a joint sample of these two data sources. Comparison was performed for the time period from October 2017 to September 2018 and showed that the forecasting results of sea water temperature in FSBSI MHI are more reliable than in Copernicus marine service for all forecast terms.

The intense storm passed over the Black Sea during about half a day in November 2007. The operational hydrodynamic model which was used at the Marine Hydrophysical Institute at that time, simulated the variability of sea basin fields in a wide range of spatial and temporal scales. One of the interesting aspects of marine dynamics is the excitation of highly intense inertial oscillations across the basin. Inertial oscillations are originally developed in the surface sea layer and have high spatial coherence. Their intensity decreases with time. The damping of inertial oscillations in the upper sea layer is caused by their propagation deep into the sea. The main characteristics of oscillations are presented, and the requirements to the circulation model for their more accurate quantitative description are discussed.

The results of the Black Sea uniform mixed layer (UML) thickness determination are presented in the article and based on using the vertical profiles of seawater temperature obtained by three-dimensional numerical model over a five-year period. The method of adjusting the parameters of automated algorithms to determine the UML depth is proposed with the help of which three known methods of determining this parameter were implemented. The obtained results were used to study the relationship between the UML depth and the changes in the parameters of the atmospheric boundary layer at night time. It is shown that the data of heat fluxes, short-wave solar radiation, wind stress and bulk Brunt-Vaisala frequency can explain of up to 65% UML depth dispersion on the basis of regression analysis by using factor models.

The paper considers the matters of numerical modeling estimation accuracy of temperature and salinity three-dimensional fields in the monitoring and forecasting center of the Black Sea. Automatic system of analysis and forecast of the Black Sea state is run in the center in an operational mode. The data of in situ measurements from ARGO profiling floats regularly provided by the European Marine Forecasting Service – Copernicus – were used to solve the problem. Spatial and temporal mismatch between the model data and in situ measurements was eliminated to form a joint sample of these two data sources. Comparison is performed for the time period from 2012 to 2015. The results show quite good simulation accuracy of the ther-mohaline fields, however, the problems of modeling the temperature fields in the 5-30 m layer were detected where there is a fairly narrow seasonal thermocline in late spring, summer and early autumn.

The Copernicus Marine Environment Monitoring Service is one of six services (ocean, atmosphere, land, emergency situations, security and climate changes) launched by the European Union within the EU Earth observation program.The data in the monitoring system covers both the entire World Ocean and individual European basins.The paper reviews the products of the Copernicus Marine Service operational system available in the Arctic.At the present time this region is of the increased interest both in Russia and in the world community.The system products include information on the thermodynamic, biogeochemical and bio-optical state of the marine environment.The system products are accessed through the electronic catalog of products.Selection criteria and possibilities for searching interesting information through the interactive web-portal are given in the paper.The system products containing the data of model calculations, satellite and in situ measurement results are considered.Spatial and temporal characteristics of the products are given, information on by whom, how the product was obtained and what is its accuracy is represented.The results of the system products visualization by the integrated tools (they allow one to construct and analyze time series, profiles, horizontal and vertical sections) are shown.All the system data is publicly available to the registered users.Regular changes and updates of the system products as well as the mechanisms for accessing them take place.This information is sent to users by e-mail and is available on the news flash of the web-portal.

The automatic system of operational forecasting of the Black Sea state which functions at the Marine Hydrophysical Institute is presented. Principles of the system construction are considered; the marine environment models used for forecasting, the data streams required for the system functioning, and tools for validating and visualizing the results of sea-state calculations are described. Some examples of investigating a number of processes and phenomena in the Black Sea are given.

Problems of reliability control of the atmospheric forcing data used for setting boundary conditions in the model simulations performed in the Black Sea marine forecasting center (BS MFC) of MHI (RAS) are considered. To set the boundary conditions on the sea surface it is necessary to have information about the heat, momentum, evaporation and precipitation total fluxes and short-wave radiation penetrating in the upper sea layer with a thickness of about fifty meters. To check the reliability of the data obtained the information not only about these fluxes, but also about their components appears to be of high value. The first section describes the weather forecasts applied in BS MFC for the atmospheric boundary layer. The methods for controlling the weather forecast reliability of the atmosphere boundary layer are considered. The software developed to solve this task is briefly described in the second section. The first group of control methods is based on the calculation according to the approximate formulas short-wave and long-wave radiation fluxes. For other components of total fluxes their comparison according to the forecast data of two atmospheric models used in BSMFC to set the boundary conditions on the sea surface is used. The third section contains the examples of the errors occurring in preparing the weather forecast data. Errors in the data on the magnitude of the albedo and upward short-wave radiation fluxes were discovered on the basis of the application of the developed methods. The conclusions drawn from the results obtained testify to effectiveness of the system developed to control data reliability. Further investigations are planned. It is noted that the results represented in the paper constitutes a basis for development of the software intended to correct the revealed errors.

Operational monitoring system is developed to automatize the process of diagnosis and forecast of hydrological fields of marine environment in the Sevastopol Black Sea region based on the local hydrodynamical model POM. The initial and boundary conditions for the local model are set from the basin model of the Black Sea dynamics. The data obtained by SKIRON Regional Forecast Center of Athens University is applied as the atmospheric effect. For the parameterization of vertical mixing in local circulation model Pall turbulence model based on turbulence hypotheses of Rott - Kolmogorov and generalized by Mellor and Yamada in the case of a stratified flow is included. The model takes into consideration the penetration of the short-wave solar radiation into the water column. System automation is implemented using the CalcMan software package which is an own development of Marine Hydrophysical Institute. The output fields are accessible in the NetCDF format with horizontal spatial resolution constituting 1 km, vertical resolution - 18 irregular levels from 2.5 to 1000 m and time resolution - 3 hr. The system provides a possibility of daily updating the forecast data. Based on the THREDDS server, the specialized visualization subsystem is installed and configured to visualize and disseminate simulations results. Its user-friendly interface allows a server-side analysis of all the forecasted fields, permits to construct horizontal and vertical sections, vertical profiles and time series, to create animated pictures without downloading the data to a client's side. OPENDAP and NetcdfSubset interfaces are used for disseminating data in a digital form.

We consider some specific features of creation of the database according to the results of drifter experiments carried out in the Black Sea in 2001–2006. The general statistical information on all buoy studies in the sea is presented. The criteria used to filter the primary data are suggested. The principles of formation and structuring of the drifter database are presented. As an example, we describe the procedure and the results of comparison of model estimates with the data of contact measurements of the sea-surface temperature by drifting buoys.

Multicomponent system for Black Sea dynamical processes diagnoses and prognoses, developed in MHI UNAS, is presented. The temperature, salinity, sea level, currents velocities and sea wave's fields can be monitored and predicted by means of this system. The monitoring and prediction results are transmitted via Internet.