Abstract. The paper presents the development of the Black Sea community nowcasting and forecasting system under the Black Sea GOOS initiative and the EU framework projects ARENA, ASCABOS and ECOOP. One of the objectives of the Black Sea Global Ocean Observing System project is a promotion of the nowcasting and forecasting system of the Black Sea, in order to implement the operational oceanography in the Black Sea region. The first phase in the realization of this goal was the development of the pilot nowcasting and forecasting system of the Black Sea circulation in the framework of project ARENA funded by the EU. The ARENA project included the implementation of advanced modeling and data assimilation tools for near real time prediction. Further progress in development of the Black Sea nowcasting and forecasting system was made in the frame of ASCABOS project, which was targeted at strengthening the communication system, ensuring flexible and operative infrastructure for data and information exchange between the Black Sea partners and end-users. The improvement of the system was made in the framework of the ECOOP project. As a result it was transformed into a real-time mode operational nowcasting and forecasting system. The paper provides the general description of the main parts of the system: circulation and ecosystem models, data assimilation approaches, the system architecture as well as their qualitative and quantitative calibrations.

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We propose an algorithm of adaptive statistics of prognostic errors aimed at the assimilation of the climatic temperature and salinity fields in a model of dynamics of the sea. The algorithm is used for the numerical solution of the proposed differential equations for the dispersions of prognostic errors of temperature and salinity. The sources in the equations of advective diffusion of heat and salt depend on the four-dimensional dispersions of prognostic errors and one-dimensional (along the vertical coordinate) dispersions of measurement errors. The dispersions of prognostic errors are corrected at the times of assimilation of the data. We perform the reconstruction and analysis of the climatic fields of currents in the Black Sea. It is shown that the structure of the fields of dispersions in the upper mixed layer is determined by the vertical diffusion. Below this layer, the distribution of dispersions depends on the vertical advection. The algorithm of adaptive statistics of prognostic errors allows us to reconstruct the improved mutually adapted hydrophysical parameters with regard for the dynamics of the dispersions of errors.

We compare the thermohaline and dynamic characteristics of the Black Sea reconstructed by using two versions of climatic temperature and salinity fields: old and new . The fields are reconstructed with the help of continuous assimilation of the climatic temperature and salinity in the model. It is shown that the climatic thermohaline fields constructed with regard for the data of observations for the last 20 yr are characterized by an insignificant elevation of the halocline (pycnocline) in the winter-spring period and the elevation of the upper boundary of the cold intermediate layer in the spring-summer period. The intensity of surface geostrophic currents is greater than the same quantity computed on the basis of the old climatic data for the whole year. The horizontal currents in the sea computed according to the new climatic data are more intense.

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