Biological wastewater treatment plants (the BTPs) of city of Odesa (Northern and Southern Plants) are the most powerful permanent sources of nutrient pollution of coastal waters of Odesa Region of the north-western part of the Black Sea (the NWPBS) and the Khadzhybei Liman. The article includes a comparative analysis of changes, taking place since the beginning of the 21st century, related to the qualitative composition of return water of the Northern and Southern BTPs and the amount of nutrients reaching the marine environment together with such water, as well as the analysis of possible influence of such changes on eutrophication of coastal waters of Odesa Region of the NWPBS and the Khadzhybei Liman. It was established that despite significant decrease (by 1.7 - 2 times) of return water discharged from the BTPs the amount of nitrates and nitrites reaching the marine environment together with such water increased by 4-6 times. At the same time the reduced inflow of organic matter, ammonium nitrogen and phosphates can be observed. Treatment facilities of Odesa were put into operation back in the 1970s. They use a then typical technology of biological cleaning of wastewater from nutrient compounds in aeration tanks providing aerobic conditions. The technology is considered as incomplete in terms of nitrogen compounds treatment since its final product includes nitrate nitrogen in large quantities. When reaching the marine environment it is absorbed by algae at the stage of primary production of organic matter and thus is transformed in organic nitrogen again. It was noted that since the coastal waters of Odesa Region of the NWPBS and the Khadzhybei Lyman have a high level of trophicity and currently there is a disbalance between mineral nitrogen and phosphorus concentrations in the water towards insufficiency of mineral nitrogen reserves (as compared with the standard Redfield stoichiometric ratio), additional inflow of nitrates and nitrites in the marine environment together with return water from the BTPs would, in certain circumstances, lead to algal bloom and aggravation of negative eutrophication-related consequences. The research allowed making a conclusion that a modern flow sheet of advanced biological cleaning (treatment) of wastewater from nitrogen compounds should be implemented at the Northern and Southern BTPs in order to reduce the inflow of nitrates in the marine environment. Such flow sheet should ensure both nitrification and denitrification processes.

The convection-permitting Harmonie model is considered as a modeling component of the atmosphere-sea system. The role of the atmospheric model in the system is to create upper boundary conditions for marine environment model with high spatial (1-2.5 km) and temporal (from one minute to one hour) separating capacity. The research offers description of major modules which govern the configuration, spatial-temporal parameters of the atmospheric model and the way they are implemented in the High Performance Computing Facilities System (the HPCFS) of the European Center for Medium-Range Forecasting (the ECMWF). The use of the HPCFS and direct connection to global output data of the Integrate Forecasting System (the IFS) allows online performance of numerous calculations. The research shows the results of a numerical experiment for the north-western part of the Black Sea and neighbouring continental regions during severe weather conditions with strong wind speeds in January 2018. The high resolution modeling demonstrated high performance parameters of the model when reproducing mesoscale features of the atmospheric circulation. They are as follows: division of two lower-level jets in the north-western atmospheric flow along the coast line; mesoscale offshore patterns associated with thermal contrast and wind shear over different surface types along the coastal area; weaker circulations over regional bays on lee sides. The advantages of the Harmonie model comparing other modeling systems when determining the upper boundary conditions for modeling of the marine environment over offshore regions are listed. In particular, the model has direct access to the ECMWF archive and IFS operational global model output data; assimilation methods use all data available for observation; numerous parameterization schemes can be tuned for different climate zones and specific areas; post-processing provides more than two hundreds of physical, dynamical and chemical output variables at different types of levels, such as isobaric surfaces, model levels, geometric altitudes; output format list includes grib, netcdf and simple text which allows use of results both for their further direct introduction into the marine model and plotting fields, cross-sections and profiles in the metview visualization package.

In order to solve the problems of diagnosis and forecast of spatial-temporal variability of hydrological characteristics of the Kuyalnik Liman (water level, salinity and temperature) which cause chemical and biological processes occurring therein, and, therefore, affect the properties of brine and therapeutic mud, a non-stationary 3D numerical hydrothermodynamic model Delft3D-FLOW was applied. The model can be applied for research of the features and forecasting of spatial-temporal variability of hydrological characteristics of the Kuyalnik Liman under the influence of natural and anthropogenic factors forming its hydrological regime. Such opportunity is also indicated by the results of adaptation of the model to the Kuyalnik Liman conditions and its validation that are specified in this work. The important role of accounting of small streams flowing into the liman and accurate setting of intensity of storm rainfall during modelling is also shown. It is found that at the time of storm winds with longitudinal directions in relation to the liman’s water surface, the difference of watermarks in its northern and southern parts may reach 0.35-0.4 m.

The paper is devoted to discussion of the prospects of simplified 2D hydrodynamic model use aimed at forecasting the wind-induced sea level fluctuations within the area of sea ports (Chornomorsk, Odesa and Yuzhnyi) of the Odesa Region in the North-Western part of the Black Sea. Spatio-temporal variability of wind conditions at the sea-atmosphere division is specified based on the data of the global numerical weather prediction model of the Global Forecast System (GFS). The research includes the description of the mathematical structure of the hydrodynamic model and the results of its adaptation to the conditions of the simulated sea area. It presents the results of model verification in the version which implies adoption of wind data from the archives of GFS-analysis and GFS-forecasts for 2010, 2016 and 2017. The verification was performed by comparing wind-induced denivellations of the sea level at the ports of Chornomorsk, Odesa and Yuzhnyi calculated over the course of modelling and those established on the basis of observational data (with the discreteness of 6 hours). A quantitative assessment of the calculation accuracy was performed for the cases where, according to the observational data, level denivellations exceeded the value of the standard deviation for the entire series. New series of the observed and calculated model-based significant wind-induced denivellations of sea level were formed for each of the ports from the sets of samples that met this condition. Using  these series estimates of the mean square error of the calculations, allowable error of calculations, correlation coefficient between the actual and calculated values of the level denivellations, the probability of the calculation method under the allowable error were obtained. It was established that in the case of use of the data from wind GFS-analysis (with spatial resolution of 0.5° both latitudinally and longitudinally) over the course of modelling the probability of calculation of significant sea level denivellation constitutes 84-85%, and in case of using the data from the GFS-archive of wind forecasts (with spatial resolution of 0.25°) – 88-91%. This allowed making a conclusion that the model has good prospects of use for operational forecast of the sea level fluctuations caused by storm wind in the version implying assimilation of the predicted information on the spatio-temporal variability of wind conditions obtained by means of the GFS global weather forecast model.

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