Dynamics of Oceanic Processes Department

⎯The upwelling of deep water associated with the influence of cyclonic wind curl and the difference in the buoyancy of the inflows in the lower and upper water layers is observed in the central part of the Black Sea. The resulting vertical water motions contribute to the transport of ammonium to the upper boundary of the anaerobic zone. In the suboxic zone, ammonium is converted to nitrate via nitrite as a result of the nitri-fication, and thus it can supply the nitrocline in the water basin. Within the framework of this paper we discuss the effectiveness of this mechanism on the basis of the numerical simulation. The calculations were performed using a one-dimensional physical-biogeochemical model for the upper 600-m sea water layer, which takes into account seasonal variations in atmospheric parameters and vertical motions. The model describes the biological and redox processes in the suboxic zone. We have estimated the contribution of different constituents into the balance of nitrogen compounds in the euphotic water layer. It is shown that ammonium nitrogen coming from the deep water due to vertical water motion plays a significant role in maintaining the balance of nitrates in the central part of the Black Sea.

Исследуется влияние сезонной изменчивости вертикальной скорости на формирование поверхностной солености в центральной части Черного моря. Проведены расчеты по одномерной
гидродинамической модели с учетом постоянной и переменной во времени вертикальной скорости. Дана оценка объема воды и соли, который поступает к периферии бассейна из центральной глубоководной части Черного моря.

This paper considers the main steps in improving the methods for calculating the ocean (sea) dynamics on the basis of observational data on sea-water temperature and salinity. The results of diagnostic and adaptation calculations for the near-equatorial area of the West Atlantic in the area of the Lomonosov countercurrent formation are presented. We consider the problem of the complex use of measurements of temperature, salinity, and current velocity in the POLYMODE polygons with their assimilation into the model using a Kalman filter. The results of calculations of the coordinated fields with the mechanism of geostrophic adaptation and using asynchronous measurements obtained by the Razrezy program are given. We discuss further modifications of the assimilation algorithms for hydrological observation data in models of sea dynamics and the principles of adaptation of hydrophysical fields that made it possible to reconstruct the climate fields of the Black Sea and to reproduce the basin dynamics for 23 years.

We realize the algorithm of adaptive statistics of forecasting errors for the assimilation of the climatic fields of temperature and salinity in the σ-coordinate model of the dynamics of the Black Sea. The principal relations of this algorithm and its simplified version based on the Kalman filter are presented. The distinctive features of realization of the algorithm specified by the model are discussed. We also present the results of comparison of the hydrophysical fields of the Black Sea reconstructed according to the algorithm of adaptive statistics and a simplified scheme of assimilation of the climatic data. It is shown that the dependence of sources in the transport equations (heat and salt diffusion) on the four-dimensional variances of forecasting errors and threedimensional measurement errors enables one to reconstruct the mutually adapted climatic parameters of the sea more exactly.

Since 1997 the U.S. satellite sensor SeaWiFS is providing an information, that can be helpful to monitor Black Sea waters in routine operational mode. Due to the errors inherent in atmospheric correction procedures, the possibilities to determine the full spectrum of normalized spectral water-leaving radiance are very limited. At the same time the analysis shows that the use of two SeaWiFS channels at 510 and 555 nm allow us to detect many interesting features of temporal and spatial variability of the effects of absorption and scattering of light in the Black Sea.

Main cold intermediate layer (CIL) parameters are estimated using reanalysis data from Black Sea Marine Forecasting Center (BS MFC) and CMEMS (Copernicus Marine Environment Monitoring Service) for 1993 – 2013. Seasonal and interannual variability of CIL characteristics for both data sets are investigated and intercomapared.