Analysis of the Dynamic and Energy Characteristics of Water Circulation near the Western Crimea Coast and in the Sevastopol Region Based on the Observational Data Assimilation in the Numerical Model of the Black Sea Dynamics

S. G. Demyshev, N. A. Evstigneeva✉, D. V. Alekseev, O. A. Dymova, N. A. Miklashevskaya

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: naevstigneeva@yandex.ru

Abstract

Purpose. The study is aimed at evaluating effectiveness of the procedure of the observational data assimilation using the Kalman filter algorithm as compared to sequential analysis of the hydrophysical fields based on the optimal interpolation method, and at analyzing the mesoscale features of coastal circulation near the western Crimea coast and in the Sevastopol region.

Methods and Results. Based on the hydrodynamic model adapted to the Black Sea coastal zone conditions including the open boundary and on the temperature and salinity data from the hydrological survey in 2007, the dynamic and energy characteristics of the Black Sea coastal circulation were calculated with high spatial resolution (horizontal grid is ~ 1.6 × 1.6 km and 30 vertical horizons). The hydrophysical fields were reconstructed using two algorithms of data assimilation: the sequential optimal interpolation and the modified Kalman filter. The kinetic energy changed mainly due to the wind action, vertical friction and the work of pressure forces; the potential energy – due to the potential energy advection and the horizontal turbulent diffusion. The following circulation features were reconstructed: the anticyclonic eddy with the radius about 15 km in the Kalamita Bay in the water upper layer, the anticyclonic eddy with the radius about 15 km between 32.2 and 32.6° E in the whole water layer, the intense current near Sevastopol and along the Crimea western coast directed to the north and northwest, and the submesoscale eddies of different signs of rotation in the upper layer.

Conclusions. It is shown that having been taken into account, heterogeneity and non-isotropy of the error estimates of the temperature and salinity fields relative to the correlation function lead to qualitative and quantitative differences in the hydrodynamic fields (amplification of currents, change of the currents’ direction and eddy formations were better pronounced). At the same time, the mean square errors of the thermohaline fields’ estimates decreased. Formation of the anticyclonic eddy with the radius about 15 km in the Kalamita Bay could be related to the current shear instability. Submesoscale eddies with the diameters less than 5 km were formed when the current flowed around the coastline and the bottom topography inhomogeneities.

Keywords

Black Sea, numerical simulation, high spatial resolution, assimilation of observational data, mesoscale and submesoscale eddies

Acknowledgements

The authors are grateful to the reviewers for their helpful comments. The circulation mesoscale features reconstructed using the data of the hydrological survey in 2007 was analyzed at the financial support of the Russian Foundation for Basic Research and the city of Sevastopol within the framework of scientific project No. 18-45-920019. The assimilation procedure based on the Kalman filter was continued to be improved within the framework of the state task on theme No. 0827-2019-0002.

Original russian text

Original Russian Text © The Authors, 2021, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 37, Iss. 1, pp. 23-40 (2021)

For citation

Demyshev, S.G., Evstigneeva, N.A., Alekseev, D.V., Dymova, O.A. and Miklashevskaya, N.A, 2021. Analysis of the Dynamic and Energy Characteristics of Water Circulation near the Western Crimea Coast and in the Sevastopol Region Based on the Observational Data Assimilation in the Numerical Model of the Black Sea Dynamics. Physical Oceanography, 28(1), pp. 20-36. doi:10.22449/1573-160X-2021-1-20-36

DOI

10.22449/1573-160X-2021-1-20-36

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