Accuracy Estimation of the Black Sea Circulation Modeling Results Obtained at Different Bottom Topography

Abstract

Purpose. Accuracy of the reconstructed hydrophysical fields calculated using different data on bottom topography is estimated in order to determine the depth array corresponding to the modern tasks of the Black Sea circulation modeling with high spatial resolution. Methods and Results. Two numerical experiments on modeling the circulation were carried out based on the Marine Hydrophysical Institute, Russian Academy of Sciences (MHI RAS) ocean model. Horizontal resolution was 1.6 km, 27 irregular z -horizons were preset vertically and the SKIRON/Eta data (2011) were used as the atmospheric forcing for both cases. Difference between the experiments consisted in application of different bathymetry. In the first experiment, the bottom topography was preset in accordance with the Black Sea depths from the MHI Ocean Data Bank with the 5-minute resolution; in the second one – based on the European Marine Observation and Data Network (EMODnet) depth array with the 1/8ꞌ resolution. The calculated hydrophysical fields were compared with the temperature and salinity measurements, and satellite images of the sea surface temperature. The analysis showed that application of the depths data of higher resolution permitted to improve accuracy of thermohydrodynamic characteristics of the Black Sea circulation in the 30–300 m layer. The integral values of the eddy kinetic energy and the mean current kinetic energy for two experiments were also considered for both of the experiments. The results of the comparative analysis demonstrate the fact that, at the bottom topography with higher resolution taken into account, in the simulated system the mechanisms of energy redistribution between currents and eddies changed during intensive storm impacts. Conclusions. The results of the present research permit to conclude that in the experiment with a smoother bottom relief, increase of kinetic energy both of the eddies and currents was due to barotropic instability. In case of more complex bathymetry, the eddy kinetic energy increased mainly owing to the processes associated with baroclinic instability. eddy, kinetic energy. Acknowledgements: t he authors are grateful to the reviewers for their helpful comments. Experi ment 1 and comparative analyses were performed in the framework of the state task № 0827-2019-0003 “Fundamental study of oceanological processes conditioning state and evolution of marine environment under effect of anthropogenic factors based on observational and modeling methods”. The EMODnet data adaptation for the MHI-model and experiment 2 were carried out under support of the Russian Foundation for Basic Research (project No. 18-05-00353 A).