Seasonal and Interannual Changes in the Structure of Currents, Obtained on the Basis of the Improved Version of the MHI Model and Data Assimilation in the Summer and Autumn-Winter Seasons of 2016 and 2017

Based on four numerical experiments with assimilation of CTD sounding data (28.06–18.07.2016, 15.11–05.12.2016, 13.06–03.07.2017, 14.11–05.12.2017), the analysis of the features in the field of the Black Sea currents was carried out depending on the season and year. To implement calculations, we used a numerical model developed at the Marine Hydrophysical Institute, taking into account new approximation schemes for advective terms in the heat and salt transfer equations that ensured simultaneous conservation of temperature to the first and n-th (n > 1) powers and salinity to the first and m-th (m > 1) powers. The calculations were made using high spatial resolution (horizontal grid ~1.6 × 1.6 km and 27 vertical layers) and ERA5 atmospheric forcing. Based on the analysis of energy characteristics and vertical sections in the density field, possible physical mechanisms for the formation of eddies were considered.