Influence of the Vertical Turbulent Exchange Parameterization on the Results of Reanalysis of the Black Sea Hydrophysical Fields

• Main Authors: L.I. Sukhikh, V.L. Dorofeyev
• Format: Article
• Language: English
• Published: Federal State Budget Scientific Institution «Marine Hydrophysical Institute of RAS» 2018-08-01
• Series: Physical Oceanography
• Subjects: reanalysis; black sea dynamics; numerical modeling; data assimilation
• Online Access: http://physical-oceanography.ru/repository/2018/4/en_201804_02.pdf

Comparative analysis of two simulations of the Black Sea hydrophysical fields’ long-term variability in 1993–2012 is performed. Two reanalyses are done using various methods of parametrizing the vertical turbulent exchange in the circulation model. The first variant implies a simple parameterization including the constant coefficient of vertical turbulent viscosity and the coefficient of vertical turbulent diffusion in a form of climatic profiles. The second simulation includes the turbulence model of the Mellor-Yamada type to parametrize the vertical exchange processes. Having been compared, the reanalysis results and the measurement data show that application of the turbulent model for parametrizing the vertical exchange yields a better description of the Black Sea water thermohaline structure. In particular, structure of the summer seasonal thermocline and location of the main halocline (in both of them maximum deviations of the model temperature and salinity from the in-situ measurement data are observed) are reproduced more accurately. Different methods of parametrizing the momentum vertical exchange influence the horizontal circulation vertical structure. The first variant of simulation shows that a significant part of the currents’ kinetic energy is concentrated in the thin 10-m layer, and this fact affects the circulation features of shallow water on the northwestern shelf; whereas the simulation based on the turbulent model implies more intensive transfer of the kinetic energy to the lower layers. The carried out investigation shows that the results of the hydrophysical fields’ reanalysis depend on accurate description of the thermodynamic processes in the sea upper layer and the vertical turbulent exchange ones, in particular.