Modelling the spring-summer evolution of the thermohaline structure in the Gulf of Finland on the basis of a three-dimensional hydrodynamic model of high resolution

To improve the quality of simulation of thermohaline structure in the Gulf of Finland a three-dimensional hydrodynamic model is proposed. It is based on the model complex NEMO (Nucleus for European Modelling of the Ocean). Angular steps of the model grid on latitude and longitude are, respectively 0.25 and 0.5' (≈ 0.5 km), that is 4–8 times less than the value of the baroclinic Rossby deformation radius in the Gulf of Finland. Vertical turbulent exchange is described using a turbulent closure scheme of k-ε type. The calculation results are compared with contact measurements of temperature and salinity obtained using CTD probe at 38 stations in the expedition of the Russian State Hydrometeorological University in the eastern Gulf of Finland in the period from 25 to 28 July, 2011 and data CTD probe (15 stations) for the summer period, 2011 from the BED (Baltic Environment Database). Calculated sea surface temperature is also compared with its satellite estimates, having a resolution of 1×1 km and obtained by the Moderate-resolution Imaging Spectroradiometer (MODIS). It is shown that the choice of the appropriate scheme of turbulent closure and implementation of the model on the grid of high-resolution (≈ 0.5 km) led to significant improvement (compared with the calculations on a coarse grid) of the quality of simulation of temperature in the spring-summer period.

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