Physical Oceanography (Aug 2023)
Features of Parameterizing Turbulent Interaction with Underlying Surface in the Regional Thermodynamic Model of Sea Ice
Abstract
Purpose. The study is aimed at assessing the impact of choice of parameterizing the turbulent heat transfer at the ocean – atmosphere boundary upon the basic characteristics of ice regime in the Taganrog Bay apex. Methods and Results. Thermal seasonal dynamics of the snow-ice cover thickness was studied using the non-stationary thermodynamic model of sea ice. The algorithm for defining the turbulent fluxes of momentum, sensible and latent heat in the sea ice regional model is based on the Monin – Obukhov similarity theory. The numerical experiments were performed for the winter seasons of 2007–2008 and 2017–2018, the meteorological conditions of which differed significantly. The transfer coefficients were determined both as the constant values, and as those depending on the atmosphere stratification and the aerodynamic roughness of underlying surface. Implementing stable stratification implied application of three different expressions for determining the stability functions. To avoid the iteration process required for numerical solving of the equations of the Monin – Obukhov similarity theory, the transfer coefficient parameterizations based on the approach relating these coefficients to the bulk Richardson number, were used in the model. Having been analyzed, the results of simulating the evolution of seasonal snow-ice thickness permitted to reveal the features in applying the parameterization of turbulent fluxes. Conclusions. It is shown that the type of parameterizing the turbulent fluxes for the winters characterized by stable frosty weather and ice cover, does not impact significantly the basic elements of ice regime in the Taganrog Bay apex. However, in case the snow-ice cover is highly unstable during a season, the simulation results significantly depend on the method of determining the turbulent transfer coefficients. The best results in reconstructing the seasonal changes in ice cover thickness were obtained when using both the constant coefficients of turbulent transfer CH = CE equal to ≈ 1.7·10-3 and those depending on the atmosphere stratification at the ice geometric roughness equal to 8–10 cm.
