Diagnostic circulation model for the sensitivity of eddy viscosity coefficients in the western tropical Indian Ocean

Abstract

The sensitivity of a 18-level diagnostic model of circulation to two different values of horizontal eddy viscosity coefficients has been investigated. Vertical eddy viscosity coefficient has been kept constant in both the experiments. Model driven with January mean wind and thermohaline fields attained steady state within 15 days of model integration. Computed results at 10, 100 and 500 m depth for both the experiments are presented in this paper. Circulation features at 10 m depth in terms of both the magnitude and direction are identical for both the numerical experiments although the horizontal eddy viscosity coefficient was increased two-fold in the second experiment. However, the magnitude of circulation at 100 and 500 m depths was found to decrease marginally in those regions where strong currents were observed. Dynamics of circulation at the above mentioned depths is explained in terms of the forcing parameters and other dynamical. characteristics of the model. It has been found that the surface circulation is mainly controlled by wind field and the subsurface circulation patterns by thermohaline forcing.