DIAGNOSTIC CIRCULATION MODEL FOR THE SENSITIVITY OF EDDY VISCOSITY COEFFICIENTS IN THE WESTERN TROPICAL INDIAN-OCEAN

The sensitivity of a 18-level diagnostic model of circulation to two d ifferent values of horizontal eddy viscosity coefficients has been inv estigated. Vertical eddy viscosity coefficient has been kept constant in both the experiments. Model driven with January mean wind and therm ohaline fields attained steady state within 15 days of model integrati on. Computed results at 10, 100 and 500 m depth for both the experimen ts are presented in this paper. Circulation features at 10 m depth in terms of both the magnitude and direction are identical for both the n umerical experiments although the horizontal eddy viscosity coefficien t was increased two-fold in the second experiment. However, the magnit ude of circulation at 100 and 500 m depths was found to decrease margi nally in those regions where strong currents were observed. Dynamics o f circulation at the above mentioned depths is explained in terms of t he forcing parameters and other dynamical. characteristics of the mode l. It has been found that the surface circulation is mainly controlled by wind field and the subsurface circulation patterns by thermohaline forcing.