Semidiurnal and diurnal barotropic currents in the inner shelf and surf zone of the west coast of India: Measurements and modeling

We study the dynamics of barotropic currents at semidiurnal and diurnal frequency bands in the inner shelf and surf zone off the west coast of India using moored velocity observations. In both the Inner shelf and the Surf zone, the observed current exhibits significant semidiurnal and diurnal energy. The hourly climatology of residual currents exhibits a strong diurnal variability in the barotropic currents in the both regions. A 2D hydrodynamic model, Delft3d, was implemented, and sensitivity experiments were performed to understand the role of wind and wave in the tidal and diurnal variability of barotropic currents in the region. Surf zone barotropic currents in diurnal band are strongly modulated by the winds. However, wind has minimal influence on the barotropic current in the inner shelf. Sensitivity experiments with and without waves show that, apart from wind, wave parameters have significant influence on the diurnal variability of surf zone currents. Analysis further confirms that diurnal currents in the surf zone are primarily wind-driven, while inner shelf currents are mostly tide-dominated. Overall, this study underscores the necessity of incorporating wind, wave, and tidal forcing to realistically simulate nearshore currents in the inner shelf and surf zone along the west coast of India.