Tropical Oceanography

This chapter describes the different aspects of tropical oceanography. The character of the oceanic variability depends on the time scale of the wind changes and also on time scales intrinsic to the ocean. The eastward winds that prevail over the central Indian Ocean at the time of the equinoxes generate the intense oceanic jet. To explain the behavior of the jet, an appealingly simple model of the tropical ocean will suffice. In the model, the interface between two layers of immiscible fluid, each of constant density, simulates the sharp and shallow tropical thermocline that separates the warm surface waters from the cold waters of the deep ocean. The motion induced by the sudden onset of spatially uniform zonal winds, which then remain steady, is initially independent of longitude provided that attention is confined to regions distant from the coasts. It is found that the Kelvin wave is confined to the narrow equatorial zone such that the oceanic adjustment outside this zone proceeds entirely from the eastern coast and is effected by Rossby waves. It is suggested that the models that take the three-dimensional structure of the tropical oceans into account are necessary to simulate its low-frequency variability.