Seasonal and interannual variations in the Indian Osean

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A holizontally high resolution Indo-Pacific ocean general circulation model, which can resolve the detailed geometry and bottom topography in the Indonesian archipelago as well as the whole Indo-Pacific region, is developed and used to investigate seasonal and interannual variations in the upper layr thermal structure and the circulation in the Indian Ocean and the Indonesian Throughflow. The outcomes of this study are as follows :(1) Simulated seasonal variability of the Indonesian Throughflow, seasonal and interannual variations of the upper layr thermal structure in the Indian Ocean are both consistent with the observed data such as the XBT and CTD data, the sea surface height variations derived from satellites, the surface drifting buoys, and the tide gauge dada. This indicates that the numerical model is an efficient tool to investigate the seasonal and the interannual variability in the Indian Ocean.(2) The seasonal variability of the Lombok throughflow consists of the annual and … More the semiannual harmonics. While the annual siganl is forced by the local monsoonal winds over the Indonesian archipelago, the semiannual signal is associated remotely with the Kelvin waves generated twice a year during the monsoon transition time in the central equatorial Indian Ocean. On the other hand, the coastally trapped waves around Australasia, which are forced by the winds along the southwestern coast of Australia associated with the meridional movement of the southern hemisphere westerlies, play an important role in the seasonal transport variation through the Timor Sea. Furthermore, the simulated annual-mean Throughflow does not show the simple Sverdrup dynamical balance. It turns out that considerable concellation of terms in the momentum equation is involved in producing a near-Sverdrup balance in the model.(3) The seasonal and the interannual variations of the simulated and the observed depth of the 20ﾟC isotherm show a band of large amplitude between 8ﾟS and 20ﾟS across the Indian Ocean, and the signals propagate to the west. The generation of those signals is well explained by a simple model which consists of the local Ekman pumping velocity and the nondispersive, long Rossby waves. The signal radiating from the eastern boundary of the Indian Ocean contributes only about 10% of the annual signal ; however, it affects the interannual variations in the eastern part of the southern tropical Indian Ocean. Less