Determination of amplitudes and phases for the annual and semi-annual cycle of the temperature in the Indian Ocean north of 20S from Levitus temperature climatology (1982) gives maximum amplitudes of the seasonal cycle at 100 m with the dominance of semi-annual cycle in the equatorial region and annual cycle elsewhere in the domain. The Bay of Bengal shows characteristics of the westward-propagating Rossby waves of annual period, while the Arabian Sea shows the dominance of Ekman pumping in the central region and westward-propagating features in the eastern region. Qualitative evidences obtained from the distribution of depth of 20°C isotherm and computed Ekman pumping velocities are consistent with the above inferences. From the time-longitude plot of the depth of the 20°C isotherm, the phase speed of westward propagating features from the west coast of India along 10.5N and 15.5N are found to be 7.8 cm s−1 and 5.2 cm s−1 respectively. This is consistent with the corresponding values computed and verified with theory for the Bay of Bengal (Prasanna Kumar and Unnikrishnan, 1995).
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