Large-scale processes in the upper layers of the Indian Ocean inferred from temperature climatology
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).
Unnikrishnan, A. S., S. P. Kumar, and G. S. Navelkar. 1997. "Large-scale processes in the upper layers of the Indian Ocean inferred from temperature climatology." Journal of Marine Research 55, (1). https://elischolar.library.yale.edu/journal_of_marine_research/2219