Variations in the Thermal Structure and Wind Field Occurring in the Western Indian Ocean during the Monsoons

摘要

The changes occurring in the temperature field in the Somali Basin and off the Arabian coast have been monitored from October 1975 through December 1979 by a time series of temperature sections obtained along the tanker sea lane offshore between 2 S and 22 N. The development and decay of the large eddy (up to roughly 600 km in diameter) in the northern Somali Basin and its smaller associated eddies were observed each southwest monsoon. Strong horizontal thermal gradients particularly in the upper 200 m occur at the eddy boundaries, and currents in this region can attain velocities of up to 7 knots. Monthly wind stress contoured for the western Indian Ocean clearly shows the southwest monsoon from May through September (with values over 4 dynes/sq. cm during July) to be considerably stronger than the northeast monsoon with a maximum in January. Maps of wind stress curl during the southwest monsoon show a large region of negative curl (over -4 x 10 to the-8th dynes/cc) to the northeast off the somali coast, whereas a region of a high positive curl occurs off the Arabian peninsula and in a small band off the Somali east coast north of 5 N. Sverdrup mass transports of up to 40 x 10 to the -12th g/sec to the north off the Somali coast are in rough agreement with observed values. (Author)