Results from a numerical model of the northern Indian Ocean: circulation in the south Arabian Sea

A three-dimensional primitive equation numerical circulation model has been applied to the northern Indian Ocean. The model domain extends from 20 deg rees S to the Asian continent in the north and from Africa in the west to 1 20 degrees E. The high vertical resolution of the model enables a better de piction of the vertical structure and processes in the upper layers than ha s been hitherto possible, The model also accounts for the large fresh water inputs from rivers on the Indian subcontinent. We describe here the result s from a climatological simulation forced by monthly climatological winds, focusing principally on the southern Arabian Sea. The model results are sup plemented with observational data from the NASA TOPEX altimeter to study th e circulation in the northern Indian Ocean. Overall, the model successfully captures many of the important circulation features observed. This include s the reversing Somali Current in the Arabian Sea and the equatorial curren t system. Along the southwest coast of India, an anticyclonic feature known as the c has been observed to form during northeast monsoon and propagate to the west. A cyclonic feature also forms in the same location during the southwest monsoon. The formation and propagation of these features are cent ral to the circulation and variability of the southern Arabian Sea and are clearly seen in TOPEX altimetric records for 1993 and 1994. They are also r easonably well depicted in the climatological simulations presented here. ( C) 2000 Elsevier Science B.V. All rights reserved.