Introduction

The Somali Current is the most dramatic feature of the seasonally reversing circulation in the northern part of the western Indian Ocean. At its peak, at the height of the southwest monsoon, surface currents of 3 to 4 ms-1 have been reported, and its total transport has been estimated at 70 million tonnes per second. The present state of knowledge of this current has been thoroughly reviewed in two recent papers, by Düing (1978) on observations and by Anderson (1978) on theoretical studies. From the point of view of monsoon dynamics, there are two particularly significant aspects. For monsoon meteorologists, the upwelling related to the Somali Current and its effect on sea-surface temperatures in the western Indian Ocean may be most important. For dynamical oceanographers, the onset of the Somali Current has been a particular concern: how do the monsoon winds generate such a strong current so quickly? The purpose of this chapter is to briefly review observations that bear on these two aspects of the Somali Current. First, though, for the benefit of those to whom it may be unfamiliar, a short description of the fullydeveloped current will be given.

The fully-developed Somali Current

It is convenient to think of the Somali Current as the seasonally reversing part of the boundary current along the east coast of Africa; that is, the part extending northwards from approximately 3° S latitude.