Upwelling off the Southwest Coast of India

Abstract

Various factors responsible in inducing upwelling are discussed. A distinction is made between the process of upwelling: and its etlects on the environmental conditions. Upwelling off the southwest coast of India is discussed in relation °to the time variation of density structure , horizontal divergence of surface Current vectors, wind stress components - parallel and perpendicular to the Coast, thermal structure and sea level. Upwelling in this region commences in the deeper layers of about 90 m in March a nd the upwelled water reaches the surface by May. The process continues to occur vigorously till June. From then, with the increase in strength of southwest winds, intensity of upwelling reduces and finally ceases to be present by July/August when the onshore winds of the southwest monsoon have maximum strength. The reverse process, sinking, sets in by September. Ve rtical velocity, i.e. upwelling, calculated (1) from the vertical shift of the isopycnal with time and (ii) from the average horizontal divergence, is 1•5 X 10-s and 1•8 x 10-s em sec-1 respectively.