A Holistic Approach to Upwelling and Downwelling along the South-West Coast of India

An attempt has been made to develop a holistic understanding of upwellingand downwellingalong the south-west coast of India. The main objective was to elucidate the roles of different forcings involved in the vertical motion along this coast. The south-west coast of India was characterized by upwellingduring the south-west monsoon (May to September) and by downwellingduring the north-east monsoon and winter (November to February). The average vertical velocity calculated along the south-west coast from the vertical shift of the 26 �C isotherm is 0.57 m/day during upwellingand 0.698 m/ day during downwelling. It was concluded that upwellingalong the south-west coast of India is driven by offshore Ekman transportdue to the alongshore wind, Ekman pumping, horizontal divergence of currents and by the propagation of coastally trapped waves. Whereas downwellingalong the coast is driven only by convergence of currents and the propagation of coastally trapped Kelvin waves. Along the west coast of India, the downwelling-favorable Kelvin wavescome from the equator and upwelling-favorable waves come from the Gulf of Mannar region.