West India Coastal Current and Lakshadweep High/Low

Abstract

The West India Coastal Current (WICC) flows northward during November–February and southward during April–September. At the time of formation of the northward (southward) phase of the current, a high (low) in sea level — the Lakshadweep High (Low), forms off southwestern India, and migrates westward across the Arabian Sea. The annual cycle of the WICC and that of the Lakshadweep High/Low arise from a set of circumstances that are special to the North Indian Ocean. This relatively small tropical basin is driven by seasonal monsoon winds. As a result, its wind-driven near-surface circulation consists primarily of annual and semi-annual long, equatorially-trapped Kelvin and Rossby waves, and coastally-trapped Kelvin waves. In terms of these waves, the West India Coastal Current is a superposition of annual and semiannual coastally-trapped Kelvin waves. The Lakshadweep High/Low forms when the Kelvin waves, on turning around Sri Lanka, and propagating northward along the west coast of India, radiate Rossby waves.