Seasonally reversing current bands across 15° N in the Arabian Sea and their implications

Abstract

Geostrophic currents computed from hydrographic data collected in different months from a section along 15-degrees-N in the Arabian Sea show alternate N-S current bands. Flow directions of these bands are found to reverse with the change in season. Analysis of ship drift data (KNMI atlas) supports the existence of such bands in this area. Evidences suggest the possibility that these current bands can be due to westward propagation of planetary (Rossby) waves of annual periodicity with a probable speed of 1-2 cm.sec-1 and wave length varying between 200 and 500 km. Generation of these waves is thought to be linked to the SW and NE monsoon winds in this region.