Spatial Distribution of Upwelling off the Central East Coast of India

Abstract

The spatial distribution of upwelling along the central east coast of India (13°–18°N) in the premonsoon and south-west monsoon seasons is described using data collected during cruises 193 (13–28 March 1988) and 200 (23 August– 7 September 1988) of R. V. Gaveshani. Five hydrographic sections were covered during both the seasons and were examined for response to meteorological forcing. Differing scales and intensities in coastal upwelling were documented through the analysis of the data collected along the five sections. At all the sections, a decrease in water temperature and an increase in salinity from the offshore stations to the stations closest to the shore indicated coastal upwelling. The Rossby radii of deformation indicated that the influence of the upwelled water can be seen up to a distance of 28 to 53km from the coast along the sections during the premonsoon season and to a distance of 35 to 46km during the southwest monsoon season. The upwelling area centred off Visakhapatnam was found to be of greater spatial extent than the other upwelling areas associated with the other sections located further south. Variations in the intensity of alongshore wind velocity affected the structure and intensity of upwelling off the central east coast of India.