Observed Frontal eddies in the Coastal Bay of Bengal using HF Radar and High-Resolution SST data

Eddies and the fronts are ubiquitous and the major tools to describe the oceanic mesoscale processes. In this study, sub-mesoscale eddies are identified from High Frequency Radar (HFR) (Seasonde, 4.4 MHz) surface current data with a spatial resolution of 6 km in north-western Bay of Bengal (source: INCOIS and NIOT, India). It has been observed that when the western boundary current meanders at around 18N in April 2010, cyclonic eddies developed on the north of main current stream. The formation of those eddies is investigated and are found not due to winds and geostrophic balance from available winds and altimetry data. Higher temperature gradient is generally observed in this region associated with the coastal current which is reversing semi-annually. Therefore, higher resolution sea surface temperature data from MUR-JPL (resolution 1km) has been used identify the fronts in conjunction with those sub-mesoscale eddies to confirm the formation of the frontal eddies. These eddies are found to sustain for about three to four days with variations in their dimensions. The biological production and upwelling characteristics due to cyclonic eddies are being studied.