Mesoscale eddy variability and its linkage to deep convection over the Bay of Bengal using satellite altimetric observations

Abstract

In the Bay of Bengal (BoB), surface circulation is strongly influenced by the Indian Monsoon and notable local eddying that modulates the East India Coastal Current (EICC). In this study, we apply an eddy tracking algorithm to 25 years (1993–2018) of satellite altimetric observations to identify, analyze, and track mesoscale eddies in the BoB from their generation to dissipation. We compare the characteristics and trajectories of these eddies during the southwest (SW) and northeast (NE) monsoon seasons and during the pre- and post-SW monsoon periods to better understand the seasonality of the local eddy field. We find high eddy generation in the eastern BoB associated with instability induced by coastal Kelvin waves and the westward propagating Rossby waves, but we found the most robust eddies in the western BoB around the EICC. Ocean heat content (OHC) in the BoB was compared with warm-core eddies and we find that warm-core eddies drive changes in OHC. We also compared the eddy field during strong and weak SW monsoon forcing and with varying Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) conditions, finding a statistically significant relationship with warm-core eddies and sea surface temperatures (SSTs; R2 = 91%) and outgoing longwave radiation (OLR; R2 = 88%) during periods of strong ENSO and IOD forcing. To understand the impact of these eddies on local atmospheric convection we found the composite surface structure of anticyclonic and cyclonic eddies of warm-core and cold-core SSTs, finding a close relationship between the eddy-composite SSTs and OLR.