Seasonal and inter-annual variability of surface circulation in the Bay of Bengal from TOPEX/Poseidon altimetry

Sea-surface height anomalies (SSHA) from TOPEX/Poseidon altimeter from January 1993 to December 1997 have been analyzed to document the seasonal, intra-seasonal and inter-annual variability of surface circulation in the Bay of Bengal. The western bay between 12° and 16°N exhibited large variability on all time scales. A strong cyclonic gyre prevailed in this region from autumn through winter season and was replaced by an anticyclonic gyre in spring. In 1993 and 1997, the intense winter cyclonic gyre was embedded as cyclonic eddy between two anticyclonic cells in the following spring. During summer (southwest monsoon period), alternate cyclonic and anticyclonic circulation cells prevailed in the western bay. On inter-annual time scales, the surface circulation of the bay was closely linked to the El Niٌo Southern Oscillation (ENSO) and the bay circulation responded to all the phases of ENSO events. The SSHA and the sea-surface temperature anomaly (SSTA) off Sumatra and in the bay were negatively correlated to the SSTA in the Western Equatorial Pacific both during El Niٌo and La Niٌa. The coastal trapped Kelvin waves and radiated Rossby waves provide the oceanic link between the equatorial region and the bay for the observed variability in SSHA.