Link Between Equatorial Wind Anomalies and Intraseasonal Eddies in the Northeastern Bay of Bengal

Abstract

AbstractFeatures and mechanism of intraseasonal cyclonic and anticyclonic eddy generation in the northeastern Bay of Bengal (NE‐BoB) are investigated using satellite observations, ocean reanalysis, and related wind forcing data. Our results suggest that the intraseasonal cyclonic (anticyclonic) eddies generated in the NE‐BoB can be primarily attributed to intraseasonal easterly (westerly) wind anomalies in the equatorial Indian Ocean, which provokes the upwelling (downwelling) Kelvin wave (KW) traveling along the equator and subsequently the eastern boundary through the Preparis Channel into the NE‐BoB. Anomalous equatorial zonal wind can result in a strong intraseasonal subsurface flow along the KW waveguide located on the continental slope, and this KW‐associated subsurface flow is essential to the formation process of both anticyclonic and cyclonic eddies in the NE‐BoB. A seasonal difference in the response of sea level anomaly (SLA) to the KW‐associated subsurface flow is revealed, which can be explained by the seasonal variability of stratification along the waveguide. The eddy related SLA shows a considerable correlation coefficient of −0.58 with the accumulated transport caused by KW‐associated subsurface flows through the Preparis Channel when it lags 18 days, indicating a possible eddy generation mechanism that the KW‐associated subsurface flow dominated net horizontal inflow (outflow) causes vertical stretching (shrinking) of the subsurface layer, which in turn triggers an anticyclonic (cyclonic) eddy.