Abstract
The termination of Indian Ocean Dipole (IOD) events is examined in terms of equatorial wave dynamics. In situ and satellite observations combined with an output from a linear wave model are used in this study. Our emphasis is on the 1997 IOD event but our results apply to other positive IOD events as well. We find that the termination of anomalously cold sea surface temperature (SST) in the eastern pole of the dipole is associated with a warming tendency caused by the net surface heat fluxes. However, net surface heat fluxes alone cannot explain the total change in the SST. We show that during the peak phase of an IOD event, the weakening of zonal heat advection caused by eastern boundary-generated Rossby waves combined with the reduction of vertical entrainment and diffusion creates favorable conditions for surface heat fluxes to warm the SST in the eastern basin.
Highlights
The Indian Ocean Dipole (IOD) is a coupled ocean– atmosphere phenomenon in the tropical Indian Ocean (Saji et al 1999; Webster et al 1999; Murtugudde et al 2000)
We focus on the termination of positive IOD events, with emphasis on the strongest of these in 1997
In this study, we have examined the role of eastern boundary-generated Rossby waves on the termination of the IOD events, with emphasis on the strong 1997 IOD event
Summary
1. Zonal heat advection significantly weakens during the termination phase of theIOD. 2. Weakening of zonal heat advection is due to eastern boundary-generatedRossby waves. 3. Net surface heating more effectively warms the SST as this advective cooling tendency weakens
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