 Rao et al (2002) and Vinaychadran et al. (2002) are successful in simulating the evolution of the Indian Ocean Dipole events using an ocean general circulation model that is driven by the NCEP fluxes for the period 1975-1998. They are successful in reproducing the positive IOD events of 1997, 1994 and 1982 and negative IOD events during 1996 and 1984-85. They demonstrated that during the positive phase of the IOD easterly wind anomalies excite an upwelling equatorial Kelvin wave. This Kelvin wave reflects from the eastern boundary as an upwelling Rossby wave which propagates westward across the equatorial Indian Ocean. The anomalies in the eastern Indian Ocean weaken after the Rossby wave passes. A similar process excites a downwelling Rossby wave during the negative phase. This Rossby wave is much weaker but wind forcing in the central equatorial Indian Ocean amplifies the downwelling and increases its westward phase speed. This Rossby wave initiates the deepening of thermocline seen in the western Indian Ocean during the following positive phase of the DM. Rossby wave generated in the southern tropical Indian Ocean by Ekman pumping contributes to this warming. Concurrently, the temperature equation of the model shows upwelling and downwelling to be the most important mechanism during both positive events of 1994 and 1997. Rao et al. (2001) further showed that significant subsurface changes in the Indian Ocean occur only during the IOD events and not during the El Niño years contradicting several previous studies. Rao et al. (2001) further showed that the subsurface Indian Ocean helps in reversing the polarity of the surface dipole through propagation of Rossby waves in the off-equatorial regions.
P. N. Vinayachandran, S. Iizuka and T. Yamagata. Indian Ocean Dipole Mode Events in an Ocean General Circulation Model, 2001 Deep Sea Research - II ( pdf) Suryachandra Rao A., S.K.Behera, Y.Masumoto and T.Yamagata. Interannual variability in the subsurface Indian Ocean with a special emphasis on the Indian Ocean Dipole. 2001 Deep Sea Research-II ( pdf)
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