The Role of Equatorial Oceanic Waves in the Activation of the 2006 Indian Ocean Dipole


  • Iskhaq Iskandar 1Jurusan Fisika, Fakultas MIPA, Universitas Sriwijaya Kampus Inderalaya, Jln. Raya Palembang-Prabumulih Km. 32 Indralaya, Ogan Ilir, Sumatra Selatan 30662, Indonesia 2Pusat Study Geohazard dan Perubahan Iklim, Fakultas MIPA, Universitas Sriwijaya, Jln. Raya Palembang-Prabumulih Km. 32 Indralaya, Ogan Ilir, Sumatra Selatan 30662, Indonesia



Observations and a linear wave model were used to evaluate the role of equatorial oceanic wave processes in affecting the evolution of the 2006 positive Indian Ocean Dipole (IOD), focusing on the activation phase of the event. The observations indicate the presence of upwelling equatorial waves and westward near-surface zonal currents along the equator during the activation phase of the event in August 2006. These upwelling equatorial waves (negative sea surface height anomalies) and westward zonal current anomalies contributed to significant sea surface cooling in the eastern equatorial Indian Ocean. The model results reveal that the upwelling equatorial waves and westward nearsurface zonal currents were mainly generated by wind-forced Kelvin waves associated with the easterly wind anomalies. On the other hand, anomalous easterly winds along the equator during June caused downwelling waves (positive sea surface height anomalies) in the off-equatorial region which propagated westward and elevated sea levels in the western region. The model further shows that a complex interplay of wind-forced and boundary-generated Rossby waves elevated sea levels in the western equatorial Indian Ocean during the activations phase of the 2006 IOD event.


Saji, N.H., Goswami, B.N., Vinayachandran, P.N. & Yamagata, T., ADipole Mode in the Tropical Indian Ocean, Nature, 410, pp. 360-363,1999.

Webster, P.J., Moore, A.W., Loschnigg, J.P. & Leben, R.R., Coupled Ocean-Atmosphere Dynamics in the Indian Ocean during 1997-98, Nature, 401, pp. 356-360, 1999.

Murtugudde, R., McCreary, J.P. & Busalacchi, A.J. Oceanic Processes Associated with Anomalous Events in the Indian Ocean with Relevance to 1997-98, J. Geophys. Res., 105(C2), pp. 3295-3306, 2000.

Saji, N.H., & Yamagata, T. Possible Impacts of Indian Ocean Dipole Mode Events on Global Climate, Clim. Res., 25(2), pp. 151-169, 2003.

Horii, T., Hase, H., Ueki, I. & Masumoto, Y., Oceanic Precondition and Evolution of the 2006 Indian Ocean Dipole, Geophys. Res. Lett., 35, L03607, doi: 10.1029/2007GL032464, 2008.

Vinayachandran, P.N., Kurian, J. & Neema, C.P., Indian Ocean Response to Anomalous Conditions in 2006, Geophys. Res. Lett., 34, L15602, doi: 10.1029/2007GL030194, 2007.

Rao, S.A., Luo, J.-J., Behera, S.K. & Yamagata, T., Generation and Termination of Indian Ocean Dipole Events in 2003, 2006 and 2007, Clim. Dyn., 33, pp. 751-767, doi: 10.1007/s00382-008-0498-z, 2009.

Cai, W., Pan, A., Roemmich, D., Cowan, T. & Guo, X., Argo Profiles a Rare Occurrence of Three Consecutive Positive Indian Ocean Dipole Events, 2006-2008, Geophys. Res. Lett., 36, L08701, doi: 10.1029/2008GL037038, 2009.

Bonjean, F. & Lagerloef, G.S.E., Diagnostic Model and Analysis of the Surface Currents in the Tropical Pacific Ocean, J. Phys. Oceanogr., 32, pp. 2938-2954, 2002.

Nagura, M. & Mcphaden, M.J., Wyrtki Jet Dynamics: Seasonal Variability, J. Geophys. Res., 115, C07009, doi: 10.1029/2009JC005922, 2010.

Nagura, M. & Mcphaden, M.J., The Dynamics of Zonal Current Variations Associated with the Indian Ocean Dipole, J. Geophys. Res., 115, C11026, doi: 10.1029/2010JC006423, 2010.

Clarke, A. J. & Liu, X., Observations and Dynamics of Semiannual and Annual Sea Level near the Eastern Equatorial Indian Ocean Boundary, J. Phys. Oceanogr., 23, pp. 386-399, 1993.

Han, W., Origins and Dynamics of the 90-day and 30-60-day Variations in the Equatorial Indian Ocean, J. Phys. Oceanogr., 35, pp. 708-728, 2005.

Le Blanc, J.L. & Boulanger, J.P., Propagation and Reflection of Long Equatorial Waves in the Indian Ocean from Topex/Poseidon Data during 1993-1998, Climate Dynamics, 17, pp. 547-557, 2001.

Chambers, D.P., Tapley, B.D. & Stewart, R.H., Amomalous Warming in the Indian Ocean Coincident with El Nino., J. Geophys. Res. 104, pp. 3035-3047, doi: 10.1029/1998JC900085, 1999.

Rao, S.A., Behera, S.K., Masumoto, Y. & Yamagata, T., Interannual Subsurface Variability in the Tropical Indian Ocean with a Special Emphasis on the Indian Ocean Dipole, Deep-Sea Res., 49, pp.1549-1572, 2002.

Feng, M. & Meyers, G., Interannual Variability in the Tropical Indian Ocean: a Two-year Time-scale of Indian Ocean Dipole, Deep-Sea Res.,50, pp. 2263-2284, 2003.

Horii, T., Masumoto, Y., Ueki, I., Hase, H. & Mizuno, K., Mixed Layer Temperature Balance in the Eastern Indian Ocean during the 2006 Indian Ocean Dipole, J. Geophys. Res., 114, C07011, doi: 10.1029/2008JC00 5180, 2009.