Simulated Interannual Modulation of Intraseasonal Kelvin Waves in the Equatorial Indian Ocean

Iskhaq Iskandar, Dedi Setiabudidaya, Wijaya Mardiansyah, Muhammad Irfan


Outputs from a high-resolution ocean general circulation model (OGCM) for the period of 1990-2003 indicate an interannual modulation of intraseasonal Kelvin waves along the equatorial Indian Ocean. During normal conditions without IOD event, the first mode explains about 30-40% of the total variance in the western (60-65ºE) and central (75-80ºE) basin, while the second mode contributes up to 45% to the total variance in the central basin around the longitude of 82ºE. In contrast, during the 1997/98 IOD event, the fourth mode caused about 40% of the total variance in the central and eastern basin. During the 1994 IOD event, the contribution from the fourth baroclinic mode in the eastern basin caused 45% of the total variance. In the central basin, the second and the fourth baroclinic mode caused almost the same variance (~40%). The variations in the characteristics of the intraseasonal Kelvin waves are related to variations in the vertical stratification. During the IOD event, the pycnocline in the eastern basin was raised by about 50 m and the stratification at the upper level is strengthened, while it is weakened at lower levels. These changes lead to an increase in the contribution of higher-order baroclinic modes.


Indian Ocean Dipole; interannual modulation; intraseasonal Kelvin waves; ocean general circulation model; vertical baroclinic mode.

Full Text:



Wyrtki, K., An Equatorial Jet in the Indian Ocean, Science, 181(4096), pp. 262-264, 1973.

Iskandar, I., Masumoto, Y., Mizuno, K., Sasaki, H., Affandi, A.K., Setiabudidaya, D. & Syamsuddin, F., Coherent Intraseasonal Oceanic Variations in the Eastern Equatorial Indian Ocean and in the Lombok and Ombai Straits from Observations and a High-Resolution OGCM, J. Geophysical Research, 119(2), pp. 615-630, 2014. doi:10.1002/ 2013JC009592

Iskandar, I., Mardiansyah, W., Masumoto, Y. & Yamagata, T., Intraseasonal Kelvin Waves Along the Southern Coast of Sumatra and Java, J. Geophysical Research, 110(C04013), 2005. doi:10.1029/2004JC 002508

Iskandar, I. & McPhaden, M.J., Dynamics of Wind-forced Intraseasonal Zonal Current Variations in the Equatorial Indian Ocean, J. Geophysical Research, 116(C06019), 2011. doi:10.1029/ 2010JC006864

Nagura, M. & McPhaden, M.J., The Dynamics of Wind-driven Intraseasonal Variability in the Equatorial Indian Ocean, J. Geophysical Research, 117(C02001), 2012. doi:10.1029/2011JC007405

Rao, S.A. & Yamagata, T., Abrupt Termination of Indian Ocean Dipole Events in Response to Intraseasonal Disturbances, Geophysical Res. Letter, 31(L19306), 2004. doi:10.1029/2004GL020842

Han, W., Shinoda, T., Fu, L-L. & McCreary, J.P., Impact of Atmospheric Intraseasonal Oscillations on the Indian Ocean Dipole during the 1990s, J. Physical Oceanography, 36, pp. 670-690, 2006.

Saji, N.H., Goswami, B.N., Vinayachandran, P.N. & Yamagata, T., A Dipole Mode in the Tropical Indian Ocean, Nature, 401, pp. 360-363, 1999.

Vinayachandran, P.N., Saji, N.H. & Yamagata, T., Response of the Equatorial Indian Ocean to An Unusual Wind Event during 1994, Geophysical Res. Letter, 26(11), pp. 1613-1616, 1999.

Murtugudde, R., McCreary, J.P. & Busalacchi, A.J., Oceanic Processes Associated with Anomalous Events in the Indian Ocean with Relevance to 1997-1998, J. Geophysical Research, 105(C2), pp. 3295-3306, 2000.

Dewitte, B., Reverdin, G. & Maes, C., Vertical Structure of an OGCM Simulation of the Equatorial Pacific Ocean in 1985-94, J. Physical Oceanography, 29, pp. 1542-1570, 1999.

Iskandar, I., Tozuka, T., Masumoto, Y., & Yamagata, T., Impact of Indian Ocean Dipole on Intraseasonal Zonal Currents at 90ºE on the Equator as Revealed by Self-organizing Map, Geophysical Res. Letter, 35(L14S03), 2008. doi:10.1029/2008GL033468

Luo, J-J., Masson, S., Behera, S.K. & Yamagata, T., Experimental Forecasts of Indian Ocean Dipole using a Coupled OAGCM, J. Climate, 20, pp. 2178-2190, 2007.

Gill, A.E. & Clarke, A.J., Wind-induced Upwelling, Coastal Currents and Sea-level Changes, Deep-Sea Research, 21(5), pp. 325-345, 1974.

Kumar, B.P., Vialard, J., Lengaigne, M., Murty, V.S.N. & McPhaden, M.J., TropFlux: Air-sea Fluxes for the Global Tropical Oceans–Description and Evaluation Against Observations, Clim. Dyn., 38(7), pp. 1521-1543, 2012. doi:10.1007/s00382-011-1115-0

Masumoto, Y., Sasaki, H., Kagimoto, T. Komori, N., Ishida, A. Sasai, Y. Miyama, T., Motoi, T., Mitsudera, H., Takahashi, K., Sakuma, H. & Yamagata, T., A Fifty-year Eddy-resolving Simulation of the World Ocean–Preliminary Outcomes of OFES (OGCM for the Earth Simulator), J. Earth Simulator, 1, pp. 35-56, 2004.

Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Leetmaa, A., Reynolds, R., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K.C., Ropelewski, C., Wang, J., Jenne, R. & Joseph, D., The NCEP/NCAR 40-Year Reanalysis Project, Bulletin American Meteor. Soc., 77, pp. 437-471, 1996. doi: 10.1175/1520-0477(1996)077<0437: TNYRP>2.0.CO;2

Hosoda, S., Suga, T., Shikama, N. & Mizuno, K., Global Surface Layer Salinity Change Detected by Argo and Its Implication for Hydrological Cycle Intensification, J. Oceanography, 65, pp. 579-586, 2009.

McPhaden, M.J., Proehl, J.A. & Rothstein, L.M., The Interaction of Equatorial Kelvin Waves with Realistically Sheared Zonal Currents, J. Physical Oceanography, 17, pp. 1499-1515, 1986.



  • There are currently no refbacks.

View my Stats

Creative Commons License
This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.