We wish to thank NCEP for providing their wind data. We would also like to thank Gary Mitchum for providing the gridded TOPEX/Poseidon and Jason sea level data. We appreciate the comments of the reviewers, which helped to improve the paper significantly. This research is supported by a NASA Jason grant.
Annamalai, H., , and R. Murtugudde, 2004: Role of the Indian Ocean in regional climate variability. Earth’s Climate: The Ocean–Atmosphere Interaction,Meteor. Monogr., Vol. 147, Amer. Geophys. Union, 213–246.
Annamalai, H., , R. Murtugudde, , J. Potemra, , S. P. Xie, , P. Liu, , and B. Wang, 2003: Coupled dynamics over the Indian Ocean: Spring initiation of the zonal mode. Deep-Sea Res. II, 50 , 2305–2330.
Annamalai, H., , S. P. Xie, , J. P. McCreary, , and R. Murtugudde, 2005: Impact of Indian Ocean sea surface temperature on developing El Niño. J. Climate, 18 , 302–319.
Atlas, R., 1997: Atmospheric observations and experiments to assess their usefulness in data assimilation. J. Meteor. Soc. Japan, 75 , 111–130.
Ballabrera-Poy, J., , A. J. Busalacchi, , and R. Murtugudde, 2001: Application of a reduced-order Kalman filter to initialize a coupled atmosphere–ocean model: Impact on the prediction of El Niño. J. Climate, 14 , 1720–1737.
Cane, M. A., , and R. J. Patton, 1984: A numerical model for low-frequency equatorial dynamics. J. Phys. Oceanogr., 14 , 1853–1863.
Chen, D., , L. M. Rothstein, , and A. J. Busalacchi, 1994: A hybrid vertical mixing scheme and its application to tropical ocean models. J. Phys. Oceanogr., 24 , 2156–2179.
Deser, C., , A. S. Phillips, , and J. W. Hurrell, 2004: Pacific interdecadal climate variability: Linkages between the Tropics and the North Pacific during boreal winter since 1900. J. Climate, 17 , 3109–3124.
Fukumori, I., , and P. Malanotte-Rizzoli, 1995: An approximate Kalman filter for ocean data assimilation: An example with an idealized Gulf Stream model. J. Geophys. Res., 100 , 6777–6793.
Gent, P. R., , and M. A. Cane, 1989: A reduced gravity, primitive equation model of the upper equatorial ocean. J. Comput. Phys., 81 , 444–480.
Godfrey, J. S., 1996: The effect of the Indonesian throughflow on ocean circulation and heat exchange with the atmosphere: A review. J. Geophys. Res., 101 , 12217–12237.
Grodsky, S. A., , J. A. Carton, , and R. Murtugudde, 2001: Anomalous surface currents in the tropical Indian Ocean. Geophys. Res. Lett., 28 , 4207–4210.
Hackert, E. C., , R. N. Miller, , and A. J. Busalacchi, 1998: An optimized design for a moored instrument array in the tropical Atlantic Ocean. J. Geophys. Res., 103 , 7491–7509.
Hackert, E. C., , A. J. Busalacchi, , and R. Murtugudde, 2001: A wind comparison study using an ocean general circulation model for the 1997–1998 El Niño. J. Geophys. Res., 106 , 2345–2362.
Halem, M., , E. Kalnay, , W. E. Baker, , and R. Atlas, 1982: An assessment of the FGGE satellite observing system during SOP-1. Bull. Amer. Meteor. Soc., 63 , 407–426.
Hastenrath, S., , A. Nicklis, , and L. Greischar, 1993: Atmospheric–hydrospheric mechanisms of climate anomalies in the western equatorial Indian Ocean. J. Geophys. Res., 98 , 20219–20235.
Hoerling, M. P., , J. W. Hurrell, , T. Xu, , G. T. Bates, , and A. S. Phillips, 2004: Twentieth century North Atlantic climate change. Part II: Understanding the effect of Indian Ocean warming. Climate Dyn., 23 , 391–405.
Huang, R. X., 1993: Real freshwater flux as a natural boundary condition for the salinity balance and thermohaline circulation forced by evaporation and precipitation. J. Phys. Oceanogr., 23 , 2428–2446.
Kaplan, A., , Y. Kushnir, , and M. A. Cane, 2000: Reduced space optimal interpolation of historical marine sea level pressure: 1854–1992. J. Climate, 13 , 2987–3002.
Lagerloef, G. S. E., , G. T. Mitchum, , R. B. Lukas, , and P. P. Niiler, 1999: Tropical Pacific near-surface currents estimated from altimeter, wind, and drifter data. J. Geophys. Res., 104 , 23313–23326.
Levitus, S., , and T. P. Boyer, 1994: Temperature. Vol. 4, World Ocean Atlas 1994, NOAA Atlas NESDIS 4, 117 pp.
Masumoto, Y., , and T. Yamagata, 1996: Seasonal variations of the Indonesian Throughflow in a general ocean circulation model. J. Geophys. Res., 101 , 12287–12293.
McPhaden, M. J., and Coauthors, 1998: The Tropical Ocean Global Atmosphere observing system: A decade of progress. J. Geophys. Res., 103 , 14169–14240.
Miller, R. N., , A. J. Busalacchi, , and E. C. Hackert, 1995: Sea surface topography fields of the tropical Pacific from data assimilation. J. Geophys. Res., 100 , 13389–13425.
Murtugudde, R., , and A. J. Busalacchi, 1999: Interannual variability of the dynamics and thermodynamics of the tropical Indian Ocean. J. Climate, 12 , 2300–2326.
Murtugudde, R., , R. Seager, , and A. Busalacchi, 1996: Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model. J. Climate, 9 , 1795–1815.
Murtugudde, R., , A. J. Busalacchi, , and J. Beauchamp, 1998: Seasonal-to-interannual effects of the Indonesian throughflow on the tropical Indo–Pacific basin. J. Geophys. Res., 103 , 21425–21441.
Murtugudde, R. G., , S. R. Signorini, , J. R. Christian, , A. J. Busalacchi, , C. R. McClain, , and J. Picaut, 1999: Ocean color variability of the tropical Indo-Pacific basin observed by SeaWiFS during 1997–1998. J. Geophys. Res., 104 , 18351–18366.
Murtugudde, R., , J. P. McCreary, , and A. J. Busalacchi, 2000: Oceanic processes associated with anomalous events in the Indian Ocean with relevance to 1997–1998. J. Geophys. Res., 105 , 3295–3306.
Oke, P. R., , and A. Schiller, 2007: A model-based assessment and design of a tropical Indian Ocean mooring array. J. Climate, 20 , 3269–3283.
Perigaud, C., , and P. Delecluse, 1993: Interannual sea level variations in the tropical Indian Ocean from Geosat and shallow water simulations. J. Phys. Oceanogr., 23 , 1916–1934.
Reverdin, G., , D. L. Cadet, , and D. Gutzler, 1986: Interannual displacements of convection and surface circulation over the equatorial Indian Ocean. Quart. J. Roy. Meteor. Soc., 112 , 43–67.
Reynolds, R. W., , and T. M. Smith, 1994: Improved global sea surface temperature analyses using optimum interpolation. J. Climate, 7 , 929–948.
Saji, N. H., , B. N. Goswami, , P. N. Vinayachandran, , and T. Yamagata, 1999: A dipole mode in the tropical Indian Ocean. Nature, 401 , 360–363.
Schiller, A., , S. E. Wijffels, , and G. A. Meyers, 2004: Design requirements for an Argo float array in the Indian Ocean inferred from observing system simulation experiments. J. Atmos. Oceanic Technol., 21 , 1598–1620.
Seager, R., , M. B. Blumenthal, , and Y. Kushnir, 1995: An advective atmospheric mixed layer model for ocean modeling purposes: Global simulation of surface heat fluxes. J. Climate, 8 , 1951–1964.
Sengupta, D., , and M. Ravichandran, 2001: Oscillations of Bay of Bengal sea surface temperature during the 1998 summer monsoon. Geophys. Res. Lett., 28 , 2033–2036.
Servain, J., , A. J. Busalacchi, , M. J. McPhaden, , A. D. Moura, , G. Reverdin, , M. Vianna, , and S. E. Zebiak, 1998: A Pilot Research Moored Array in the Tropical Atlantic (PIRATA). Bull. Amer. Meteor. Soc., 79 , 2019–2031.
Shenoi, S. S. C., , D. Shankar, , and S. R. Shetye, 2002: Differences in heat budgets of the near-surface Arabian Sea and Bay of Bengal: Implications for the summer monsoon. J. Geophys. Res., 107 .3052, doi:10.1029/2000JC000679.
Smith, S. D., 1988: Coefficients for sea surface wind stress, heat flux, and wind profiles as a function of wind speed and temperature. J. Geophys. Res., 93 , 15467–15472.
Smith, T. M., , R. W. Reynolds, , R. E. Livezey, , and D. C. Stokes, 1996: Reconstruction of historical sea surface temperatures using empirical orthogonal functions. J. Climate, 9 , 1403–1420.
Subrahmanyam, B., , I. S. Robinson, , J. R. Blundell, , and P. G. Challenor, 2001: Indian Ocean Rossby waves observed in TOPEX/POSEIDON altimeter data and in model simulations. Int. J. Remote Sens., 22 , 141–167.
Susanto, R. D., , A. L. Gordon, , and Q. N. Zheng, 2001: Upwelling along the coasts of Java and Sumatra and its relation to ENSO. Geophys. Res. Lett., 28 , 1599–1602.
Vecchi, G. A., , and M. J. Harrison, 2007: An observing system simulation experiment for the Indian Ocean. J. Climate, 20 , 3300–3319.
Vossepoel, F. C., , G. Burgers, , and P. J. van Leeuwen, 2002: Effects of correcting salinity with altimeter measurements in an equatorial Pacific Ocean model. J. Geophys. Res., 107 .8001, doi:10.1029/2001JC000816.
Wang, L. P., , C. J. Koblinsky, , and S. Howden, 2001: Annual Rossby wave in the southern Indian Ocean: Why does it “appear” to break down in the middle ocean? J. Phys. Oceanogr., 31 , 54–74.
Webster, P. J., , and S. Yang, 1992: Monsoon and ENSO: Selectively interactive systems. Quart. J. Roy. Meteor. Soc., 118 , 877–926.
Webster, P. J., , V. O. Magana, , T. N. Palmer, , J. Shukla, , R. A. Tomas, , M. Yanai, , and T. Yasunari, 1998: Monsoons: Processes, predictability, and the prospects for prediction. J. Geophys. Res., 103 , 14451–14510.
Webster, P. J., , A. M. Moore, , J. P. Loschnigg, , and R. R. Leben, 1999: Coupled ocean–atmosphere dynamics in the Indian Ocean during 1997–98. Nature, 401 , 356–360.
Wu, R. G., , and B. P. Kirtman, 2004: Understanding the impacts of the Indian Ocean on ENSO variability in a coupled GCM. J. Climate, 17 , 4019–4031.
Xie, P. P., , and P. A. Arkin, 1998: Global monthly precipitation estimates from satellite-observed outgoing longwave radiation. J. Climate, 11 , 137–164.
Xie, S. P., , H. Annamalai, , F. A. Schott, , and J. P. McCreary, 2002: Structure and mechanisms of south Indian Ocean climate variability. J. Climate, 15 , 864–872.
Zhong, A. H., , H. H. Hendon, , and O. Alves, 2005: Indian Ocean variability and its association with ENSO in a global coupled model. J. Climate, 18 , 3634–3649.