The authors would like to thank the various agencies for providing the different datasets used in this study. Much of the work of the first author was completed while he was a Croucher Foundation Senior Research Fellow and on sabbatical at both the Naval Postgraduate School and the University of Hawaii. The author would like to thank Profs. C. P. Chang, R. L. Elsberry, and B. Wang for supporting his visit to their institutions. Comments from Profs. R. Haney and C. P. Chang improved an earlier version of the manuscript. The suggestion by one of the reviewers, Dr. T. Li, to examine the subsurface ocean structure greatly strengthened the proposed hypothesis.
This research was sponsored by the City University of Hong Kong Grant 9360017. Work of the second author was also partly sponsored by the National Natural Science Foundation of China Grant 49705062.
Barnett, T. P., 1983: Interaction of the monsoon and Pacific trade wind systems at interannual time scales. Part I: The equatorial zone. Mon. Wea. Rev.,111, 756–773.
——, 1984: Interaction of the monsoon and Pacific trade wind system at interannual time scales. Part III: A partial anatomy of the Southern Oscillation. Mon. Wea. Rev.,112, 2388–2400.
——, 1985: Variations in near global sea level pressure. J. Atmos. Sci.,42, 478–501.
Battisti, D. S., 1988: The dynamics and thermodynamics of a warming event in a coupled tropical atmosphere/ocean model. J. Atmos. Sci.,45, 2889–2919.
Bjerknes, J., 1969: Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev.,97, 163–172.
Busalacchi, A., and J. J. O’Brien, 1981: Interannual variability of equatorial Pacific in the 1960’s. J. Geophys. Res.,86, 10 901–10 907.
Cane, M. A., M. Munnich, and S. E. Zebiak, 1990: A study of self-excited oscillations of the tropical ocean–atmosphere system. Part I: Linear analysis. J. Atmos. Sci.,47, 1562–1577.
Gershunov, A., and T. P. Barnett, 1998: Interdecadal modulation of ENSO teleconnections. Bull. Amer. Meteor. Soc.,79, 2715–2725.
Graham, N. E., and W. B. White, 1988:The El Niño cycle: A natural oscillator of the Pacific ocean–atmosphere system. Science,240, 1293–1302.
Gutzler, D. S., and D. E. Harrison, 1987: The structure and evolution of seasonal wind anomalies over the near-equatorial eastern Indian and western Pacific Oceans. Mon. Wea. Rev.,115, 169–192.
Hackert, E. C., and S. Hastenrath, 1986: Mechanisms of Java rainfall anomalies. Mon. Wea. Rev.,114, 745–757.
Hirst, A. C., 1986: Unstable and damped equatorial modes in simple coupled ocean–atmosphere models. J. Atmos. Sci.,43, 606–630.
Lau, K. M., and P. H. Chan, 1985: Aspects of the 40–50 day oscillation during the northern winter as inferred from outgoing longwave radiation. Mon. Wea. Rev.,113, 1889–1909.
——, C.-P. Chang, and P. H. Chan, 1983: Short-term planetary-scale interactions over the Tropics and midlatitudes. Part II: Winter MONEX period. Mon. Wea. Rev.,111, 1372–1388.
Li, T., 1997: Phase transition of the El Niño–Southern Oscillation: A stationary SST mode. J. Atmos. Sci.,54, 2872–2887.
Meehl, G. A., 1987: The annual cycle and interannual variability in the tropical Pacific and Indian Ocean region. Mon. Wea. Rev.,115, 27–50.
Munnich, M., M. A. Cane, and S. E. Zebiak, 1991: A study of self-excited oscillations of the tropical ocean–atmosphere system. Part II: Nonlinear cases. J. Atmos. Sci.,48, 1238–1248.
Philander, S. G., 1983: El Niño–Southern Oscillation phenomena. Nature,302, 295–301.
——, 1985: El Niño and La Niña. J. Atmos. Sci.,42, 2652–2662.
——, and R. C. Pacanowski, 1981: The response of equatorial oceans to periodic forcing. J. Geophys. Res.,86, 1903–1916.
Rasmusson, E. M., and T. H. Carpenter, 1982: Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El-Niño. Mon. Wea. Rev.,110, 354–384.
Reynolds, R. W., and T. M. Smith, 1994: Improved global sea surface temperature analyses using optimum interpolation. J. Climate,7, 929–948.
Suarez, M. J., and P. S. Schopf, 1988: A delayed action oscillator for ENSO. J. Atmos. Sci.,45, 3283–3287.
Wang, B., and Z. Feng, 1996: Chaotic oscillations of tropical climate:A dynamic system theory for ENSO. J. Atmos. Sci.,53, 2786–2802.
——, R. Wu, and R. Lukas, 1999: Roles of the western north Pacific wind variation in thermocline adjustment and ENSO phase transition. J. Meteor. Soc. Japan,77, 1–16.
Wyrtki, K., 1975: El Niño—The dynamic response of the equatorial Pacific Ocean to atmospheric forcing. J. Phys. Oceanogr.,5, 572–584.
Xu, J., and J. C. L. Chan, 2000: The role of the Asian/Australian monsoon system in the onset time of El Niño events. J. Climate, in press.
Yasunari, T., 1985: Zonally propagating modes of the global east–west circulation associated with the Southern Oscillation. J. Meteor. Soc. Japan,63, 1013–1029.
——, 1990: Impact of Indian monsoon on the coupled atmosphere/ocean system in the tropical Pacific. Meteor. Atmos. Phys.,44, 29–41.