This paper benefited from our discussions with Gary Mitchum, Klaus Wyrtki, and Bin Wang and from comments by two anonymous reviewers. We are grateful to Shikiko Nakahara for programming support. TOPEX/Poseidon monthly sea level anomalies were obtained from the NOAA Laboratory for Satellite Altimetry, Reynolds SST monthly data were obtained from the National Meteorological Center, heat storage monthly data were obtained from the Joint Environmental Data Analysis Center at the Scripps Institution of Oceanography, and wind data were obtained from The Florida State University’s Center for Ocean–Atmospheric Prediction Studies. This research was supported by the Office of Global Programs, NOAA Grant NA67RJ0154.
Cheney, B., L. Miller, R. Agreen, N. Doyle, and J. Lillibridge, 1994:TOPEX/POSEIDON: The 2-cm solution. J. Geophys. Res.,99, 24 555–24 564.
Delcroix, T., and J. Picaut, 1998: Zonal displacements of the western equatorial Pacific fresh pool. J. Geophys. Res.,103, 1087–1098.
——, J.-P. Boulanger, F. Masia, and C. Menkes, 1994: Geosat-derived sea level and surface current anomalies in the equatorial Pacific during the 1986–1989 El Niño and La Niña. J. Geophys. Res.,99, 25 093–25 107.
Frankignoul, C., F. Bonjean, and G. Reverdin, 1996: Interannual variability of surface currents in the tropical Pacific during 1987–1993. J. Geophys. Res.,101, 3629–3647.
Goldenberg, S. B., and J. J. O’Brien, 1981: Time and space variability of tropical Pacific wind stress. Mon. Wea. Rev.,109, 1190–1207.
Graham, N. E., and W. B. White, 1991: Comments on “On the Role of Off-equatorial Oceanic Rossby Waves during ENSO”. J. Phys. Oceanogr.,21, 453–460.
Ji, M., A. Leetmaa, and J. Derber, 1995: An ocean analysis system for seasonal to interannual climate studies. Mon. Wea. Rev.,123, 460–481.
Kessler, W. S., 1990: Observations of long Rossby waves in the northern tropical Pacific. J. Geophys. Res.,95, 5183–5217.
——, 1991: Can reflected extra-equatorial Rossby waves drive ENSO? J. Phys. Oceanogr.,21, 444–452.
——, and B. A. Taft, 1987: Dynamic heights and zonal geostrophic transports in the central tropical Pacific during 1979–84. J. Phys. Oceanogr.,17, 97–122.
——, and M. J. McPhaden, 1995: The 1991–1993 El Niño in the central Pacific. Deep-Sea Res.,42, 295–333.
Kilonsky, B. J., and P. Caldwell, 1991: In the pursuit of high-quality sea level data. IEEE Oceans Proc.,2, 669–675.
Latif, M., and M. Flügel, 1991: An investigation of short-range climate predictability in the tropical Pacific. J. Geophys. Res.,96, 2661–2673.
McPhaden, M. J., and Coauthors, 1998: The Tropical Ocean–Global Atmosphere observing system: A decade of progress. J. Geophys. Res.,103, 14 169–14 240.
Meyers, G., and J.-R. Donguy, 1984: The North Equatorial Countercurrent and heat storage in the western Pacific Ocean during 1982–83. Nature,312, 258–260.
Mitchum, G. T., 1993: Principal component analysis: Basic methods and extensions. Aha Hulioko’a: Statistical Methods in Oceanography, P. Müller and D. Henderson, Eds., SOEST Publication Services, 185–199.
Picaut, J., and T. Delcroix, 1995: Equatorial wave sequence associated with warm pool displacements during the 1986–1989 El Niño–La Niña. J. Geophys. Res.,100, 18 393–18 408.
Rébert, J.-P., J. R. Donguy, G. Eldin, and K. Wyrtki, 1985: Relations between sea level, thermocline depth, heat content, and dynamic height in the tropical Pacific Ocean. J. Geophys. Res.,90, 11 719–11 725.
Reynolds, R. W., and D. C. Marisco, 1993: An improved real-time global sea surface temperature analysis. J. Climate,6, 114–119.
Smith, W. H. F., and P. Wessel, 1990: Gridding with continuous curvature splines in tension. Geophysics,55, 293–305.
Taft, B. A., and W. S. Kessler, 1991: Variations of zonal currents in the central tropical Pacific during 1970 to 1987: Sea level and dynamic height measurements. J. Geophys. Res.,96, 12 599–12 618.
Tourre, Y. M., and W. B. White, 1995: ENSO signals in global upper-ocean temperature. J. Phys. Oceanogr.,25, 1317–1332.
Wang, B., 1995: Interdecadal changes in El Niño onset in the last four decades. J. Climate,8, 267–285.
Wessel, P., and W. H. F. Smith, 1995: New version of the generic mapping tools released. Eos, Trans. Amer. Geophys. Union,76, 329.
White, W. B., 1994: Slow El Niño–Southern Oscillation boundary waves. J. Geophys. Res.,99, 22 737–22 751.
Wyrtki, K., 1974a: Equatorial currents in the Pacific 1950 to 1970 and their relations to the trade winds. J. Phys. Oceanogr.,4, 372–380.
——, 1974b: Sea level and the seasonal fluctuations of the equatorial currents in the western Pacific Ocean. J. Phys. Oceanogr.,4, 91–103.
——, 1977: Sea level during the 1972 El Niño. J. Phys. Oceanogr.,7, 779–787.
——, 1979: The response of sea surface topogrphy to the 1976 El Niño. J. Phys. Oceanogr.,9, 1223–1231.
——, 1985: Water displacements in the Pacific and genesis of El Niño cycles. J. Geophys. Res.,90, 7129–7132.
——, and J. Wenzel, 1984: Possible gyre–gyre interaction in the Pacific Ocean. Nature,309, 538–540.
Zhang, R.-H., and S. Levitus, 1996: Structure and evolution of interannual variability of the tropical Pacific upper ocean temperature. J. Geophys. Res.,101, 20 501–20 524.
——, and ——, 1997: Interannual variability of the coupled tropical Pacific Ocean–atmosphere system associated with the El Niño–Southern Oscillation. J. Climate,10, 1312–1330.