When atmosphere met ocean: perspectives on ENSO interactions

Eugene Rasmusson and collaborators defined many of the observational targets for surface and atmospheric observations of El Niño/Southern oscillation (ENSO) that modelers strove to simulate and explain. Klaus Wyrtki's contributions included pointing toward the role of subsurface oceanic evolution and Western Pacific mass balance in ENSO evolution, which has turned out to underpin much of the predictability of ENSO. Elements of their work will be used as a jumping off point to review some of what we have learned about the system, beginning with the remarkably productive years surrounding the decade of the Tropical-Ocean-Global-Atmospheric experiment — including the role of theoretical and modeling predictions for unobserved subsurface aspects of the phenomenon in the conception of the subsequent observational network. Rasmusson and Wyrtki's contributions are emblematic of the atmospheric and oceanic aspects that were drawn together in the ENSO problem, and connect to a sampling of current issues and challenges, including the teleconnection problem.