In 1982, when the need for focussed ENSO studies was just being discussed, the strongest warm phase of ENSO of this century was developing in the Pacific Ocean without the scientific community being in the least aware of it. The destructive impacts of the huge 1982/3 warm event in the Pacific were felt as far away as coastal North America and resulted in disaster declarations by the Governors of California, Oregon, and Washington. It was subsequently realized that a fundamental requirement for all future ENSO studies was a capability to observe the surface and near surface of the tropical Pacific in real time. The last four years have seen that capability reach fruition.
The oceanic component of the TOGA Observing System consists of expendable bathythermograph (XBT) observations from Voluntary Observing Ships (VOS), a sea-level network, a drifter array which measures sea surface temperature (SST) and position, and the TOGA Tropical Atmosphere/Ocean (TAO) Array [ Hayes et al., 1991], all telemetering in real time to the Global Telecommunication System, from which the data is available for research and prediction purposes (see National Research Council [1994] for a complete discussion).
As a result of the TOGA Observing System, we can now observe the state of the upper tropical Pacific Ocean in real time; we are developing accurate climatologies of upper ocean thermal structure, surface winds, and upper ocean currents; we have developed assimilation techniques so that fields of data for the entire tropical Pacific are continuously available [ Leetmaa and Ji, 1989]; we are gradually coming to understand the nature of the annual, interannual, and longer term variability of the Pacific; and we use the surface data routinely for operational weather forecasting and the surface and subsurface data for experimental short term (i.e., seasons to a year) climate forecasting. Monthly summaries of the observations are available in the Climate Diagnostics Bulletin where instructions for access to the data over Internet (via ftp) are also given.
While the TOGA Observing System is itself an extraordinary achievement, the intimate interplay between observations and predictions that has developed during TOGA makes the study of ENSO variability and predictability particularly exciting and fruitful.