THE LARGE-SCALE CONTEXT FOR THE TOGA COUPLED OCEAN-ATMOSPHERE RESPONSE EXPERIMENT

The TOGA Coupled Ocean-Atmosphere Response Experiment (COARE) concentr ated a variety of observational systems in the warm pool of the wester n equatorial Pacific for an Intensive Observation Period (IOP) Novembe r 1992 through February 1993. In this paper, aspects of the large-scal e variations of the tropical atmosphere and Pacific Ocean surrounding the observations of air-sea interaction in the Intensive Flux Array (I FA) during the IOP are described, with the objective of providing a co ntext for the future analyses of these observations. The evolution of the 1991-1999 El Nino/Southern Oscillation event was unusual: Warm SST anomalies in the equatorial cold tongue region switched to colder tha n climatology in the last half of 1992, but waters warmer than 30 degr ees C remained displaced eastward just west of the dateline, continuin g to fuel anomalous convection there during the IOP. Fortunately, SST in the IFA remained warmer than 29 degrees C during most of the IOP, a nd convective activity was observed over the IFA. The Southern Oscilla tion Index, which had relaxed to near zero prior to the experiment, de creased during the IOP, reflecting sea level pressure changes associat ed with renewed westerly wind activity. In response to these westerly wind events, the warm pool migrated back into the central equatorial P acific, leading to a reintensification of the ENSO warm SST anomalies east of the dateline.