The large-scale structure and variability described in this paper provoke many questions that will be addressed in diagnostic studies, some of which are already in progress by many COARE investigators. Some of these issues can be listed as part of a brief overview of the results we have presented.
It is very difficult to characterize the lingering warm episode-like conditions on terms of current paradigms for ENSO, although other multi-year warm events can be identified in the historical record. The COARE data will augment long-term datasets for studies aimed at understanding the persistence and rejuvenation of significant warm conditions near the date line in 1992-1993. The role of high-frequency fluctuations (intraseasonal oscillations and the higher-frequency wind bursts embedded within them) in maintaining the SST anomalies could prove to be a particularly interesting avenue for further research.
The upper-tropospheric circulation across the tropical Pscific in DJF was strongly disturbed by the near-equatorial convective anomalies, though not in the usual way, as shown by the 200-mb circulation anomalies in Fig. 7. Obtaining a better understanding of the far-field effects of warm-pool convection is one of the primary science goals of COARE, so it is fortunate that the IOP occurred during such and interestingly perturbed season.
Intraseasonal variability was quite pronounced during the IOP, offering excellent examples of intraseasonal Madden-Julian oscillations for detailed study. As shown in Fig. 9, there seem to be significant ocean-atmosphere interactions associated with these oscillations, although much work needs to be done to describe and understand the full scope of the interactions. The intraseasonal oscillations represent an intermediate-scale phenomenon, affecting and being affected by the lower freqeuncy ENSO-related evolution of the coupled system, and modulating higher frequency fluctuations of organized convection and circulation. The COARE dataset offers a unique resource for examination of these scale interactions.
After the COARE IOP, however, the extremely regular propagation and recurrence of intraseasonal oscillations became less pronounced. The CEPEX period immediately following the IOP represented a regime of weaker intraseasonal activity and more stationary convection over areas of warmest SST. Studies of the contrast between the COARE IOP and CEPEX observation periods should provide interesting insights into the suite of air-sea interactions that occurs across the tropical western Pacific. These interactions are of crucial importance for understanding present-day climate variability and possible future climate change.