Understanding ENSO diversity

It has long been known that ENSO events display a broad range of amplitudes, triggers, temporal evolutions, and spatial patterns. However, the recognition that ENSO's impacts, both locally and remotely, can be highly sensitive to these event-to-event differences has been driving a renewed interest in the topic. Due to the atmospheric sensitivity to the detailed structure of equatorial SST anomalies a large emphasis has been placed in characterizing and contrasting events with peak anomalies located in the eastern vs. central Pacific, suggested by some to be distinct modes of tropical Pacific variability. The increased frequency in recent decades of “Central Pacific” El Niños relative to the “canonical” “Eastern Pacific” events has stimulated discussions on whether such a trend may be a manifestation of changes in ENSO character associated with global warming. This presentation will provide a review of our current state of knowledge on ENSO diversity, as emerged from the activity of the US CLIVAR “ENSO diversity” working group, with special emphasis on precursors, impacts, and connection with global warming. Key gaps in understanding and important future research directions will also be highlighted.