The Eugene Rasmusson Symposium


The robust lifecycles and seasonal impacts of El Niņo and La Nina events

Narasimhan K. ("Sim") Larkin, USDA Forest Service, Seattle, WA; and D. E. Harrison

Rasmusson and Carpenter (1982), through their six event composites over the tropical Pacific, launched the modern study of El Niņo events. Utilizing modern marine surface datasets, we have built on Rasmusson and Carpenter (1982), expanding the composite perspective with statistical significance and time series techniques and including more recent El Niņos, global anomalies, and La Nina events. We have identified the robust lifecycle elements of ENSO and the robust associated seasonal weather anomalies.

Intrinsic to any such study is a definition of El Niņo and La Nina. Appropriately defined, El Niņo and La Nina have robust lifecycles that span at least nine months, include anomalies in every tropical ocean and in the extra-tropics, and differ substantially from simple regression patterns. The extreme 1997-98 El Niņo, apart from its amplitude, followed the typical tropical life cycle quite well. Many of the most robust life cycle elements are found in the central and eastern tropical Pacific; a focus on conditions there, rather than nearer the Dateline (e.g., NINO3.4), is what permits the robust composite events to be constructed.

Poster Session 1, Poster Session
Thursday, 18 January 2007, 9:45 AM-11:00 AM, Exhibit Hall C

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