16.15
Putting the 1997–98 El Nino in historical perspective
N. K. Larkin, JISAO/Univ. of Washington, Seattle, WA; and D. E. Harrison
We place the 1997-98 El Nino in a historical framework using recent work on the global statistically significant ocean surface anomalies that occured during the post-WWII El Nino events. By comparing the 1997-98 event with the results of a historical Robust Composite of those features typical of all El Ninos, and through event by event comparison, we find that the 1997-98 event was the strongest event since 82-83 by most indices, and had equatorial Pacific Cold Tongue anomalies that peaked at more than 3 standard deviations in SST, SLP and zonal wind. The time and space evolution of the anomalies within the Cold Tongue followed the historical Composite patterns patterns in many respects. The precursive zonal wind anomalies in the eastern equatorial Indian ocean, and the existence of warm Indian SST anomalies during much of the event also were very like those of the Composite. Outside of the tropics the anomalies differed from the composite in many ways, and agreed with it in a few. The very warm waters along the west coast of the Americas, which ultimately extended across to Kamchatka, were very different from typical behavior.
Thus the 97-98 El Nino event followed the Robust Composite El Nino quite well in the global tropical band. In fact, the Robust features of the El Nino Composite were generally present during this event over the global ocean. But the smaller amplitude statistically significant features of the Composite were not particularly skillful at capturing the extra-tropical features of this major El Nino event.
Session 16, Interannual Variability III: Observational Studies
Thursday, 17 January 2002, 10:30 AM-3:30 PM
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