1. GEOS 513 ENSO: Past, Present, Future
Michael N. Evans
Laboratory of Tree-Ring Research/Geosciences/Atmospheric Sciences
course web pages:
January 18, 2006:
References
M.A. Cane, Oceanographic events during El Nino, Science 222(4629): (1983);
E.M. Rasmussen and J.M. Wallace, Meteorological aspects of the El Nino/Southern Oscillation, Science 222(4629): (1983).
1. The equatorial Pacific: mean state, annual cycle, and ENSO
2. How was the event similar to the canonical ENSO event?
3. How was the event unusual (is it still considered unusual?)

2. Coupled ocean-atmosphere system
(With apologies to the graphically-enabled)

3. Ekman effects (Pond and Pickard, 1989)

4. Annual cycle in sea surface temperature
180
100W
(Cane, 1983)

5. Annual cycle: outgoing longwave radiation (OLR)

6. Canonical ENSO warm phase event (Cane, 1983)

7. Kelvin wave theory (Holton, 1992)

8. Rossby wave theory (Holton, 1992)
absolute
Rossby wave theory (Holton, 1992)

9. Canonical oceanographic ENSO (Cane, 1983)

10. Canonical ENSO teleconnection pattern (Rasmussen and Wallace, 1983)

11. Coupled ocean-atmosphere system
(With apologies to the graphically-enabled)

12. Canonical ENSO oceanographic indicators

13. Canonical ENSO atmospheric indicators

14. How was the 1982-3 ENSO warm phase event typical? What made it special?

15. 1982-3 ENSO warm phase event Kelvin wave

16. 1982-3 event character (Cane, 1983)

17. 1982-3 ENSO warm phase event OLR anomaly (Rasmussen and Wallace, 1983)

18. Canonical vs. 1982-3 ENSO warm phase teleconnection anomaly
(Rasmussen and Wallace, 1983)

19. How was the 1982-3 event similar to the canonical event?
Largely explained by equatorial (Kelvin) wave theory (oceans)
Largely explained by midlatitude (Rossby) wave theory (atmosphere)
A superposition of
Coastal, annual-cycle-like anomalies
Central equatorial Pacific-centered anomalies

20. How was the 1982-3 event different from the canonical event?
Anomaly propagation: west to east across central- eastern equatorial Pacific
Reversal of trade winds in central equatorial Pacific
Disappearance of Equatorial Undercurrent
Reversed event timing (or else, near-simultaneous coastal and open-ocean ENSO anomalies)
Large amplitude, long duration

21. Was the 1997-8 El Nino event the second 'El Nino of the Century'?
Source: Climate Analysis Center SST anomaly product (

22. Summary
ENSO events can be described as an amplification of the annual cycle of the couplued tropical Pacific ocean- atmosphere system.
The event was largely consistent with Kelvin and Rossby wave theory
...But it was unusual in terms of
Timing
Amplitude
Anomaly propagation
Severity of teleconnections
Until the event appeared.