ENSO and its relation to the
Kelvin and Rossby Wave
Eric Sinsky
Outline
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Basic El Nino and La Nina dynamics
The basic principles of the Kelvin Wave
The basic principles of the Rossby Wave
The Kelvin wave’s role in ENSO
The Rossby wave’s role in ENSO
An ENSO theory involving Rossby and Kelvin
waves
El Nino
La Nina
How ENSO is quantified
• ENSO is measured in SOI
• Positive values signify La Nina and negative El Nino
1997-1998 El Nino
Thermocline Depth
Kelvin Wave
• Shallow water wave
ℎ
(
λ
<
1
)
20
• Small amplitude (5-10cm)
• Very long wavelength and period
• Non-dispersive
• C= 𝐶𝑔 =
𝑔′ℎ , η(𝑡, 𝑥, 𝑦) = η0 cos(κ 𝑦 − 𝜔𝑡)𝑒
−𝑓𝑥
𝐶
Rossby Wave
•
Deep water wave
ℎ
1
( > )
λ
•
•
•
4
Large amplitude
at thermocline
(~25m)
Very long
wavelength
(500km)
Dispersive
𝜕𝑓
•
𝑐=
−𝜕𝑦
𝑓2
2
κ +𝑔ℎ
Kelvin Wave in ENSO
Rossby Waves in Enso
Comparing Rossby and Kelvin Waves
The Delayed Oscillator
Delayed oscillator applied to 97-98 El Nino
References
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Chelton, D. B., and M. G. Schlax, 1996: Global observations of oceanic
Rossby waves. Science, vol. 272, pp. 234-238.
Knauss, John. Introduction of Physical Oceanography. Long Grove:
Waveland Press, 1997.
Stewart, Robert. Introduction to Physical Oceanography. Texas A&M
University, 2005.
Cipollini, Paolo. Rossby Waves: what are they? University of Southamton,
2000.
Anonymous. A Curious Pacific Wave. National Aeronautics and Space
Administration Science, 2002.
Dijkstra, Henk. Nonlinear Physical Oceanography. New York: SpringerVerlag, 2005.
Laing, Arlene, and Evans, Jenni-Louise. Introduction to Tropical
Meteorology. COMET® Program, 2011.
Harrison, D. E. and G. A. Vecchi (2001), El Niño and La Niña—equatorial
Pacific thermocline depth and sea surface temperature anomalies, 1986–
98, Geophys. Res. Lett., 28(6), 1051–1054, doi:10.1029/1999GL011307.