Is ENSO a cycle or a series of events? William S. Kessler NOAA / - - PDF document

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Dec 05, 2022 352 likes •460 views

Is ENSO a cycle or a series of events? William S. Kessler NOAA / Pacific Marine Environmental Laboratory, Seattle Early ideas (Wyrtki) saw El Nio as an isolated disturbance. The advent of simple and intermediate coupled models s u

SLIDE 1 Is ENSO a cycle or a series of events? William S. Kessler NOAA / Pacific Marine Environmental Laboratory, Seattle Early ideas (Wyrtki) saw El Nio as an isolated disturbance. The advent

simple and intermediate coupled models s u g g e s t e d a c y c l i c p h e n

e n

, w i t h e a c h phase leading to the next in a self-sustained oscillation. W i l l u s e t h e J i n ( 9 7 ) r e c h a r g e

c i l l a t

a s a paradigm for this type of behavior (the delayed oscillator would do as well). Examine

bserved

ENSO evolution since 1980: Does each phase provide the impetus to advance to the next phase? ( W i l l f i n d a f u n d a m e n t a l a s y m m e t r y a n d b r e a k i n t h e c y c l e ) . The results suggest that El Nios are event-like, requiring a n initiating impulse not contained in the dynamics of the cycle itself.

SLIDE 2 Schematic of the Jin (1997) Recharge-Discharge mode: (After Meinen and McPhaden (2000))

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SLIDE 7 Conclude: Wyrtki was right! (well, not quite ....) O b s e r v a t i

s s u g g e s t t h a t a n E l N i

v e n t l e a v es the system i n a c

s t a t e w i t h s l i g h t l y i n c r e a s e d w a r m w a t e r v

u m e , a n d this state can persist for years, losing memory

conditions. ENSO is not a self-sustained oscillation.

T h e e v

u t i

E N S O s i n c e 1 9 8 a p p e a r s c

s i s t e n t w i t h t h e idea that the basic state is stable

nearly so, and warm events are produced by (stochastic?) forcing external to the cycle itself. All figures from this talk are available at: http://www.pmel.noaa.gov/~kessler/ Latest talk (Kessler, 2002: Geophys. Res. Lett., 29(23), 2125.)

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SLIDE 9 Extra slides .....

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