ENSO and ITF

Mao-Lin Shen

October 26, 2010

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 2

Bjerknes Feedback Dommenget, D. (2010), The slab ocean El Niño,

Geophys. Res. Lett., 37(20), L20701. Santoso et al. (2010), The role of the Indonesian

Throughflow on ENSO dynamics in a coupled climate model, J. Climate (revised).

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 3

Oceanic Thermocline

Tropical Atmosphere Ocean (TAO) Buoy Array (since ~1983)

0 m

200 m

400 m

Dep

th

T (z)Oct 2007

wind

thermocline

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 4

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 5

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

“Bjerknes Feedback”

positive SST anomaly

negative SLP anomaly

westerly wind anomaly

deepened thermocline

positive SST anomaly

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 6

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedbackPoleward Vg

anomaly L H V ~ dp/dx

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 7

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

Neutral State

ShallowerMeanThermocline

Poleward Vg

anomaly L H V ~ dp/dx

Ocean Heat Discharge

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 8

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

Neutral State

ShallowerMeanThermocline

Poleward Vg

anomaly L H V ~ dp/dx

Ocean Heat DischargeShallow thermocline >Cold SST via upwelling

Cold event

Positive feedback

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 9

The “Recharge Oscillator”:A simple paradigm for the ENSO cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

Neutral State

ShallowerMeanThermocline

Poleward Vg

anomaly L H V ~ dp/dx

Ocean Heat DischargeShallow thermocline >Cold SST via upwelling

Cold event

Positive feedback

Equatorward Vg

anomaly H L V ~ dp/dx

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 10

The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system)

F.-F. Jin, J. Atmos. Sci. 1997

Warm event

ThermoclineDepth anomaly

Wind stressanomaly

Positive feedback

Neutral State

ShallowerMeanThermocline

Poleward Vg

anomaly L H V ~ dp/dx

Ocean Heat DischargeShallow thermocline >Cold SST via upwelling

Cold event

Positive feedback

Equatorward Vg

anomaly H L V ~ dp/dx

Ocean Heat Recharge

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 11

The slab ocean El Niño

Based on the ECHAM5 atmosphere model in T31 (3.75° × 3.75°)

(a) the mean standard deviation for all slab simulations with the NINO3 SST stdv <0.8 K. (b) As Figure 1a, but for NINO3 SST stdv >0.8 K.

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 12

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The slab ocean El Niño Summing up

El Niño‐type of SST variability can exist entirely controlled by atmospheric feedbacks and ocean heat capacity.

While the results indicate that atmospheric processes only could potentially explain aspects of the ENSO mode that is not to say that ocean processes and dynamics are not important.

Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 17

ITF on ENSO dynamics CSIRO Mk3L model

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Mao-Lin Shen, Yu-Heng Tseng and Sen JanMao-Lin Shen, Yu-Heng Tseng and Sen JanPage 25112/04/21

Thank you for your attention.Questions?