ENSO and ITF
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Transcript of ENSO and ITF
ENSO and ITF
Mao-Lin Shen
October 26, 2010
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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).
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Oceanic Thermocline
Tropical Atmosphere Ocean (TAO) Buoy Array (since ~1983)
0 m
200 m
400 m
Dep
th
T (z)Oct 2007
wind
thermocline
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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
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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.
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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.
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ITF on ENSO dynamics CSIRO Mk3L model
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Thank you for your attention.Questions?