1. ENSO and ITF Mao-Lin Shen October 26, 2010

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).

3. Oceanic Thermocline Tropical Atmosphere Ocean (TAO) Buoy Array (since ~1983) wind 0 m 200 m 400 m T (z) Oct 2007 Depth thermocline

4. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Warm event Wind stress anomaly Thermocline Depth anomaly Positive feedback F.-F. Jin, J. Atmos. Sci. 1997

5. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Warm event “Bjerknes Feedback” positive SST anomaly negative SLP anomaly westerly wind anomaly deepened thermocline positive SST anomaly Wind stress anomaly Thermocline Depth anomaly Positive feedback F.-F. Jin, J. Atmos. Sci. 1997

6. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Warm event Wind stress anomaly Thermocline Depth anomaly Poleward Vg anomaly L H V ~ dp/dx Positive feedback F.-F. Jin, J. Atmos. Sci. 1997

7. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Neutral State Warm event Wind stress anomaly Shallower Mean Thermocline Thermocline Depth anomaly Poleward Vg anomaly L H V ~ dp/dx Positive feedback Ocean Heat Discharge F.-F. Jin, J. Atmos. Sci. 1997

8. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Neutral State Warm event Wind stress anomaly Shallower Mean Thermocline Thermocline Depth anomaly Poleward Vg anomaly L H V ~ dp/dx Positive feedback Shallow thermocline > Cold SST via upwelling Ocean Heat Discharge Positive feedback F.-F. Jin, J. Atmos. Sci. 1997 Cold event

9. The “Recharge Oscillator”:A simple paradigm for the ENSO cycle(Instability of the tropical Pacific ocean-atmosphere system) Neutral State Warm event Wind stress anomaly Shallower Mean Thermocline Thermocline Depth anomaly Poleward Vg anomaly L H V ~ dp/dx Positive feedback Shallow thermocline > Cold SST via upwelling Ocean Heat Discharge Equatorward Vg anomaly H L V ~ dp/dx Positive feedback F.-F. Jin, J. Atmos. Sci. 1997 Cold event

10. The “Recharge Oscillator”:A simple paradigm for the El Niño cycle(Instability of the tropical Pacific ocean-atmosphere system) Neutral State Warm event Wind stress anomaly Shallower Mean Thermocline Thermocline Depth anomaly Poleward Vg anomaly L H V ~ dp/dx Positive feedback Shallow thermocline > Cold SST via upwelling Ocean Heat Discharge Equatorward Vg anomaly H L V ~ dp/dx Positive feedback F.-F. Jin, J. Atmos. Sci. 1997 Cold event Ocean Heat Recharge

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.

16. 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.

17. ITF on ENSO dynamics CSIRO Mk3L model

25. Thank you for your attention. • Questions?