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Tropical Pacific decadal oscillation driven by the interaction between ENSO and mean state

Tropical Pacific decadal oscillation driven by the interaction between ENSO and mean state. Jung Choi , Soon-Il An Climate Theory Laboratory, Department of Atmospheric Sciences, Yonsei University, Seoul, Korea. Introduction. Fedorov & Philander(2000).

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Tropical Pacific decadal oscillation driven by the interaction between ENSO and mean state

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  1. Tropical Pacific decadal oscillation driven by the interaction between ENSO and mean state Jung Choi , Soon-Il An Climate Theory Laboratory, Department of Atmospheric Sciences, Yonsei University, Seoul, Korea

  2. Introduction Fedorov & Philander(2000) • ENSO-like interdecadal variability in Tropical Pacific (Tropical Pacific Decadal Variability) ~ Decadal ENSO amplitude modulations • The physical mechanism is still unknown.

  3. Introduction TPDV ENSO External influence TPDV SeasonalCycle Internal mode ENSO

  4. Data (Dewitte et al. (2006, 2007), Cibot et al. (2005))

  5. ENSO modulation

  6. Wavelet of Nino3 SSTA Averaged power (2-7yr waves)  N3Var index (Torrence & Webster) Biennial ENSO

  7. N3Var index • ENSO modulation (16-year)

  8. Correlation between ENSO and mean state

  9. Changes of mean state • Lowpass-filtered (>7yr) SSTA , D17 (LSST) (LD17)

  10. Correlations N3Var LD17 LSST High-Var regime Correlation :: (N3Var ~ LD17)0.54 Low-Var regime

  11. Nonlinear rectification(ENSO mean state)

  12. Asymmetry of ENSO • EOF of Highpass-filtered (<7yr) D17 Mature phase Transition PC Transition phase Mature phase PC

  13. Positive feedback? Residual heat content rectifies the mean state. ENSO Decadal variability Mean state supports the High-Var ENSO conditions.

  14. Role of mean state(mean state ENSO)

  15. Eigen analysis Background field (mean state) SST, Wind, Thermocline depth, Upwelling ... etc. Based on CZ intermediate ENSO model Generate Matrix Eigenanalysis 1st Eigenvector(most unstable mode)

  16. Experimental design High-Var regime 1 1 2 4 2 3 3 Low-Var regime 0.5 0.5 Normalized PC1 of LD17 - - 0.5 0.5  Composite the mean state on each 1,2,3,4 (SST, thermocline depth)

  17. ENSO Growth rate & Frequency SST+TH 1 SST 1 1 TH

  18. Damp down ENSO ENSO unstable regime Increasing of Growth rate Cooling SST in E. Pacific Shoaling H in E. Pacific Increasing asymmetry & amplitude of ENSO Warming SST in E. Pacific Deepening H in E. Pacific Decreasing asymmetry & amplitude of ENSO Sustain ENSO Reduction of Growth rate ENSO stable regime < Schematic diagram for TPDO >

  19. Thank You !

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