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C. Stan, D. Min, K. Pegion

C. Stan, D. Min, K. Pegion. ENSO Prediction and Predictability. Two Views of ENSO Predictability Linear Damped Stochastically Forced Non-Linear Chaotic System Practical Predictability CGCM Estimates of Prediction Skill Probabilistic vs. Deterministic

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C. Stan, D. Min, K. Pegion

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  1. C. Stan, D. Min, K. Pegion

  2. ENSO Prediction and Predictability • Two Views of ENSO Predictability • Linear Damped Stochastically Forced • Non-Linear Chaotic System • Practical Predictability • CGCM Estimates of Prediction Skill • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • CGCM Forecast Predictability • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • Multi-Model Approach • Testing IPCC Models • Model Errors

  3. Understanding Forecast Skill • What is the Overall Limit of Predictability? • What Limits Predictability? • Uncertainty in Initial Conditions: Chaos within Non-Linear Dynamics of the Coupled System • Uncertainty as the System Evolves: External Stochastic Effects • Model Dependence? • Model Error

  4. Damped Linear Dynamics Non-Linearity → Noise Noise Amplitude Unrelated to Signal Non-Normality and Spatial Structure of Noise Limit of Predictability (~12 Months) Variations in Predictability and ENSO Amplitude Modulation Random Unstable Fundamental Non-Linearity Non-Linear Control of Growth Details of Noise Relatively Unimportant Signal and Noise Amplitude Dependence Limit of Predictability (~18 Months) Variations in Predictability and ENSO Amplitude Modulation Fundamental ENSO: Damped or Unstable?

  5. ENSO Prediction and Predictability • Two Views of ENSO Predictability • Linear Damped Stochastically Forced • Non-Linear Chaotic System • Practical Predictability • CGCM Estimates of Prediction Skill • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • CGCM Forecast Predictability • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • Multi-Model Approach • Testing IPCC Models • Model Errors

  6. 15-member CFS reforecasts 15-member CFS reforecasts

  7. Are We Fooling Ourselves? • Empirical Prediction • Rigorous Cross Validation (Exposed Artificial Skill) • Yet, in Real Prediction Skill Much Lower • Dynamic Prediction • Hidden Artificial Skill • Model Tuning • No Substitute for Real Prediction

  8. Understanding Forecast Skill • What is the Overall Limit of Predictability? • What Limits Predictability? • Uncertainty in Initial Conditions: Chaos within Non-Linear Dynamics of the Coupled System • Uncertainty as the System Evolves: External Stochastic Effects • Model Dependence? • Model Error

  9. ENSO Prediction and Predictability • Two Views of ENSO Predictability • Linear Damped Stochastically Forced • Non-Linear Chaotic System • Practical Predictability • CGCM Estimates of Prediction Skill • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • CGCM Forecast Predictability • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • Multi-Model Approach • Testing IPCC Models • Model Errors

  10. Effect of Increasing Ensemble Size From DEMETER (ECMWF)

  11. ENSO Prediction and Predictability • Two Views of ENSO Predictability • Linear Damped Stochastically Forced • Non-Linear Chaotic System • Practical Predictability • CGCM Estimates of Prediction Skill • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • CGCM Forecast Predictability • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • Multi-Model Approach • Testing IPCC Models • Model Errors

  12. CCSM3.0 Jan 1982 IC CFS Jan 1982 IC

  13. CCSM3.0 Jan 1983 IC CFS Jan 1983 IC

  14. CCSM3.0 Jan 1986 IC CFS Jan 1986 IC

  15. CCSM3.0 Jan 1988 IC CFS Jan 1988 IC

  16. CCSM3.0 Jan 1997 IC CFS Jan 1997 IC

  17. CCSM3.0 Jan 2006 IC COLA Jan 2006 IC

  18. Infamous Double ITCZ Problem

  19. Importance of Coupled Feedbacks

  20. ENSO Prediction and Predictability • Two Views of ENSO Predictability • Linear Damped Stochastically Forced • Non-Linear Chaotic System • Practical Predictability • CGCM Estimates of Prediction Skill • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • CGCM Forecast Predictability • Probabilistic vs. Deterministic • Noise: Initial Condition vs. Forecast Evolution • Multi-Model Approach • Testing IPCC Models • Model Errors

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