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Initialization Strategies for the CFS

Initialization Strategies for the CFS. Ben Kirtman, Eric Altshuler, Kathy Pegion George Mason University and the Center for Ocean-Land-Atmosphere Studies. The Initial Condition Problem. Best State Estimate Data Assimilation in the Separate Component Models

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Initialization Strategies for the CFS

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  1. Initialization Strategies for the CFS Ben Kirtman, Eric Altshuler, Kathy Pegion George Mason University and the Center for Ocean-Land-Atmosphere Studies

  2. The Initial Condition Problem • Best State Estimate • Data Assimilation in the Separate Component Models • Maybe Not Ready to Do the Coupled Assimilation Problem • Coupled Model Climate ≠ Observed Climate • Anomaly Initialization • Coupled “Modes” of Coupled Model ≠ Observed Coupled “Modes” • Initializing the Coupled Modes • Identifying the Coupled Modes: EOFs, SVDs, … • Context of the Forecast Environment

  3. GODAS CFS Simulation Drift

  4. GODAS CFS Simulation Drift

  5. Coupled Ocean-Atmosphere Initialization CFS Forecast CFS Simulation Observations SSTA Standard Deviation as Function of Month

  6. The Initial Condition Problem • Best State Estimate • Data Assimilation in the Separate Component Models • Maybe Not Ready to Do the Coupled Assimilation Problem • Coupled Model Climate ≠ Observed Climate • Anomaly Initialization • Coupled “Modes” of Coupled Model ≠ Observed Coupled “Modes” • Initializing the Coupled Modes • Identifying the Coupled Modes: EOFs, SVDs, … • Context of the Forecast Environment

  7. JAN 1997 JAN 1988 Anomaly Initialization CFS Control GODAS

  8. Why Did the Forecasts Bust? • Predictability Issue • Not Enough Ensemble Members • What Actually Happened was an Outlier • Westerly Wind Burst • Something Wrong with Initial Conditions • Anomaly Initialization Did Not Help • Coupled Modes of the Coupled Model

  9. CFS Forecast Ensemble Mean GODAS

  10. ENSO Precurser Three Month Lead CFS Forecasts GODAS CFS Simulation

  11. ENSO Precurser Nine Month Lead CFS Forecasts GODAS CFS Simulation

  12. The Initial Condition Problem • Best State Estimate • Data Assimilation in the Separate Component Models • Maybe Not Ready to Do the Coupled Assimilation Problem • Coupled Model Climate ≠ Observed Climate • Anomaly Initialization • Coupled “Modes” of Coupled Model ≠ Observed Coupled “Modes” • Initializing the Coupled Modes • Identifying the Coupled Modes: EOFs, SVDs, … • Context of the Forecast Environment

  13. Identifying the Coupled Modes • Forecast Environment • Analogue Approach • Heat Content/D20C Analogues Don’t Work Coupled Modes of Coupled Model are Not the Same as the Observations • Use Long Simulation to Identify “Best Fit” SST Evolution (9 Months) Relate Analogue “Initial State” to Observed Initial State

  14. “Initial Condition” D20C Analogues Do Not Work SSTA GODAS SSTA Forecast SSTA: Best D20C Analogue

  15. “Initial Condition” D20C Analogues Do Not Work D20C GODAS D20C Forecast D20C: Best D20C Analogue

  16. Forecast Evolution Analogues Do Work GODAS SSTA SSTA: Best SST Evolution Analogue

  17. Forecast Evolution Analogues Do Work GODAS SSTA SSTA: Best SSTA Evolution Analogue

  18. Forecast Evolution Analogues Do Work GODAS D20C D20C: Best SSTA Evolution Analogue

  19. Forecast Evolution Analogues Do Work GODAS D20C D20C: Best SSTA Evolution Analogue

  20. Initializing with the Coupled Modes • Use Long Simulation to Identify “Best Fit” SST Evolution (9 Months) • Relate Analogue “Initial State” to Observed Initial State • Singular Value Decomposition • Project, Reconstruct, Re-Forecast (Anomaly Initialization)

  21. Equatorial Pacific SSTA Forecast Initialized Coupled Modes CFS Control GODAS

  22. Nino34 SSTA Evolution CFS Control Initialized Coupled Modes GODAS

  23. Equatorial Pacific D20C Forecast Initialized Coupled Modes CFS Control GODAS

  24. Equatorial Pacific SSTA Forecast Initialized Coupled Modes CFS Control GODAS

  25. Nino34 SSTA Evolution Initialized Coupled Modes CFS Control GODAS

  26. Equatorial Pacific D20C Forecast Initialized Coupled Modes CFS Control GODAS

  27. Conclusions • Anomaly Initialization Not Much Help • Coupled Modes in Observations are not the Same as the Coupled Modes in the Model • ENSO Precurser, D20C Analogues Don’t Work • SSTA Evolution Analogues Show Promise • Need More Longer Simulations (Easy) • Need Many More Forecast Tests (Difficult) • Predictability Issues • WWB, Ensemble Size • Expand the Approach to the Coupled System • Blending or Nudging

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