North Atlantic Oscillation: the nonlinear aspect and its longrange prediction

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North Atlantic Oscillationthe non-linear aspect
andits long-range prediction

• Wilbur Y. Chen
• Climate Prediction Center
• NCEP/NWS/NOAA

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Precursors? Where? Non-linear nature of
precursors NAVs Circulation Regime matching
approach (a framework for long-range
prediction?) Varying predictability within
NAV (while invariant for NAO) Prediction
skill scores
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NAO Index
Correlation with NAO Index
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NAO Index lags
NAO Index leads

• Season
• Seasons
• Seasons
• 4 Seasons

• Season
• Seasons
• Seasons
• Seasons

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5
One-year lead precursor
results in NAO
SON -gt DJF
JJA -gt DJF
MAM -gt DJF
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Composites 1-yr later
Most likely clusters
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4
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DJF 91 ? DJF 92
Verification for DJF 92
Given DJF 91
AC 0.83
leads
Cluster of Analogues in DJFs
Forecast for DJF 92
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