AAO

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AAO
Units 106 m2/s
AO
PNA
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Lau, 1988
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The problem SELF-feedback
how to relate anomalous eddy- induced forcing
to anomalous low-frequency flow itself
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Why should we care? A key element for a) Why
there are NAO, AAO, PNA in the stormy
atmospheric circulation? b) Low-frequency
dynamics in general c) Extra-tropical
ocean-atmosphere interaction, etc.
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A new and constructive approach A barotropic
framework as an example
Basic state
For low-frequency flow
Analytical SELF feedback operator
Extensions to QG baroclinic or PE
models are straight forward.
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Validation of the approach
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Observed AAO related
By only using AAO pattern
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Observed AO related
By only using AO pattern
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Observed PNA related
By only using PNA pattern
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A unified theory for AAO, AO
AAO and AO are the least damped internal modes
in the linear dynamic system with SELF-feedback
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Leading SVD mode
Observed AO
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Leading SVD mode
Observed AAO
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Surface pressure
Zonal flow
SDV
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• Summary
• A new approach is proposed to delineate the
  synoptic eddy and low-frequency flow (SELF)
  feedback.
• A linear dynamic operator for SELF-feedback is
  derived and validated.
• AAO, AO can be understood as the least damped
  internal modes of linear dynamic system with
  SELF-feedback.

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Lau, 1988
Pacific and Atlantic Storm tracks
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Variances of C-EOF modes
Auto-correlation
days
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positive SELF feedbacks Conceptual model