Observed precipitation impacts of SAM

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Observed precipitation impacts of SAM
Visbeck
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(No Transcript)
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Hendon,Thompson,Wheeler 2006)
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(No Transcript)
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Using CPC SAM index
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SLP station data based index for the Southern
Annular Mode

• Average all data in two zonal bands and compute a
  first guess SAM index.
• Correlate all stations with the first guess
  index.
• Divide the subtropics into three regions and
  generate averaged pressure anomaly index for each
  region.
• Compute pressure anomaly index for Antarctic
  stations.

Courtesy Martin Visbeck
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SLP station data based index for the Southern
Annular Mode
Construct final SAM index from the normalized sum
of the three subtropical high indices and the
(negative) Antarctic low index. However index
starts only 1950
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Courtesy Bertrand Timbal and Martin Visbeck
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Courtesy Julie Arblaster
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• Strong seasonality of terrestrial response to SAM
• Attributing recent climate variability to trends
  of the SAM requires reliable index of the SAM,
  especially changes in seasonal variability
• (careful intercomparison of SAM indices?)
• Future climate change depends on seasonality of
  changes in the SAM are the mechanisms of low
  frequency changes in the SAM understood/robust?
  What role does the SO play and are the mechanisms
  of two way interaction faithfully represented in
  climate models?

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DJF
JJA