Trend and Variability of East-Asian Precipitation: Linkage to Sea Surface Temperatures

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Trend and Variability of East-Asian
Precipitation Linkage to Sea Surface
Temperatures

• Fanglin Yang
• Environmental Modeling Center
• National Centers for Environmental Prediction
• NOAA 32nd Climate Diagnostic and Prediction
  Workshop
• COAPS/FSU, October 22-27, 2007
• Acknowledgment This work was support by the
  NASA Modeling, Analysis and Prediction program
  while the author worked with William Lau at
  GFSC/NASA.

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• Possible causes
• South Asian black carbon emission
• Climate regime shift
• Global warming
• Shift of Africa-North China teleconncection
• SST trend

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North China
Central China
South China
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MAM
JJA
Interannual lt 7 years
Inter-Decadal gt7 years
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Questions?

• To what extent can the observed precipitation
  variability can be explained by SST variability?
• Does the precip-SST relation at the interannual
  timescale differ from that at the inter-decadal
  timescale?

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Interannual Variability

• Single Value Decomposition (SVD) applied to
  7-year high-pass filtered precipitation and SSTs

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MAM
SST
Precip
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JJA
SST
Precip
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JJA, Regressions of wind850 and Z700 to PCs
SVD Modes
JJA Climate, 1951-1998, NCEP R1
SST_PC
Precip_PC
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MAM
SST_PC
Precip_PC
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• Decadal Variation and Trend

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SST Interannual Mode
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Rainfall Interannual Mode
Projection of Obs to SVD mode
Area-Mean Rainfall
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Conclusion

• Interannual Variability
• Precipitation over South China in MAM and North
  China in JJA ? ENSO mode of SSTs
• Precipitation over central China in both MAM and
  JJA season ? SST in warm pool and northern Indian
  ocean
• Features of the anomalous 850-hPa winds and
  700-hPa geopotential height corresponding to
  these modes support a physical mechanism that
  explains the causal links between the modal
  variations of precipitation and SSTs.

• Trend and decadal variation
• Upward South China MAM precipitation and
  downward JJA North China precipitation ? warming
  trend of the ENSO-like mode.
• Upward JJA central China precipitation ?
  warming trend of SSTs over the warm pool and
  Indian Ocean.
• Downward MAM South China precipitation ?
  downward central North Pacific SSTs (less robust)

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