Eric Salath

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Constructing regional climate change scenarios
Eric Salathé Climate Impacts Group
(JISAO/SMA)University of Washington
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What do Global Models do?

• Simulate the global circulation patterns
• Can be derived from observations for verification
• Precipitation and Temperature is what would occur
  with global circulation and smooth Earth
• Does not correspond to observations

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Local Scaling
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Effect of Wind Patterns
Wind from South
Wind from Southwest
Strong Rainshadow
Weak Rainshadow
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Monthly Flow in Yakima River
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Downscaled ECHAM4 IPCC A2 -121.7 47.5 (Snoqualmie
Pass)
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Delta method -- scale the historic data by the
climate-change signal
Statistical downscaling,-- remove bias in
climate-change Precipitation using the historic
data
The choice is where the time-series
characteristics are taken from History or Model?
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What is the Climate Signal?
Percent of years with precipitation In bottom
20 of Historic Range
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Regional Climate Models

• Probably not best primary tool for impact studies
• Several research issues
• 1. Second Order effects
• Cold air outbreaks
• marine layer moves inland.
• 2. Orographic precipitation response to warming
• 3. ENSO response

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Comparison of RCM and Statistical Downscaling Of
Reanalysis GCM Arbitrary point on Cascade
Crest
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Regional Climate Models

• Probably not best primary tool for impact studies
• Several research issues
• 1. Second Order effects
• Cold air outbreaks
• marine layer moves inland.
• 2. Orographic precipitation response to warming
• 3. ENSO response

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Summary

• 1/8-degree P, Tmin, Tmax for IPCC scenarios
• What information should we take from models?
• What information should we take from historic
  record?
• What can we (should we) learn from regional
  climate models?