US Precipitation and Temperature Trends

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US Precipitation and Temperature Trends

• Dr. Imke Durre

Contact Imke.Durre_at_noaa.gov 1 828
271 4870
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Annual US-Averaged Precipitation
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M
Model precipitation projections, smoothed with a
13-year filter.
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Precipitation What happened and why?

• Seasonal differences in spatial patterns of
  trends in amount
• Precise seasonal evolution of trends?
• Relevant factors?
• Increased frequency of heavy events during the
  past three decades
• Sensitivity to analysis technique?
• Interdecadal variability or global warming?
• Frequency distribution of amounts
• Are we observing it correctly?
• Do we understand its variations?

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Annual US-Averaged TMAX/TMIN
1979-2005 TMAX Trend 0.30 C/Decade TMIN Trend
0.31 C/Decade
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Annual US-Averaged DTR
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from Dai et al. (2006)
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Surface Air Temperature trends 1958-1999 (DJFM)
from Quadrelli and Wallace (2004)
Component of trend thats linearly congruent with
the two leading PCs of the detrended SLP field.
Residual Trend
Linear Trend
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Temperature What happened and why?

• Trend towards fewer cold days in winter
• Boundary layer feedbacks?
• Summertime diurnal asymmetry in trends
• Water vapor feedback?
• Significant local trends
• Natural?

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Winter Inversions Heights of Warmest Levels
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Tucson
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Negative Correlations Between 850-SFC
Precipitable Water and Cooling Rate
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Major Challenges

• What's natural and what isn't?
• Significant local temperature trends
• Precipitation characteristics and changes
• Addressing shortcomings of linear trends
• Need for less arbitrary methods for analyzing
  variations
• Need for diagnosing simultaneous observed
  variations in
• multiple variables
• Local versus large-scale feedbacks
• Relative importance?
• Interactions?
• Role of the boundary layer?