2010 CMOS-CGU Congress
OCEAN
LAND
“   ...on average, ~70% of the temporal variability in
    drought frequency for the climate divisions [in the US]
    is ...
Precipitation has a power spectra that often resembles white noise



Mrs eNil - playing catch up!
IS PRECIPITATION EVER RED?
CRU TS2.1/GHCN
Using singular spectral analysis
   to decompose precipitation records




Ault and St. George, Journal of Climate, 2010
Decadal
Multidecadal      Interannual




Secular
                     Noise
Decadal
Multidecadal      Interannual




Secular
                     Noise
GEOGRAPHY MATTERS
Decadal ‘hotspots’ in winter precipitation




0%   10%              20%               30% variance
Ault and St. George, Journal of Climate, 2010
SPATIAL SMOOTHING


Ault and St. George, Journal of Climate, 2010
Decadal variability synchronizes rainfall, stream ow and hazards in northern California




Ault and St. George, Journal o...
characteristics of D2M ‘hotspots’

     !  Not correlated with major modes

     ! Do not track SST anomalies
     ! Are n...
D2M power is greatest in the ENSO-PDO ‘null’




                                                r (precipitation • PDO)
A...
TEMPORAL STABILITY
Tree-ring records
                from northern California
                and southern Oregon




St. George and Ault, un...
Tree rings indicate strong decadal behavior is restricted to 20th century




St. George and Ault, unpublished
GEOGRAPHY MATTERS
The strength of decadal and multidecadal behavior in
precipitation varies seasonally and across North Am...
PATTERNS DISTINCT FROM MAJOR MODES
Exceptionally strong decadal or multidecadal behavior in
terrestrial precipitation does...
STRONG ≠ FORCED?
Even for regions with exceptionally strong decadal
patterns, we cannot rule out the possibility that this...
2010 CMOS-CGU Congress
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The magnitude of decadal and multidecadal variability in North American precipitation

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The magnitude of decadal and multidecadal variability in North American precipitation

  1. 1. 2010 CMOS-CGU Congress
  2. 2. OCEAN
  3. 3. LAND
  4. 4. “ ...on average, ~70% of the temporal variability in drought frequency for the climate divisions [in the US] is explained by the PDO, AMO, and NH temperature. ” McCabe et al., PNAS, 2004
  5. 5. Precipitation has a power spectra that often resembles white noise Mrs eNil - playing catch up!
  6. 6. IS PRECIPITATION EVER RED?
  7. 7. CRU TS2.1/GHCN
  8. 8. Using singular spectral analysis to decompose precipitation records Ault and St. George, Journal of Climate, 2010
  9. 9. Decadal Multidecadal Interannual Secular Noise
  10. 10. Decadal Multidecadal Interannual Secular Noise
  11. 11. GEOGRAPHY MATTERS
  12. 12. Decadal ‘hotspots’ in winter precipitation 0% 10% 20% 30% variance
  13. 13. Ault and St. George, Journal of Climate, 2010
  14. 14. SPATIAL SMOOTHING Ault and St. George, Journal of Climate, 2010
  15. 15. Decadal variability synchronizes rainfall, stream ow and hazards in northern California Ault and St. George, Journal of Climate, 2010
  16. 16. characteristics of D2M ‘hotspots’ ! Not correlated with major modes ! Do not track SST anomalies ! Are not synchronized with each other
  17. 17. D2M power is greatest in the ENSO-PDO ‘null’ r (precipitation • PDO) Ault and St. George, Journal of Climate, 2010
  18. 18. TEMPORAL STABILITY
  19. 19. Tree-ring records from northern California and southern Oregon St. George and Ault, unpublished
  20. 20. Tree rings indicate strong decadal behavior is restricted to 20th century St. George and Ault, unpublished
  21. 21. GEOGRAPHY MATTERS The strength of decadal and multidecadal behavior in precipitation varies seasonally and across North America
  22. 22. PATTERNS DISTINCT FROM MAJOR MODES Exceptionally strong decadal or multidecadal behavior in terrestrial precipitation does not appear to be linearly related to the ‘usual suspects’ of major climate modes.
  23. 23. STRONG ≠ FORCED? Even for regions with exceptionally strong decadal patterns, we cannot rule out the possibility that this behavior is caused by processes with an underlying white spectrum.
  24. 24. 2010 CMOS-CGU Congress

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