1. 2010 CMOS-CGU Congress

2. OCEAN

3. LAND

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. Precipitation has a power spectra that often resembles white noise
Mrs eNil - playing catch up!

6. IS PRECIPITATION EVER RED?

7. CRU TS2.1/GHCN

8. Using singular spectral analysis
to decompose precipitation records
Ault and St. George, Journal of Climate, 2010

9. Decadal
Multidecadal Interannual
Secular
Noise

10. Decadal
Multidecadal Interannual
Secular
Noise

11. GEOGRAPHY MATTERS

12. Decadal ‘hotspots’ in winter precipitation
0% 10% 20% 30% variance

13. Ault and St. George, Journal of Climate, 2010

14. SPATIAL SMOOTHING
Ault and St. George, Journal of Climate, 2010

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

16. characteristics of D2M ‘hotspots’
! Not correlated with major modes
! Do not track SST anomalies
! Are not synchronized with each other

17. D2M power is greatest in the ENSO-PDO ‘null’
r (precipitation • PDO)
Ault and St. George, Journal of Climate, 2010

18. TEMPORAL STABILITY

19. Tree-ring records
from northern California
and southern Oregon
St. George and Ault, unpublished

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St. George and Ault, unpublished

21. GEOGRAPHY MATTERS
The strength of decadal and multidecadal behavior in
precipitation varies seasonally and across North America

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. 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. 2010 CMOS-CGU Congress