A tree-ring based reconstruction
of North Pacific Jet variability
and its influence on Sierra
Nevada fire regimes
Valerie Trouet, Flurin Babst, David Stahle, Alan
Taylor, Carl Skinner, Julio Betancourt
20th C California fire weather
R=0.41; p<0.05
Trouet et al. (2008) TAC
Francis and Vavrus (2012) GRL
Correlation between
latitudinal winter
NPJ position
and April 1 SWE
Valérie
Trouet
18.06.2010
Valérie
Trouet
18.06.2010
The „liberal“
polar vortex
Correlation between
latitudinal winter
NPJ position
and April 1 SWE
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Correlation between
latitudinal winter
NPJ position
and April 1 SWE
70
80
correlation against NPJ
−160
−140
−120
−100
−80
−60
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20
Correlation between
latitudinal winter
NPJ position
and April 1 SWE
70
80
correlation against NPJ
−160
−140
−120
−100
−80
−60
Meko et al. (2011) Quat Int; Stahle et al. (2013) Earth Int
Blue Oak chronology vs.
DJF precipitation
CA vs. NR (1935-1999)
r=-0.42, p<0.001
1.8
-0.6
1.6
-0.8
1.4
-1
1.2
1
-1.2
0.8
-1.4
CA
0.6
NR
0.4
-1.6
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
55
1935-1989: 40.4 N
latitudinal NPJ position N
50
45
40
35
30
25
1935
1945
1955
1965
1975
year
1985
1995
2005
2015
1990-2013: 37.9 N
instrumental vs. reconstructed NPJ
r=0.55, p<0.001
55
latitudinal NPJ position N
50
45
40
35
30
NPJ target
NPJ reconstructed
25
1935
1945
1955
1965
year
1975
1985
1995
Running correlation CA vs. NR (1650-1999)
0.4
0.2
r-value
0
-0.2
-0.4
-0.6
1650
1700
1750
1800
1850
1900
1950
Valérie
Trouet
18.06.2010
Wise and Dannenberg 2014 Nature Comms
Row 1
20
10
25−year running sum
0
1550
1650
1750
1850
1950
Row 2
20
10
0
1550
1650
1750
1850
1950
1850
1950
Row 3
20
10
0
1550
1650
1750
Figure 5 | Persistence of GPH anomaly patterns over time in SOM rows.
standardized and calibra
estimate the withheld va
decades in the series. To
of data preceding and f
model. Following mode
standardized over the ca
reconstruction model an
stepwise approach12,13 i
the imputed values were
was applied to successiv
Synoptic climatologica
http://www.cis.hut.fi/som
quency and persistence o
time. SOM is a neural n
than discrete classes and
use of an iterative cluste
make an a priori decisio
false discovery rate tech
which one or more pair
indistinguishable at the
25), local two-sample tto every possible pair of
probability of ‘false disc
false discovery rate test
values resulting from ea
Row 1
20
10
25−year running sum
0
1550
1650
0.6
1750
1850
1950
Row 2
0.4
20
Synoptic climatologica
CA
vs NR
http://www.cis.hut.fi/som
0.2
10
0
01550 1600
1550
-0.2
1650
1700
1650
1750
1800
1750
1850
1850
1900
1950
1950
-0.4
Row 3
20
10
0
standardized and calibra
estimate the withheld va
decades in the series. To
of data preceding and f
model. Following mode
standardized over the ca
reconstruction model an
stepwise approach12,13 i
the imputed values were
was applied to successiv
1550
1650
1750
1850
1950
Figure 5 | Persistence of GPH anomaly patterns over time in SOM rows.
quency and persistence o
time. SOM is a neural n
than discrete classes and
use of an iterative cluste
make an a priori decisio
false discovery rate tech
which one or more pair
indistinguishable at the
25), local two-sample tto every possible pair of
probability of ‘false disc
false discovery rate test
values resulting from ea
Westerling et al. (2006) Science
•  350 sites
•  3000 trees
•  27000 fire scars
•  Pinus ponderosa
Taylor et al. (2007)
33 Fire Scars
1889 LW
1879 ME
1854 LE
1840 D
1828 D
1821 LE
1809 D
1799 D 1793 D
1787 LW
1781 ME
1775 D
1771 D
1765 LW
1200000
annual area burned (ha)
1000000
800000
600000
400000
200000
0
1600
1650
1700
1750
1800
1850
1900
1950
2000
Conclusions Tree-­‐ring data can be used to reconstruct decadal-­‐scale NPJ variability back to ~1870. CA-­‐NR dipole breaks down prior to 1870 possibly due to shiD from zonal (1850-­‐1900) to meridional (1900-­‐present) flow. Through its influence on snowpack, winter NPJ variability impacts fire acOvity in the Sierra Nevada. Sierra Nevada fire regimes and fire-­‐climate interacOons have been modulated by land-­‐use changes since the 18th Century.