Historical & Climatic Context for Multiseasonal,
Multiyear, & Multibasin Droughts
Julio Betancourt
Desert Laboratory
Coauthors
Greg McCabe, USGS, WRD, Denver
Mike Palecki, Illinois State Water Survey
Steve Gray & Lisa Graumlich, Greg Pederson,
Montana State University
Forest Health Monitoring Working Group
Sedona, Arizona
February 10, 2004
Utah
Water Year
Precipitation
Colorado
Southwest Average
1941
18931904
UT CO
AZ NM
1956
1895-2002
2002
Arizona
New Mexico
Drought Area Index
Percent of area <-3 PDSI from 1901-2000
19311938
19511956
30%
50%
Composite Standardized Precipitation Anomalies
Water Year 1931-1938 vs. 1896-2000 Long-Term Average
1951-56 Precipitation anomalies relative
to long-term normal 1950-95
January-April
May-June
July-August
January-August
Composite Standardized Precipitation Anomalies
1999-1903 vs. 1896-2000 Long-Term Average
1999-2003
NCEP-NCAR
Reanalysis
SST Anomalies
1968-1996
1951-1956
-1
-8 -6 -4 -2
0
2
4
6
8
1
Pacific Decadal Oscillation
Warm Phase
Cool Phase
Monthly Values for the PDO Index, 1900-2000
Schmidt & Webb (2001)
Atlantic Multidecadal Oscillation
1900 1910
1920 1940 1950 1960 1970 1980
1990 2000
•10-yr running mean of detrended SST anomalies averaged
over N Atlantic from 0-70ºN with an amplitude of 0.4ºC
•Warm phases 1860-1880, 1930-1960, 1995-present
Cold phases 1905-1925 and 1970-1990
•Probable cause is natural, internal variations in THC &
associated meridional heat transport
•Inverse relation with ppn in central & western U.S. &
modulates ENSO teleconnection.
Enfield, Mestas-Nuñez & Trimble (2001)
Standardized Departure
3
West-Central U.S. =
30ºN to 50ºN
110 ºW to 90º W
2
1
0
-1
-2
5-yr annual 700 mb heights for central U.S.
5-yr annual N. Atlantic SST’s
-3
1945
1955
1965
1975
1985
1995
2005
700 mb Geopotential Heights (m) Anomalies 1948-1960 vs. 1968-1996
H
700 mb Geopotential Heights (m) Anomalies 1998-2003 vs. 1968-1996
H
Correlation
Correlation
Correlation
Temperature
Correlation
Precipitation
PDO
AMO
Principal Components Analysis of Drought
Frequency in the Conterminous U.S.
• Decompose drought frequency into its primary modes
of spatial & temporal variability
• Drought conditions assumed if annual precipitation in
lowest quartile (25%) of 100-yr record
• Drought frequency for 20-yr moving periods calculated
•
•
•
for each of 344 climate divisions (results same for
10 and 30-yr moving periods)
20-yr moving drought frequencies subjected to rotated
PC analysis w/ varimax rotation to identify primary modes
No a priori consideration of climate forcing factors
Scores and loadings of the PC analysis compared with
20-yr moving averages of PDO, AMO & NH temp. trend
McCabe, Palecki & Betancourt (2004)
PC #1 (r2= 0.24)
20yr drought frequencies
20yr moving PDO vs.
20yr drought frequencies
McCabe, Palecki & Betancourt (2004)
PC #2 (r2= 0.28)
20yr drought frequencies
20yr moving AMO vs.
20yr drought frequencies
McCabe, Palecki & Betancourt (2004)
PC
#3 (r2=Component
0.22)
Principal
3
20yr drought
(17% offrequencies
inter
20yr moving NH temp vs.
Northern
Hemispheric Warming
20yr drought frequencies
parallels with Drought
Frequencies
Red -> less droughts
Blue -> more droughts
McCabe, Palecki & Betancourt (2004)
McCabe, Palecki & Betancourt (2004)
Composite Standardized Precipitation Anomalies
1951-56 vs. 1896-2000 Long-Term Average
How probable are multiseasonal, multiyear, &
multibasin droughts?
Yellowstone
Seasonality of
Precipitation
J F M A M J J A S O N D
Basin, Wyoming
J F M A M J J A S O N D
Yellowstone
Bighorn
Basin
Flaming Gorge
Steamboat Springs
Colorado
Plateau
SW
Rockies
J F M A M J J A S O N D
J F M A M J J A S O N D
SE
Rockies
Tucson
J F M A M J J A S O N D
Tree-Ring Sites
In Central &
Southern Rockies
Santa Fe
J F M A M J J A S O N D
What is the source of regionally coherent, multidecadal precipitation
oscillations in the central & southern Rockies & adjacent regions?
a. Climate Regions
b. Yellowstone
Bighorn
Basin
Yellowstone
Colorado
Plateau
SW
Rockies
SE
Rockies
2.0
2.0
1.5
1.0
0.5
1.5
1.0
0.5
2
4
8
16
32
64
128
256
512
2
4
8
16
32
64
128
256
512
1400
0
RWI
1600
0.016 0.06
1800
1400
0
0.24 0.98
2.0
2.0
2.0
1.5
1.0
0.5
1.5
1.0
0.5
1.5
1.0
0.5
2
4
8
16
32
64
128
256
512
2
4
8
16
32
64
128
256
512
2
4
8
16
32
64
128
256
512
1400
0
1600
0.003 0.04
1800
0.15 0.49
1400
0
1600
0.006 0.05
1600
0.077 0.28
1.1
1800
1.9
f. SW Rocky Mountains
e. SE Rocky Mountains
d. Colorado Plateau
Period (Years)
c. Bighorn Basin
1800
0.15 0.45
1400
0
1600
0.057 0.18
1800
0.39 0.80
Power (RWI)2
Gray, Betancourt, Fastie,& Jackson 2003
Yellowstone
2.0
Multidecadal Variability &
Evidence for Multi-basin,
Multi-seasonal wet & dry spells
Yellowstone
Bighorn
Basin
2.0
1.5
1.5
1.0
1.0
0.5
0.5
2.0
1.5
1.5
1.0
1.0
0.5
0.5
2.0
2.0
1.5
1.5
1.0
1.0
0.5
0.5
2.0
Colorado
Plateau
SW
Rockies
2.0
1.5
1.5
1.0
1.0
0.5
0.5
2.0
SE
Rockies
Gray, Betancourt, Fastie,
& Jackson 2003
2.0
Bighorn Basin
Colorado Plateau
SE Rocky Mountains
SW Rocky Mountains
2.0
1.5
1.5
1.0
1.0
0.5
0.5
1300 1400 1500 1600 1700 1800 1900
Tree-Ring Sites for AMO Reconstruction
SST anomaly
0.4
0.2
Instrumental
AMO
0
-0.2
-0.4
1850
1900
1950
2000
Gray, Graumlich,
Betancourt, & Pederson in prep
Tree-Ring Reconstruction of AMO: Calibration
0.5
AMO r = 0.917
Annual SSTA r = 0.778
0.4
0.3
Atlantic SSTA (C)
0.2
0.1
0
-0.1
Annual SST Anomoly
AMO
-0.2
Predicted SSTA
Predicted AMO
-0.3
-0.4
-0.5
1890
1900
1910
1920
1930
1940
1950
Year
1960
1970
1980
1990
2000
Gray, Graumlich, Betancourt & Pederson in progress
Tree-Ring Reconstruction of AMO
NorthNorth
Atlantic
SSTA
(°C)
Atlantic SSTA
(C)
WARMER
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
Late 16th
Century Megadrought
0.6
0.8
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
Gray, Graumlich, Betancourt & Pederson, in progress
Biondi, Gershunov & Cayan (2001)
16671680
1730s
17721786
1750s
Gray, Graumlich & Betancourt, in progress
19051893- 1924 1950s
1904
Relationship of 20-yr Smoothed AMO & PDO
with Reconstructed PDSI
AD 1660-2000
AMO vs. PDSI
AMO- Atlantic
Multidecadal
Index (Gray,
Graumlich &
Betancourt,
In prep)
20-yr PDO
smoothed
PDOO vs. PDSI
vs. PDSI
correlation
PDSI- Palmer Drought Severity
Index (Cook, Meko, Stahle,
& Cleavland 1999)
PDO- Pacific
Decadal
Oscillation
(Biondi,
Gershunov,
& Cayan 2001)
?
?
McCabe, Palecki & Betancourt (2003)
+PDO
-AMO
+PDO +AMO
25% = normal
-PDO
-AMO
.
-PDO
+AMO
McCabe, Palecki & Betancourt (2003)
.
Experimental Unofficial Two-class Monthly & Seasonal
Climate Outlooks February-March-April 2004
NOAA
CPC
Conclusions
• Spatiotemporal patterns in U.S. drought frequencies are
associated with AMO & PDO in both the instrumental &
tree-ring record of the last 500 years.
• AMO primarily influences summertime precipitation, but
it may also modulate the average latitude & sinuosity of
the westerlies (+AMO = H pressure over western states)
• Multiseasonal, large-scale droughts result from
complementary modes of the AMO (+) and PDO (-)
• Current ocean configuration foretells continuing drought
• Severe, multiyear and subcontinental droughts play key
roles in natural landscape responses to climate variability
and could accelerate the impacts of climate change
<< FHM Working Group Agenda
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