Coherence between the Great Salt Lake level and the Pacific quasi‐decadal q
oscillation
S.‐Y. (Simon) Wang1, R. R. Gillies12, J. Jin23, and L. E. Hipps2
1. Utah Climate Center, Utah State University.
1
Utah Climate Center Utah State University
2. Department of Plants, Soils, and Climate, Utah State University.
3. Department of Watershed Sciences, Utah State University.
Cyclic behavior of intermountain rainfall…
USU: Utah State University ( )
PDSI: Palmer Drought Severity Index
PDSI: Palmer Drought Severity Index year
Instrumental records are too short…
Is this 12
Is this 12‐‐yr, “quasi‐
yr, “quasi‐decadal cycle” for real?
Tree ring‐reconstructed precipitation record (Gray et al. 2003)
mm
Å 12‐yr cycle
Å Secular
total
776 years
Variance (mm2)
104
103
↑
PDO
↑
Secular
↑
QDO
Period (year)
256 128 64
32
16
8
4
The Great Salt Lake
P
Power
spectrum
t
• rain gauges
Closed‐basin lake in arid area
with no outlet
⎯ 6‐yr lowpass
6 l
lake volume change
water budget for
closed‐basin lake
Great Salt Lake Flood Æ
West Desert P
Pumping
mping Project
∆V = P + R0 − E − D
(Æ P leads lake volume by a quarter‐phase,
regardless of time scale; Lall and Mann 1995)
Where does the quasi‐decadal forcing come from?
GSL
SST
Strong QDO in Nino4
Strong QDO in Nino4
6‐yr lowpass
y
p
MTM (multitaper method)
spectral coherence
∆V = P + R0 − E − D
(i.e. P leads GSL volume by a quarter phase,
regardless of time scale; Lall and Mann 1995)
Each Pacific mode
exhibits a complete
evolution
SST SLP
SST, SLP
25‐40 yr
9‐13 yr
4‐5 yr
2‐3 yr
Extreme phase
T
Tourre
et al. (2001 GRL)
t l (2001 GRL)
A half cycle
Transition phase
Extreme phase
The Pacific Quasi‐Decadal Oscillation:
Q
SST and teleconnection patterns
ψQ: moisture flux streamfunction
sea surface temperature
Extreme phase
h
H
Transition phase
Transition phase
L
Regional impact:
Correlation map
Correlation map
L
L
Ï Extreme phase
well known
Gershunov and Barnett
(1998; BAMS)
(1998; BAMS) (PDO)
Ï Transition phase
Hydrological impact
on GSL:
Data: NCEP1 + stations
precipitation
moisture convergence
moisture storage
moisture storage
evaporation
∂W
+ ∇ ⋅ Q = E − P,
∂t
∆V = P + R0 − E − D
∂W
+ ∇ ⋅ Q = R0 − ∆ V
∂t
Eq.(1)
streamflow
GSL volume change balanced with
residual of Eq.(1)
Combined terrestrial & atmospheric
water budget analysis
drought severity
How can we use this linkage?
Warm-to-cool & cool-to-warm transitions
Warm
3 yr
°C
feet
ccm
Cool
6 yr
((=1/2 /
3 yr QDO)
Nino4 SST being
Nino4
SST being
a good predictor
for P and GSL!
But,…
• Need constant monitoring of SST & circulation patterns
• Take into account other climate modes (
T k i t
t th
li t
d (e.g. PDO / interannual
i t
l)
Extreme phases Æ 3 yrs later Æ transition phase
Pil t t di th t
Pilot studies that are done:
d
2009 GRL – Quadrature phase coupling of Intermountain rainfall with Pacific QDO
2009 JCLI – Hydrological impact of Pacific QDO on Great Salt Lake watershed
2009 CliDy – Dynamics of the Pacific QDO teleconnection
Applications and future studies:
• Evaluate GCMs or CFS on the QDO teleconnection
• Climate prediction for Utah: up to 3 yrs for P and 6 yrs for GSL level
• Dynamic downscaling for future scenarios
MTM coherence (length) and phase (direction)
UDel precip vs. SST (1900‐2008; 10‐15 yr frequency band)
vs SST (1900 2008; 10 15 yr frequency band)