Geoscience Reference
In-Depth Information
(a)
PDO
IPO
LF SST EOF 3, explains 2.9% of total variance
90 N
60 N
5
-15
30 N
-5
0
5
0
-5
-10
0
-15
10
-10
5
0
0
30 S
-10
0
-5
60 S
90 120 E
180
120 W60 W
0
60 E
120 E
(b)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
80
°
N
80
°
N
40
°
N
40
°
N
0
°
0
°
40
°
S
40
°
S
80
°
S
80
°
S
100
°
W
E
LONGITUDE
0
°
100
°
E
100
°
W
E
LONGITUDE
0
°
100
°
E
POSITIVE IPO AND EL NIÑO
NEGATIVE IPO AND EL NIÑO
Figure 2.10 (a) Spatial pattern of near-global SSTs indicative of the PDO and IPO phenomena. The PDO diagram is from
http://www.iphc.washington.edu/Staff/hare/html/decadal/decadal.html and the IPO panel is the second EOF pattern from
the analysis of Folland et al.( 1999 ). (b) Probability of exceeding median October-December rainfall over the globe during El
Ni˜o events with positive (left panel) and negative (right panel) IPOphase in the previous September. (Derived from the work of
Meinke et al. 2001 ) For color version see Plate 4 .
modes occur in the climate system. The major question about such modes is
whether they arise from stochastic processes or are the result of distinct
physical mechanisms. Recently White and Tourre ( 2003 ) have postulated
that distinct physical processes indicative of the operation of the delayed
oscillator mechanism that drives LF ENSO fluctuations, also power higher
frequency QB and lower frequency quasi-decadal variability across the
Pacific domain. These processes were found to generate progressively slower
westward-propagating off-equatorial Rossby waves at increasingly higher
latitudes for QB, LF ENSO, and quasi-decadal modes. These waves, along
with eastward-propagating equatorial coupled waves generated by the above
processes, were found to be primarily responsible for the overall periodicity
 
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