Oscillations and teleconnections - The Global Climate System: Patterns, Processes, and Teleconnections - page 40

Figure 2.5 Monthly
Southern Oscillation Index
(SOI) values from January
1866 until September 2002,
smoothed with an 11-point
running average (except for
end points). ''El Ni˜o-like''
conditions are negative and
''La Ni˜a-like'' conditions are
positive.

25
15
5
-5
-15
-25
25
15
5
-5
-15
-25
25
15
5
-5
-15
-25

1860 1870 1880 1890 1900 1910

1910 1920 1930 1940 1950 1960

1960 1970 1980 1990 2000 2010

Figure 2.6 Multi-taper
frequency-domain singular
value decomposition (MTM-
SVD) localised variance
spectrum (LFV) from a joint
analysis of HadCRUTv (OI)
and HadSLP (OI) from 1871
to 1998 (relative variance is
explained by the first
eigenvalue of the SVD as a
function of frequency) over
the domain 65 8 N-35 8 S.
The 50, 90 and 99%
statistical confidence limits
are shown as horizontal
lines, and various significant
climatic features in the
spectrum are pointed out on
the diagram.

PERIOD (YEARS)

16 8 4 2

0.9

ENSO 2.5-8 yr

QB 2-2.5 yr

0.8

64 yr

11.5 yr

0.7

16.8 yr

99%

0.6

95%

90%

0.5

50%

0.4

0 0.0625 0.125 0.1875 0.25 0.3125 0.375 0.4375

FREQUENCY (CYCLES/YEAR)