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9-13 years is most prominent with another multidecadal peak centered at
around 15-20 years. The latter, probably indicative of the PDO/IPO phenom-
enon, is detailed in the next section. The use of an evolutive LFV spectral
option in the MTM-SVD technique permits an analysis of significant climatic
phenomena from one epoch to the next. This approach highlights the distinct
waxing and waning of QB, LF and quasi-decadal signals in the climate
system over the historical record (Allan
2000
; White and Tourre
2003
).
Interestingly, this tendency is manifest across all of the climatic signals
examined, and embraces a range of permutations in which robust and weak
phases in these signals can be coherent or incoherent at any time. Similar
results can be achieved using wavelet analysis methods (Torrence and
Webster
1999
).
The MTM-SVD signal detection method can also be employed to generate
canonical patterns that reveal the spatial structure and temporal evolution of
each dominant signal resolved by the LFV spectrum in Figure
2.6
. This can be
done for any one data field or in a joint mode using two data fields.
Experiments using combinations of surface temperature, MSLP, and preci-
pitation data in the joint MTM-SVD mode have shown that they resolve very
similar LFV spectral peaks, and thus joint canonical patterns can be derived
for each peak. As the precipitation set used in this study is a monthly global
land and island rainfall data set, derived originally from Hulme (
1992
) and
updated (1900-1998) on the Climatic Research Unit (CRU), University
of East Anglia's website (www.cru.uea.ac.uk/
mikeh/datasets/global/), our
joint MTM-SVD canonical analysis results are derived from the 1900 to 1998
period. The initial focus here is on the QB, LF and quasi-decadal signals,
followed by an examination of the ''ENSO-like'' PDO/IPO and its apparent
modulation of LF ENSO events (see Bove and O'Brien
2000
).
Canonical patterns of surface temperature, MSLP, and precipitation are
constructed at QB, LF and quasi-decadal time scales from the joint MTM-
SVD analysis, and are shown at 0, 45 and 90 degrees of phase in their
can complete the sequence to a full half cycle visualizing the 135 degree
phase diagrams being in quadrature to the 45 degree panels, and the 180
degree phase diagrams being the complete opposite to the 0 degree panels. As
(La Ni˜a) sea surface temperatures (SSTs) in tongue-like structures extend-
ing from the west coast of South America across the equatorial Pacific to the
dateline. Both QB and LF ENSO surface temperature sequences also support
the findings in studies such as White and Tourre (
2003
), which indicate that
such sequences also involve a significant modulation of the evolution of
Indian Ocean SST patterns. Over land in the Northern Hemisphere, surface
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