Oscillations and teleconnections - The Global Climate System: Patterns, Processes, and Teleconnections - page 46

(Figure 2.9 (Plat e 3 ) zero phase). The latter signal also has a stronger imprint
on SSTs over the Atlantic sector, as detailed in Chang et al.( 1997 ), and
additional impacts on Indian Ocean SST structures. The presence of strong,
out-of-phase tropical and South Atlantic SSTs is seen only in this sequence.
The Eurasian surface temperature pattern is again one of higher latitude
responses as seen with the LF ENSO sequence, but is not as clearly defined.
Over North America there is evidence of a zonal, rather than a meridional,
surface temperature gradient.
In the quasi-decadal band, the MSLP pattern in Figure 2.9 (Plate 3 ) is
suggestive of a westwardly displaced NAO-like structure in the North
Atlantic similar to that seen in the LF ENSO sequence in Figure 2.8 (Plate 2 ) .
Overall, the SO pattern is much less clearly defined than in the QB or LF ENSO
sequences. A strong high-latitude North Pacific MSLP node is seen to dominate
the Pacific sector, with poor definition of the ''classical'' southeastern Pacific
node of the SO. There is also evidence of a distinct MSLP node in the South
Atlantic, which is not seen in the other sequences of higher frequency signals.
Precipitation patterns in the quasi-decadal sequence (Figure 2.9 (Plate 3 ) )
show marked responses over central-western states of the USA, Labrador in
eastern Canada, the Caribbean, southern South America, the UK, western to
central Europe, China and Japan, the Indian subcontinent, Sahelian Africa,
and central to southern Africa. This encompasses regions experiencing both
QB and LF ENSO impacts, and areas where no distinct precipitation
responses to ENSO are found. Taken together, MSLP, surface temperature,
and precipitation responses suggest that there is a pattern of teleconnections
associated with the quasi-decadal signal that has some variations to those
linked to QB and LF ENSO events.
The MSLP and surface temperature signals display the type of global
propagation of co-varying features that are detailed in White and Tourre
( 2003 ). By the very nature of its lower frequency, the quasi-decadal sequence
(Figure 2.9 (Plate 3 ) ) evolves more slowly than the LF ENSO sequence
(Figure 2.8 ( Plate 2 ) ), and in turn this signal evolves more slowly than the
QB sequence (Figure 2.7 (Plate 1 ) ). However, there are still questions as to
whether this is a real wave-like feature or simply reflects differing responses
of each ocean basin to QB, LF, and quasi-decadal signals. These concerns
now need to be seen in the light of the evolution and apparent coherent
propagation of co-varying MSLP and surface temperature features over
both the oceans and land masses.
In the QB sequence (Figure 2.7 (Plate 1 ) ), a coherent MSLP signal evolves
and propagates from the southern Pacific into the North Atlantic between the
0 and 90 degree phase snapshots. This feature then forms part of a distinct
NAO pattern with an underlying SST tripole pattern in the North Atlantic
Ocean as seen in Rodwell and Folland ( 2002 ), and other studies. Over the