224
Chapter 12: TeJeconnections Patterns
automaticaIly limits the investigation to the portion of variance that is crosscorrelated. The method does not give any information on the importance of
these patterns for the portion of the Z500 variance that is not correlated with
the SST variance.
An example of a direct SVD analysis is shown in Figure 12.4, from WaIlace
et al. (1992). Here the heterogenous correlation maps for the first pattern
resulting from a SVD analysis of the North Pacific SST and the Z500 geopotential field are shown. This pattern explains 52% of the cross-covariance
and the time correlation between the two time-series is 0.81. The mode show
that when SST anomalies in a large area in the North Pacific are connected
with a complex system of anomalies extending weIl into the East Atlantic.
The atmospheric pattern is reminiscent of the PNA telelconnections found
by WaIlace and Gutzier (1981) and the teleconnection pattern induceed by
equatorial SST (Horel and WaIlace, 1981). The interesting result is it seems
that also mid-Iatitudes SST can generate PNA-like structures.
12.4 Concluding Remarks
The pattern identification techniques that have been described are powerful ways to identify systematic mo des of variations and they have greatly
enhanced our understanding of the climate sytem. In fact they are so intriguing and powerful that there is the danger sometimes to forget that the
beautiful wave-like pattern found, for instance in correlation maps, are just
that, maps 0/ correlation coefficients, and they are not physical wave-like
phenomena. It must always be kept in mind that this pattern are expression
of statistical relation that can be conveniently displayed over a geographic
map, but they may or may not correspond to waves in the physical space.
They are pointers to some unknown underlying physical mechanism that is
responsible for the relations between fields that so gracefuIly emerge as teleconnections, but after so much time and effort there is still no convincing
comprehensive dynamical explanation for the teleconnection patterns.
Chapter 12: TeJeconnections Patterns
automaticaIly limits the investigation to the portion of variance that is crosscorrelated. The method does not give any information on the importance of
these patterns for the portion of the Z500 variance that is not correlated with
the SST variance.
An example of a direct SVD analysis is shown in Figure 12.4, from WaIlace
et al. (1992). Here the heterogenous correlation maps for the first pattern
resulting from a SVD analysis of the North Pacific SST and the Z500 geopotential field are shown. This pattern explains 52% of the cross-covariance
and the time correlation between the two time-series is 0.81. The mode show
that when SST anomalies in a large area in the North Pacific are connected
with a complex system of anomalies extending weIl into the East Atlantic.
The atmospheric pattern is reminiscent of the PNA telelconnections found
by WaIlace and Gutzier (1981) and the teleconnection pattern induceed by
equatorial SST (Horel and WaIlace, 1981). The interesting result is it seems
that also mid-Iatitudes SST can generate PNA-like structures.
12.4 Concluding Remarks
The pattern identification techniques that have been described are powerful ways to identify systematic mo des of variations and they have greatly
enhanced our understanding of the climate sytem. In fact they are so intriguing and powerful that there is the danger sometimes to forget that the
beautiful wave-like pattern found, for instance in correlation maps, are just
that, maps 0/ correlation coefficients, and they are not physical wave-like
phenomena. It must always be kept in mind that this pattern are expression
of statistical relation that can be conveniently displayed over a geographic
map, but they may or may not correspond to waves in the physical space.
They are pointers to some unknown underlying physical mechanism that is
responsible for the relations between fields that so gracefuIly emerge as teleconnections, but after so much time and effort there is still no convincing
comprehensive dynamical explanation for the teleconnection patterns.