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One topic not addressed by our climatology is variability in the east/west location of the PSA pattern. In response to the emergence of central Pacific ENSO events in recent years, some authors have suggested that the PSA pattern moves east/west depending on the precise location of the associated tropical SST anomalies \citep[e.g.][]{Sun2013,Wilson2014,Ciasto2015}. Others suggest that the pattern is relatively stationary \citep[e.g.][]{Liu2007,Ding2012}, however either way the broad region (10$^{\circ}$N to 10$^{\circ}$S in the rotated coordinate system) used by our identification algorithm renders it insensitive to subtle east/west movements. Given that the PSA pattern did not show a strong association with the Ni\~{n}o 3.4 index (an index that is sensitive to both central and eastern Pacific ENSO events), it would be fair to say that even if the location of tropical SSTs does cause the pattern to move slightly, this would represent only a small fraction of all PSA pattern events.   This weak association with ENSO challenges our fundamental understanding of the PSA pattern. The most commonly held view to date is that the pattern is primarily a response to ENSO forcing \citep[e.g.][]{Mo2001} that is moderated by the state of the `atmospheric bridge' (BRIDGE REFS). In particular, the pattern is thought to be most active when ENSO and the SAM are in phase \citep{Fogt2006}. A more comprehensive analysis of the relationship between the pattern and tropical convection would be required to confirm this (e.g. lagged correlations with SSTs and other indicators of tropical convection like the outgoing longwave radiation), but our results suggest that the PSA pattern might be better conceptualized as a preferred regional atmospheric response to various internal and external forcings (i.e. with ENSO being just one of many players). Rather than casting the SAM in a facilitating/bridging role, the strong association identified here is more consistent with the work of \citet{Ding2012}, who suggest that the the SAM (i.e. the leading EOF mode of SH circulation variability) represents the superposition of the PSA pattern in the Pacific sector and a (largely independent) meridional dipole pattern in the Indian Ocean sector. In other words, the SAM and the PSA pattern are closely related because in the Pacific sector they are one and the same phenomenon. In contrast to \citet{Ding2012} our results downplay the association between the SAM / PSA pattern and ENSO, however in an analysis of seasonal timescale data they do note that the PSA pattern appears to be a preferred mode that is very sensitive small variations in tropical convection (a sentiment shared by REF). convection.  Tropical SST forcing is one way to force such variations, but it is not a requirement. requirement and in many cases the PSA pattern appears to be forced by tropical convection that is not associated with the area of highest SST anomaly \citep{Harangozo2004}.  In addition to a more detailed analysis of the relationship between the PSA pattern, tropical convection and the SAM, our new methodology could also be adapted for studies of other quasi-stationary waveforms. The most obvious candidate is the Pacific-North American (PNA) pattern \citep{Wallace1981}, which plays an important role in winter climate variability over the North Pacific and North America \citep[e.g.][]{Notaro2006}. Like its namesake, the PNA pattern follows an approximate great circle path, has traditionally been analyzed via EOF analysis and has been implicated in recent mid-to-high latitude trends \citep[e.g.][]{Ding2014,Liu2015}. Other non-zonal waveforms that do not follow an approximate great circle path would be more challenging, however methods have been developed for applying Fourier analysis to synoptic-scale, non-zonal waveforms \citep{Zimin2006} and may represent a starting point for future research.