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Fig. 2


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Left panels: Raw geopotential height data series at the 700 hPa level averaged over 70°–90° S for the period 1968–2020 (top panel), and the FT surrogate (bottom panel). Middle panels: Autocorrelation function of the raw (top) and FT surrogate (bottom) geopotential height data. Right panel: Power spectrum of the raw data (blue) and the FT surrogate (red). As can be seen, there is an identical match for the autocorrelation and the power spectrum.

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