than 2 days, play an important role in the annular mode dynamics despite their weak climatological amplitudes]{} [@Kuroda2011].

Annular mode and eddy-jet feedback
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Jet climatology and annular mode structure
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[We]{} will be focusing on the Southern annular mode in the reanalysis data [for simplicity, considering the longitudinal symmetry in the Southern Hemisphere]{}. There are two separate jets in the Southern Hemisphere [climatology]{} (Figure 1a), namely, the subtropical jet centering around 35$^\circ$S and the midlatitude jet at around 50$^\circ$S. [Strictly following LH01, the zonal index is defined as the leading principal component (PC) of $\langle [\mathbf{u}]\rangle$, in which the angle brackets denote vertical average. The leading EOF of $\langle [\mathbf{u}]\rangle$ explains 40$\%$ of the total variance, while the second EOF explains 20$\%$. Here the zonal index is normalized so that its standard deviation is one. The latitude-pressure pattern of $[\mathbf{u}]$ and $[\mathbf{T}]$ associated with the annular mode in the reanalysis data can be seen by regressing $[\mathbf{u}]$ and $[\mathbf{T}]$ on the zonal index at zero-day lag (Figures 1bc). Note that the correlation between the zonal index and the leading PC of $[\mathbf{u}]$ is 0.995, so Figure 1b is essentially equivalent to the leading EOF of $ [\mathbf{u}]$.]{} The anomalous 