The Antarctic Oscillation Structure in an AOGCM with Interactive Stratospheric Ozone
Annular modes. Principal component analysis (PCA) at z500. Leading mode of variability (PC1) in COUP, REF, and ERA-40 data. Name of the mode (AO/AAO) and explained variances are given in brackets. Left: JJA, SH. Right panels: DJF, NH. (a) COUP (AAO, 25.8%). (b) COUP (AO, 16.9%). (c) REF (AAO, 24.0%). (d) REF (AO, 19.7%). (e) ERA-40 (AAO, 22.5%). (f) ERA-40 (AO, 18.4%). For each dataset, sequences of 8 high- and low-index years (red/blue frames) were chosen as sample periods.