Signature of the Antarctic oscillation in the northern hemisphere
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Using the ECWMF daily reanalysis data, this paper investigates signatures of the Antarctic Oscillation (AAO) in the upper troposphere of the northern hemisphere. It is found that during boreal winter, a positive (negative) phase of the AAO is associated with anomalous easterlies (westerlies) in middle-low latitudes (~30–40°N) and anomalous westerlies (easterlies) in middle-high latitudes (~45–65°N) of the upper troposphere about 25–40 days later. While there is also a response in zonal wind in the tropics, namely over the central-eastern Pacific, to some extent, these tropical zonal wind anomalies can trigger a Pacific/North American teleconnection patterns (PNA)-like quasi-stationary Rossby waves that propagate into the Northern Hemisphere and gradually evolve into patterns which resemble North Atlantic teleconnection patterns. Furthermore, these quasi-stationary Rossby waves might give rise to anomalous eddy momentum flux convergence and divergence to accelerate anomalous zonal winds in the Northern Hemisphere.
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