Tropospheric and stratospheric aspects of the Arctic oscillation

The role of the stratospheric variability in the Arctic Oscillation (AO) is investigated by selecting 18 large month‐to‐month variation events. It is shown that although tropospheric features are very similar, the vertical structure of the AO differs considerably depending on whether it is initiated by a downward propagation of zonal‐mean zonal wind anomalies from the stratosphere (type S) or it is produced within the troposphere (type T). Type S events preferentially occur during February and March, while type T events are seen during November and December. The results of the analysis suggest that diverse aspects of the AO‐related variability can more easily be understood as coupling and uncoupling of stratospheric and tropospheric modes of variability.