Life cycle of sudden stratospheric warming

The composite evolution of the atmospheric flow throughout the stratosphere and troposphere during sudden stratospheric warming events (SSWs) was examined. It was found that as the SSW matures, both the largest stratospheric zonal flow anomalies and the region of largest wave driving descend throughout the depth of the stratosphere. When the anomalous wave driving reached the lowermost stratosphere, the associated flow anomalies appeared to penetrate the tropopause, eliciting substantial anomalous responses in both wave propagation and the mean meridional flow at tropospheric levels. The connection between the stratosphere and the troposphere was amplified by the projection of the descending flow anomalies onto the tropospheric Northern Hemisphere annular mode.