Abstract: The winter stratosphere is dominated by a strong cyclonic vortex which encircles the pole, acting to confine cold air to high latitudes. In about 2/3 of winters this vortex breaks down in an event known as a sudden stratospheric warming (SSW). Research over the past two decades has established a link between SSWs and surface weather, such as an increased likelihood of extreme cold events over North America and Northern Europe. However, significant uncertainties remain in understanding the dynamics of SSWs and their surface influence.
In this talk, observational and modeling data are used to investigate two classes of SSWs; vortex splits and displacements. In many studies no distinction is made between these events, but they are shown to exhibit very different dynamical behavior. Different surface anomalies following spits and displacements are used to inform the mechanism by which the stratosphere influences the troposphere, and implications for seasonal weather prediction discussed.