The stratosphere consists of about 17% of the mass of Earth's atmosphere and the ozone it contains plays a key role in shielding the surface from harmful ultraviolet radiation. Its composition and patterns of variability are fundamentally distinct from those in the troposphere which govern surface weather and climate. Nonetheless, work in recent decades has shown that variability in the stratosphere can influence the surface in some surprising and important ways. Much of the work in my group seeks to understand this influence and how it can be used to improve weather prediction and projections of climate change.

In this talk I will review some of the evidence for this influence, focusing in particular on surface impacts of stratospheric sudden warmings (SSWs), and will present several recent projects that shed light on the mechanisms responsible. These include a new, minimal dynamical model of the stratospheric polar vortex, a set of general circulation model studies focused on understanding why the surface response is localized over the North Atlantic, and a community intercomparison project focusing on quantifying the effects of the stratosphere on specific ensemble forecasts.