Seasonal Prediction Skill of Northern Extratropical Surface Temperature Driven by the Stratosphere

Variability arising from interactions between the tropical oceans and troposphere, particularly the El Niño and Southern Oscillation (ENSO), provides a key source of seasonal predictability to many areas of the world, yet much of the Northern Hemisphere extra-tropics show limited connection to ENSO. However, fluctuations of the stratospheric polar vortex influence extra-tropical surface climate through stratosphere-troposphere coupling, and provide a potential source of predictability. Here, we explore the role of the stratosphere as a source of seasonal predictability of surface climate over Northern Hemisphere extra-tropics both in observations and climate model predictions. We demonstrate that year-to-year variations of the extra-tropical stratosphere play an important role in skillful seasonal prediction of Northern Hemisphere extra-tropical near surface land temperature in boreal spring, and further show that this arises from skillful predictions of the Arctic Oscillation (AO). We establish realistic dynamical connections between the stratospheric polar vortex and the AO for both the observations and model predictions.