Investigating the predictability of Stratospheric Sudden Warmings in the Northern Hemisphere

Understanding of the dynamics of troposphere-stratosphere coupling is important particularly in the context of a stratospheric influence on surface weather patterns and climate. A phenomenon that may demonstrate this two-way vertical link between the troposphere and stratosphere are Stratospheric Sudden Warmings (SSWs). Upward propagating planetary waves are generally believed to be the cause of these events and there is increasing interest in the connection between the state of the stratosphere during a SSW event and the subsequent state of the troposphere. Such a connection implies that improved predictability of SSWs may lead to improved tropospheric predictability on the monthly to seasonal timescale.

This study investigates the predictability of such warmings by running forecasts from different initial conditions prior to their onset in the Northern Hemisphere. The SSWs used in this study were chosen due to the disturbed state of the stratosphere prior to the warming which is believed to make the events more difficult to capture effectively in models. The ability therefore to predict such complicated scenarios could be useful in enhancing seasonal weather predictability.