The Role of the Stratosphere in Global Predictability across Time and Length Scales (Invited Presentation)

While the stratosphere has long been known to be influenced by tropospheric processes, it is now also understood to exert a downward influence. However, this connection varies strongly in the timing, duration, and location of the interaction. Overall, the longer persistence of stratospheric anomalies as compared to the troposphere has led to the increased use of the stratosphere as a potential source of predictability from sub-seasonal to decadal timescales, and it also plays a role in the changing climate. However, the role of the stratosphere in global predictability has not yet been fully quantified. In fact, the predictability of the stratosphere itself is highly variable with respect to season and location: While the tropical stratosphere is predictable out to several months, the extratropical stratosphere has much shorter lead times of a few days, while there exists statistical predictability for stratospheric extreme events in the extratropics several months in advance. Understanding the predictability and variability of the stratosphere itself will allow for a better quantification of predictability arising from stratospheric processes. This contribution will provide an overview of the state-of-the-art of the currently available prediction skill arising from the coupling between the troposphere and the stratosphere.