Is Enhanced Predictability of the Amundsen Sea Low in Subseasonal to Seasonal Hindcasts Linked to Stratosphere-Troposphere Coupling?

The Amundsen Sea low (ASL) is one of the key components of the Antarctic surface climate. Here, we assess the subseasonal to seasonal (S2S) predictive skill of the ASL in two state-of-the-art forecasting systems based on the anomaly correlation coefficient (ACC). It is found that the ASL predictability during austral spring is higher than in the other seasons with lead times ranging from 1 to 4 weeks. The spring ASL predictability has an ACC of about 0.6 with lead times of 1-2 weeks and about 0.44 with lead times of 3-4 weeks. The enhanced ASL predictability during austral spring is mainly due to the strengthening of stratosphere-troposphere coupling, coincident with a weakened stratospheric polar night jet and increased wave-mean flow interactions in the stratosphere. This study demonstrates that the stratosphere-troposphere coupling provides an important source of predictability for the Antarctic surface weather and climate on S2S timescale.