On the response of Stratospheric Sudden Warming to climate forcing

Stratospheric sudden warming (SSW) is one of the most impressive realizations of wave-mean flow interaction in the Earth's atmosphere. It is caused by the breaking of planetary-scale waves that propagate upwards from the troposphere

On the one hand, the probability distributions of the finite amplitude wave activity and zonal mean zonal wind at 10 hPa in winter are skewed, and the differences between SSW and non-SSW years are obvious. However, the vertical component of Eliassen-palm flux at 100 hPa is symmetrically distributed and there's no apparent difference between SSW and non-SSW years. If it is not the vertical component of Eliassen-palm flux giving rise to the skewness, what could it be?

On the other hand, SSWs happen roughly every 2 years. Therefore, it's hard to get a statistically robust analysis since it's time-consuming and resource-expensive to simulate SSWs in GCMs. Currently, the prediction of the long-term trend in the SSW frequency due to climate change is not well constrained among models.

To further study what really controls the probability distribution in the present-day climate and how it will react to future climate forcing, we use an idealized 1D model by forcing the vertical component of Eliassen-palm flux at the bottom to gain a statistically robust analysis in a limited amount of time.

Although people have argued that SSW can occur through the self-tuned resonance of the polar vortex (Plumb, 1981), by studying SSW from the perspective of bottom forcing, we hope to elucidate the influence of climate change on the frequency of SSWs.