Coupled planetary wave dynamics in the polar stratosphere analyzed with potential enstrophy and eddy energy budgets

Anomalies in the stratospheric polar vortex (SPV), such as sudden stratospheric warming (SSW) events, significantly impact surface weather patterns. While the general influence of SSWs on the troposphere is robust, individual events exhibit large variability, partly due to the substantial difference in dynamics and SPV evolution across events. Understanding the physical processes driving SSWs is therefore essential. In this study, we investigate SPV dynamics, focusing on non-linear coupling between planetary wave modes.
We use potential enstrophy and eddy total energy budget analyses to quantify the contributions of different physical processes to SPV evolution. Applying this framework to both an idealized simulation and reanalysis data of the 2003 SSW event, we find that non-linear wave–wave interactions play a crucial role. In the idealized simulation, wave-2 structures emerge in the stratosphere without a prescribed wave-2 source, attributed to non-linear transfer of enstrophy and energy from wave-1 to wave-2. In the 2003 case study, interactions between wave-1 and wave-2 contribute to the transition from a displacement to a split structure. We also find indications of quasi-linear coupling and upscale enstrophy fluxes from wave-2 to wave-1 during this period.
Our findings highlight the significant impact of non-linear wave–wave interactions in transitioning the SPV between configurations. These complex interactions contribute to the uniqueness of each SSW event and may help explain the variability observed across different SSWs.