Multiscale energy conversion and transfer in the middle atmosphere during the 2023 sudden stratospheric warming
image: Typical multiscale energy cycles during precursor, cooling, and decay stages. Arrows indicate energy transfer directions and thickness represents magnitude.
Credit: Beijing Zhongke Journal Publishing Co. Ltd.
A sudden stratospheric warming (SSW) is a dramatic event in which the polar stratosphere warms by tens of degrees within days, often reversing the high-altitude winds. These events can affect weather patterns and even the mesosphere, the layer above the stratosphere. However, how energy moves across different altitudes and scales during an SSW has remained unclear.
In a new study published in Earth and Planetary Physics, XiaoQi Wu and colleagues at Beijing Normal University applied a sophisticated analysis framework—the multiscale window transform (MWT) and its associated localized energetics analysis (MS-ECT)—to dissect the 2023 major SSW. They used NASA’s MERRA-2 reanalysis data to reconstruct atmospheric fields into three scale windows: large-scale (>64 days), SSW-scale (8–64 days), and synoptic-scale (<8 days).
The results reveal that pressure flux (the work done by pressure forces) plays a critical role in vertically coupling the mesosphere and stratosphere, enabling energy exchange between these two regions. For the first time, the team quantified cross-scale energy transfers. They found that the canonical transfer of available potential energy (APE) consistently flows from the large-scale window to the SSW-scale window in both the stratosphere and mesosphere—a signature of baroclinic instability, a key mechanism driving atmospheric waves.
Comparing the 2023 event with the 2012–2013 SSW, the researchers found that baroclinic instability was active in both events, confirming its robust role. However, the 2023 SSW exhibited significantly stronger energy transfer magnitudes in the mesosphere, likely linked to a larger temperature increase (~70 K vs. ~40 K). The study also showed that kinetic energy often propagates downward before the SSW, and that the reversal of zonal winds in the mesosphere is associated with energy exchanges across scales.
These findings provide a clearer picture of how energy is redistributed vertically and across scales during SSWs, improving our understanding of stratosphere–mesosphere coupling. The authors note that future work with higher-resolution models and direct observations will help refine these energy pathways, especially in the upper mesosphere where reanalysis uncertainties grow.
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Multiscale energy conversion and transfer in the middle atmosphere during the 2023 sudden stratospheric warming