Stratospheric influence on tropospheric jet streams, storm tracks and surface weather

Abstract

A powerful influence on the weather that we experience on the ground can be exerted by the stratosphere. This highly stratified layer of Earth's atmosphere is found 10 to 50 kilometres above the surface and therefore above the weather systems that develop in the troposphere, the lowest layer of the atmosphere. The troposphere is dynamically coupled to fluctuations in the speed of the circumpolar westerly jet that forms in the winter stratosphere: a strengthening circumpolar jet causes a poleward shift in the storm tracks and tropospheric jet stream, whereas a weakening jet causes a shift towards the equator. Following a weakening of the stratospheric jet, impacts on the surface weather include a higher likelihood of extremely low temperature over northern Europe and the eastern USA. Eddy feedbacks in the troposphere amplify the surface impacts, but the mechanisms underlying these dynamics are not fully understood. The same dynamical relationships act at very different timescales, ranging from daily variations to longer-term climate trends, suggesting a single unifying mechanism across timescales. Ultimately, an improved understanding of the dynamical links between the stratosphere and troposphere is expected to lead to improved confidence in both long-range weather forecasts and climate change projections.

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Figure 1: Persistence of circulation anomalies.
Figure 2: Northern Hemisphere stratosphere–troposphere coupling across timescales.
Figure 3: Southern Hemisphere stratosphere–troposphere coupling.
Figure 4: Surface temperature anomalies.
Figure 5: Ocean response.

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Acknowledgements

J.K. was partly supported by the Australian Research Council Discovery Early Career Research Award ARC DE120102645, and the Australian Research Council Centre of Excellence in Climate System Science. The work of A.A.S., S.C.H. and N.B. was supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). All the authors thank E. Gerber for his thought-provoking and constructive comments on earlier versions of the manuscript. The generous assistance of S. Osprey and S. Ineson with the redrawing of Figs 1 and 2, respectively, is gratefully acknowledged. Thanks also to J. Arblaster, C. Cagnazzo, M. Machin, T. Reichler, and D. Thompson.

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J.K. and A.A.S. created the schematic of stratosphere–troposphere coupling processes, all authors contributed to writing the manuscript.

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Correspondence to Neal Butchart.

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Kidston, J., Scaife, A., Hardiman, S. et al. Stratospheric influence on tropospheric jet streams, storm tracks and surface weather. Nature Geosci 8, 433–440 (2015). https://doi.org/10.1038/ngeo2424

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