Disruption of Saturn's quasi-periodic equatorial oscillation by the great northern storm
Publication date: 24 October 2017
Authors: Fletcher, L.N., et al.
Journal: Nature Astronomy
Volume: 1
Issue: 11
Page: 765-770
Year: 2017
Copyright: © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved
The equatorial middle atmospheres of the Earth, Jupiter and Saturn all exhibit a remarkably similar phenomenon–a vertical, cyclic pattern of alternating temperatures and zonal (east–west) wind regimes that propagate slowly downwards with a well-defined multi-year period. Earth's quasi-biennial oscillation (QBO) (observed in the lower stratospheric winds with an average period of 28 months) is one of the most regular, repeatable cycles exhibited by our climate system, and yet recent work has shown that this regularity can be disrupted by events occurring far away from the equatorial region, an example of a phenomenon known as atmospheric teleconnection. Here, we reveal that Saturn's equatorial quasi-periodic oscillation (QPO) (with an ~15-year period) can also be dramatically perturbed. An intense springtime storm erupted at Saturn's northern mid-latitudes in December 2010, spawning a gigantic hot vortex in the stratosphere at 40° N that persisted for three years. Far from the storm, the Cassini temperature measurements showed a dramatic ~10 K cooling in the 0.5–5 mbar range across the entire equatorial region, disrupting the regular QPO pattern and significantly altering the middle-atmospheric wind structure, suggesting an injection of westward momentum into the equatorial wind system from waves generated by the northern storm. Hence, as on Earth, meteorological activity at mid-latitudes can have a profound effect on the regular atmospheric cycles in Saturn's tropics, demonstrating that waves can provide horizontal teleconnections between the phenomena shaping the middle atmospheres of giant planets.
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