This is puzzling:
“This temperature and zonal wind structure resembles those of Earth’s quasi-biennial oscillation (QBO) and Jupiter’s quasiquadrennial oscillation (QQO), in which temperature anomalies and eastward/westward winds alternate in altitude”
Fouchet, T., et al. “An equatorial oscillation in Saturn’s middle atmosphere.” Nature 453.7192 (2008): 200.
And recently the final results of the Cassini spacecraft mission were in the news:
“The density wave is generated by the gravitational pull of Saturn’s moon Janus.”
Wild! Cassini Probe Spots Weird Waves in Saturn’s Rings September 11, 2017 https://www.space.com/38114-weird-waves-saturn-rings-cassini-photo.html
But no one in the research literature has made the connection of the moon’s orbit to the dynamics of the QBO.
From Fouchet et al, again
On Earth, the alternating wind regimes repeat at intervals that vary from 22 to 34 months, with an average period of about 28 months. On Jupiter, the equatorial stratospheric temperature exhibits a 4.4-year period and the equatorial zonal winds in the upper troposphere oscillate with a 4.5-year period. Long-term ground-based monitoring reveals a period of 14.7±0.9 terrestrial years on Saturn. The observational similarities between Saturn’s oscillation and the QBO and QQO are the strong equatorial confinement of temperature minima and maxima and associated shear layers, a stronger eastward than westward shear layer, and the bounding of the equatorial oscillation at latitudes 15–20° north and south. Temperatures near these latitudes are relatively high when equatorial temperatures are relatively low, and vice versa.
On Earth and Jupiter, the quasi-periodic oscillations are triggered by the interaction between upwardly propagating waves and the mean zonal flow.
Both Jupiter and Saturn have 4 significant moons,making the collective lunar orbit difficult to describe. It’s possible that Saturn’s and Jupiter’s “QBO” are more like the Earth’s upper stratosphere oscillations, which align to the semiannual period (0.5 year period). This is suggestive as the values for Jupiter and Saturn’s “QBO” period are closer to 1/2 the planet’s full calendar year period, as show below
|Planet||“year” length||“QBO” period||“QBO upper” period|
|Earth||1 year||2.37 years||0.5 year|
|Saturn||29.46 years||14.7±0.9 years|
|Jupiter||11.86 years||4.5 years|