Be the first to like this
Saturn’s polar stratosphere exhibits the seasonal growth and dissipation of broad, warm
vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter.
The longevity of the exploration of the Saturn system by Cassini allows the use of infrared
spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region
of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We
constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres.
Although the NPSV formed during late northern spring, by the end of Cassini’s
reconnaissance (shortly after northern summer solstice), it still did not display the contrasts
in temperature and composition that were evident at the south pole during southern summer.
The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near
78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible
for Saturn’s long-lived polar hexagon—which was previously expected to be trapped in the
troposphere—can influence the stratospheric temperatures some 300 km above Saturn’s