Other
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p51f1180s&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P51F-1180
Other
[0343] Atmospheric Composition And Structure / Planetary Atmospheres, [3346] Atmospheric Processes / Planetary Meteorology, [5704] Planetary Sciences: Fluid Planets / Atmospheres, [5739] Planetary Sciences: Fluid Planets / Meteorology
Scientific paper
We study the processes that cause meandering of an unstable atmospheric zonal jet. Saturn has two meandering jet streams at 47 and 77 degree N planetographic latitude, where the jets are associated with wavy cloud features called the ribbon and the hexagon, respectively. Spacecraft observations suggest that these jets are in two separate regimes of meandering. The ribbon jet traces a meandering path that propagates in the downstream direction and its shape changes on timescales as short as several Saturnian rotations. In addition, its spatial oscillation’s wavenumber spectrum has no single dominant mode (Sromovsky et al., 1983, JGR). On the other hand, the hexagon is stationary with respect to the planetary rotation rate measured by the Voyagers, and its six-sided structure has remained unchanged since 1980 (Godfrey, 1988, Icarus; Baines et al., in press at P&SS). Past studies of meandering ocean currents and our recent numerical investigation of the ribbon jet (Sayanagi et al., submitted to J. Atmos. Sci.) found that meandering jets can emerge from nonlinear saturation of shear instabilities in an unstable jet. These investigations have linked meandering jets to shear instabilities; however, to the best of our knowledge, a systematic process study of the saturation process is yet to be conducted. Using idealized numerical models, our present investigation systematically analyzes the emergence of meandering jets for a range of planetary beta-effect magnitudes and zonal jet profiles to understand what mechanisms set apart the dynamic and stationary regimes exemplified by the ribbon and the hexagon on Saturn. We use the EPIC atmosphere model (Dowling et al, 1998, 2006) to perform our simulations. Our study is supported by the Cassini project.
Ingersoll P. A. P. A.
Sayanagi Kunio Max
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