Tropopause and lower stratosphere winds and eddy fluxes on Saturn as seen by Cassini imaging

An automated cloud feature tracking algorithm is applied to 2004 Cassini Imaging Science Subsystem images of Saturn's southern hemisphere and equatorial region (5 degrees N-70 degrees S) in continuum, methane band, and ultraviolet filters to derive zonal wind profiles and eddy momentum fluxes from the middle troposphere cloud tops to the lower stratosphere. Zonal winds in the eastward and westward jets decrease in strength from the cloud tops (greater than or similar to 1 bar) to the upper troposphere (similar to 60-600 mb), but do not measurably change in strength from the upper troposphere to the tropopause (similar to 60 mb) to the lower stratosphere (less than or similar to 60 mb). A narrow (similar to 3 degrees N-3 degrees S) equatorial jet is detected at the cloud tops, but a previously reported strengthening of this jet from the cloud top level to the upper troposphere/tropopause region cannot be verified due to an absence of easily trackable features at the equator and conflicting results for the few features available. Eddy momentum fluxes on either side of the jet cores outside the tropics (poleward of similar to 20 degrees S) converge into the eastward jets and diverge from the westward jets. Whether the flux convergence into the eastward jets weakens from the visible cloud level to the upper troposphere cannot be determined for this limited time period, but the eddy convergence appears to increase from the troposphere to the lower stratosphere. The divergence of the eddy flux from the westward jets seems to more clearly increase from the middle to the upper troposphere to the stratosphere, but this does not explain the slight weakening of the westward jets with height.

Automated summary

An study on the wind profiles and eddy momentum fluxes in the clouds of Saturn's southern hemisphere and equatorial region reveals changes in wind speed strength at different altitude levels, as well as convergence and divergence patterns of eddy momentum fluxes around the eastward and westward jets. The study also notes the challenges of verifying the strength of equatorial jets near the equator, as well as the increase in eddy convergence from the troposphere to the lower stratosphere and the divergence of eddy flux from the middle to the upper troposphere and stratosphere.