Constraining the depth of Saturn's zonal winds by measuring thermal and gravitational signals

Upcoming Cassini gravitational measurements can further constrain the penetration depth of zonal winds, as gravitational zonal harmonics associated with deep zonal winds are much larger than those associated with shallow zonal winds. The even gravitational zonal harmonics associated with zonal winds that penetrate to megabar levels start to become distinguishable from the planetary solid body rotation at zonal harmonic degree n≳8. The low-order odd gravitational zonal harmonics, which do not depend on the planetary solid body rotation, will be detectable within likely Cassini measurement errors for cutoff radii rc≲0.98RS (≳1000 bar). Combining thermal and gravitational signals of the zonal winds, the penetration depths of the zonal winds relative to different rotation rates can thus be constrained.