Thermal structure of Saturn from Voyager infrared measurements: Implications for atmospheric dynamics

Saturn Atmospheric Structure and Dynamics

“…Outside the equatorial region, the albedo pattern at 890 nm is well correlated with the eastward jets and the temperature field at 500 mbar (Fletcher et al 2007a,b): equatorward of the eastward jet peak the haze is bright (high and dense) and the temperatures low, with the contrary occurring on the poleward side (dark band and high temperatures). This suggests that in the upper troposphere and lower stratosphere, ascending motions occur on the equatorward side of the jet peak whereas descending motions occur on the poleward side accompanied by adiabatic cooling and warming, in good agreement with results obtained from the Voyagers (Conrath and Pirraglia 1983). This stands in contrast to the tropospheric continuum cloud top level, where the inferred pattern of rising and sinking motions is just the opposite (Del Genio et al 2007a) and not obviously related to the albedo pattern (see section 7.4.2).…”

“…Conrath and Pirraglia (1983) found that outside the equatorial region, the temperature gradient at 150 mbar in the Voyager IRIS data is anti-correlated with the measured cloud-top zonal wind velocities. The anti-correlation has also been seen in temperatures from Cassini CIRS (Flasar et al 2005).…”

“…In addition to the large scale equator-to-pole temperature gradients, between ~2-300 mbar there are temperature variations of 2-3 K on the scale of the zonal jets. Outside the equatorial region, the temperature gradients are correlated with the mean zonal winds, with warmer temperatures where the winds are cyclonic, and colder temperatures where the winds are anticyclonic (Conrath and Pirraglia 1983;Fletcher et al 2007bFletcher et al , 2008. Temperatures in the equatorial region have been observed to oscillate with a period of ~15 Earth years (Orton et al 2008; section 7.3.7).…”

“…More extensive thermal data was obtained by the infrared spectrometer IRIS on Voyagers 1 and 2. Conrath and Pirraglia (1983) used Voyager IRIS data to obtain meridional temperature profiles at three pressure levels in the upper troposphere just after northern spring equinox. At 150 mbar, they found a hemispheric asymmetry, with the north pole ~5K colder than the equator, but no large-scale gradient in the south.…”

Heat transport in 3D anelastic simulations of the internal dynamics of giant planets without cores

“…Temperatures retrieved by inversion of Voyager infrared spectral measurements. The broken curve is a fit to the northern hemisphere 150-mbar temperatures which has been folded over at the equator to compare with the southern hemisphere (Conrath and Pirraglia 1983). Overlaid is a similar profile in grey for the simulation with no core.…”