Long-Term Time Variability of Temperature, Gas Abundance and Cloud Fields in Jupiter from Thermal Emission Observations
Tuesday, 16 December 2014
Mid-infrared raster-scans and 2D images of Jupiter’s thermal emission in discrete filters between 4.8 and 24.5 μm have been have covered nearly 2 Jovian years, enabling time-domain studies of its temperature field, minor-constituent distribution and cloud properties. The behavior of stratospheric (~10-mbar) and tropospheric (~100-400 mbar) temperatures is generally consistent with predictions of seasonal variability. These also appear to be long-term periodicities of tropospheric temperatures, with meridionally dependent amplitudes, phases and periods. Temperatures near and south of the equator vary least. There were no variations of zonal mean temperatures associated with any of the “global upheaval” or the corresponding “revival” events that have produced dramatic changes of Jupiter’s visible appearance and cloud cover, although there are colder discrete regions associated with the updraft events that marked the early stages of revivals. Changes visible albedo are accompanied by increases in cloudiness at 700 mbar and higher pressures, together with the mixing ratio of NH3 gas. In contrast to all these changes, the meridional distribution of the 240-mbar para-H2 fraction appears to be time-invariant. Jupiter also exhibits prominent temperature waves in both the upper troposphere and stratosphere that move slowly retrograde in System III. Unlike Saturn’s slowly moving waves, these waves are ubiquitous at certain latitudes and at all longitudes therein. The time scale for coherence of these waves is somewhere between a few days and 4 weeks. These waves are consistent with convectively generated Rossby waves.