Dynamics of Jupiter's Atmosphere

Results from the Galileo probe and orbiter arc compared with Voyager and ground-based results. The probe made measurements to the 20-bar level, well below the nominal cloud base at 5 bars and well below the level where sunlight is absorbed. The winds increased with depth within the clouds and then remained constant below cloud base. This rules out most "thin weather layer" models of Jovian meteorology. Water, H_2S, and NH_3 were depleted relative to "solar" abundances at the nominal cloud base but increased with depth below 10 bars. Apparently the probe entered a dry downdraft that penetrated to 20 bars. Consistent with this result, the orbiter found water varying by factors of 100 from place to place, with the lowest values at the sites that resemble the one where the probe went in. The orbiter also revealed that these sites are regions of horizontal convergence of the cloud top winds, which is consistent with the downdraft hypothesis