Long-Term Behavior of Tropospheric Temperatures in Jupiter: Evidence for Quasi-Seasonal and Non-Seasonal Variability

Abstract A four-decade study of ground-based mid-infrared observations of Jupiter covering three and a half of its solar orbits over ±30° of latitude has revealed unexpected variations of upper-tropospheric temperatures. Patterns of variability with 10-14 year periods at discrete latitudes were discovered, all within ±2 years of Jupiter’s 11.9-year orbital period. Their repeated pattern of temperature variations is strongly anticorrelated between conjugate latitudes at 16°, 22° and 30° from the equator, latitudes too low to be significantly influenced by seasonal solar forcing. A strong temperature periodicity of 8-9 years is limited to within 10° of the equator. Another periodicity of 7 years covers a wide range of latitudes. A weaker but significant 4-year period covers latitudes from 10°S to 30°N. The 4- and 8-9-year periods at 330 mbars appear to be correlated with those 60-70 km higher in the stratosphere near ~10 mbar, with a ~2-year delay from the stratospheric to the tropospheric level, suggesting a top-down control of tropospheric temperatures by radiative processes in Jupiter’s stratosphere. Correlations between temperature variability and changes in visible appearance of clouds were also detected in Jupiter’s South Equatorial Belt (6°S-17°S) and North Equatorial Belt (6-15°N). No variability was detected at periods longer than 14 years.