A Study of the Time Variability of Jupiter's Atmospheric Structure

Jupiter's South Equatorial Belt (SEB) underwent a dramatic increase in reflectivity in June/July 1989. The Equatorial Zone (EZ) decreased in reflectivity slightly throughout 1988-1989. Four nights of photometrically calibrated CCD images of Jupiter obtained throughout the period of SEB and EZ activity have been used to construct vertically inhomogeneous atmospheric structure models. These models were constructed to match the center-to-limb behavior of constant-latitude scans obtained from images taken in broadband blue and red/near IR continuum and methane bands. The vertical structure models allow direct quantitative comparison between different latitudinal regions and, more importantly, between different epochs. It was found that the dramatic increase in the SEB reflectivity can be explained with an increase in both the optical thickness (from τ = 3 ± 1 to 5 ± 1) and the single scattering albedo of the upper tropospheric cloud (from ω¯ ₀ = 0.980 ± 0.001 to 0.997 ± 0.001 in the blue). For the EZ, the rate of decrease in reflectivity has been very subtle. A small decrease in the single scattering albedo is detected (from ω¯ ₀ = 0.994 ± 0.001 to 0.992 ± 0.001 in the blue) and a slight change in the optical depth of the upper tropospheric cloud may be detected (from τ = 5 ± 1 to 4 ± 1). No significant change in the pressure levels of the clouds for either of the latitude regions is required to adequately fit the data.