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S. G. Edgington, S. K. Atreya (U. Michigan), L. M. Trafton (U. Texas), J.J. Caldwell (York U.), R. F. Beebe, A. A. Simon (NMSU), R. A. West (JPL)
Ultraviolet spectra (180-230 nm) of Jupiter have been analyzed to determine the height profiles of ammonia and eddy mixing in the troposphere and stratosphere at various latitudes along the central meridian in the northern and southern hemispheres along with the Great Red Spot (GRS). The data were obtained with the Hubble Space Telescope Faint Object Spectrograph (HST/FOS) in May 1992 and June 1993 with an angular resolution of 1". Ammonia and acetylene signatures are unambiguously detected. Beyond 220 nm, a combination of aerosols and Raman scattering is needed to reproduce the spectra. Using a photochemical model, which combines the hydrocarbon, ammonia, and phosphine chemical cycles, and a Rayleigh-Raman radiative transfer model, we have determined self-consistently the altitude profiles of ammonia needed to fit the measured albedos in the 180-220 nm wavelength interval and the eddy mixing required to produce such a distribution. The profiles of ammonia and the eddy mixing are found to vary with latitude and feature. Apparent discrepencies are found between these results and those inferred from IR measurements (Griffith \it et al.\rm, \it Icarus\rm, \bf 98\rm, 82-93, 1992; Lara \it et al.\rm, \it Icarus\rm, \bf 131\rm, 341-357, 1998), if the results of the IR data -- which originate from \ge 240 mbar -- are extrapolated linearly on a log-log scale to lower pressures (\le 150 mbar) from where the UV data orginate. The largest discrepency is in the GRS region. The UV data indicate that ammonia is more abundant above the GRS than over other regions observed with the FOS, in agreement with UV data taken with IUE (Wagener \it et al.\rm, \it Icarus\rm, \bf 66\rm, 188-191, 1986). However, the IR data indicate that the GRS contains either the same or less ammonia as other regions. Possible reasons for these discrepancies are 1.) the extrapolation of the IR profiles to pressure levels \le 150 mbar is invalid and/or 2.) the IR data do not correspond to the same longitudes as the FOS data. Simultaneous measurements and analyses of ultraviolet and infrared data would be highly desirable to resolve discrepencies.
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The author(s) of this abstract have provided an email address for comments about the abstract: sgest@engin.umich.edu