The Cloud Structure and Morphology of Jovian Equatorial Hot Spots

Sarah T. Stewart Caltech

We present absolutely calibrated full disk images of Jupiter obtained at the NASA Infrared Telescope Facility from June through December, 1996. The data consist of broadband and CVF images from 1.58 to 8.57 microns taken with the NSFCAM and MIRLIN instruments. Our full disk coverage over several months provides an excellent opportunity to study the evolution of 5 micron hot spots and conduct a comparative study between hot spots.

Although hot spots tend to appear at regular longitudes in a wind-shifted frame relative to System III (Ortiz et al., B.A.S.S. 28: 22.05), their individual motion is more complex and can lead to errors in long term tracking of a single feature. While hot spots manifest themselves as semi-permanent features at specific longitudes, the unknown meteorology that creates them distorts the shape and varies the motion of individual spots. Therefore, a direct comparison of a feature at a given longitude may not be applicable on time scales longer than a few weeks. Our observations confirm that an individual hot spot may change significantly in morphology on time scales of weeks. Hot spots are a diverse set of features that range in peak brightness temperature from tex2html_wrap_inline17 244 to tex2html_wrap_inline17 252 Kelvins at 4.78 tex2html_wrap_inline21 m in our images.

Using a single scattering cloud inversion technique developed by Banfield et al. (Icarus 121: 389-410), we uniquely constrain cloud profiles between tex2html_wrap_inline17 10 mbar and tex2html_wrap_inline17 1 bar. We observe two hazy cloud layers over all hot spots peaking at tex2html_wrap_inline17 300 mbar and tex2html_wrap_inline29 20 mbar. We will present constraints on the main cloud level, between 1 and 1.5 bar, employing full anisotropic multiple scattering radiative transfer models of the reflected sunlight and thermal emission.