Jupiter cloud structure from Galileo images: Local cloud systems

D.J. Banfield, M. Bell, P.J. Gierasch, E.A. Ustinov (Cornell), A. Vasavada, A.P. Ingersoll (Caltech), M.J.S. Belton (NOAO), Galileo Imaging Team

A great deal of small scale cloud activity has been observed in Galileo images. The images were taken in two methane bands and a nearby continuum, have a horizontal resolution of about 30 km, and are time lapsed with separations of about 1 hour or 10 hours. One class of small scale activity is typified by clusters of optically thick clouds that cover an area several hundred km across, and have cloud elevation variations of several 10's of km. In one case northwest of the Great Red Spot, the base of the system is at a pressure level exceeding 5 bars, pointing to water as the condensate. These sytems show significant structural evolution during one hour. Another class of system are linear cloud striations, sometimes arranged in parallel rows with separations of a few hundred km. The linear striation is often made up of a series of small puffs, each a few 10's of km in diameter. The height of these systems is about 10 km and they occur at a pressure level of approximately 1 bar. It is speculated that they are ammonia condensation triggered by symmetric instability, and that they are diagnostic of strong vertical shear and low static stability. We have found this type of system to the northeast of the GRS and to the southwest of the observed hotspot.