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Session 27 - Planets.
Oral session, Wednesday, January 07
Using the Hubble Space Telescope (HST) we have obtained global data of Jupiter over a two-year timespan from July 1994 to October 1996. The resolution of the HST Planetary Camera ( 175 km/pixel) allows us to measure the sizes, drift rates and interactions of over two dozen long-lived vortices in the southern hemisphere, including the Great Red Spot, the three White Ovals, and several smaller anticyclones and cyclones. A key question is whether the atmosphere's vertical structure is homogeneous or heterogeneous. In particular, the presence or absence of water clouds has a direct effect on static stability and on the atmosphere's radius of deformation (vortex-interaction distance). Data at 7 deg N latitude from the Galileo Entry Probe indicate a dry atmosphere, whereas recent data from the Galileo Orbiter Photopolarimeter-Radiometer suggest otherwise. We are using the Explicit Planetary Isentropic- Coordinate (EPIC) atmospheric model (Dowling et al. 1998, Icarus, in press) to test the effects of heterogeneity on vortex interactions. The EPIC model integrates the nonlinear, primitive, hydrostatic equations with entropy (potential temperature) as the vertical coordinate. The lower boundary condition is an adiabatic abyssal layer, corresponding to Jupiter's convecting interior, with provision made for the deep-seated circulation. We are studying a range of temperature profiles (dry vs. moist) and variations of the zonal-wind profile with respect to height to determine what is necessary to reproduce the HST observations.
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