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J.A. Magalhaes, A. Seiff (NASA Ames Research Center/SJSUF), R.E. Young (NASA Ames Research Center)
The Galileo Probe Atmospheric Structure Investigation (ASI) provided the first direct measurement of thermal structure below the visible cloud tops of Jupiter. Temperature, pressure, and acceleration were directly measured by sensors during the parachute descent phase, which commenced at about the 0.5 bar pressure level and ended at the 22 bar level. Seiff et al (1998, JGR, Galileo Probe special issue) found the lapse rate to be close to or equal to adiabatic throughout this region, with notable possible deviations from adiabaticity between 0-6 bars and at pressures greater than 16 bars. However, an unexpectedly large range and rate of change of the internal temperature of the Galileo probe during the parachute descent phase led to significant uncertainties in the pressure sensor measurements, which translate into significant uncertainties in the lapse rate and hence static stability. The static stability of Jupiter’s atmosphere below the cloud tops is a fundamental quantity of interest becuase it can have an important influence on the mode of outward heat transport and the dynamics of Jupiter’s atmosphere. Here we report on the use of data from only the temperature sensors and accelerometers, which were weakly influenced by the anomaly in the probe’s internal temperatures, to derive more accurate values of the lapse rate and, in particular, deviations from the adiabatic lapse rate.