Dynamical implications of Jupiter's tropospheric ammonia abundance

Intermittent cumulonimbus activity breaking the three-layer cloud structure of Jupiter

“…This is a feature which has been difficult to explain by the approaches taken in previous studies [de Pater et al, 2001;Gibson et al, 2005;Showman and de Pater, 2005]. Our calculations explain the observed low NH 3 abundance as being the result of vertical mixing of NH 3 -poor air caused by condensation.…”

Saturn Atmospheric Structure and Dynamics

“…Moist adiabatic ascent, radiative cooling aloft, and compensating dry adiabatic descent produce a reversal of the meridional temperature gradient between the water cloud level and the upper troposphere, such that cyclonic regions are cool and anti-cyclonic regions warm near the water cloud base while the opposite is true near and above the visible clouds (Showman and de Pater 2005). Between the water condensation level and the level of reversal of dT/dy, zonal winds should strengthen with height according to the thermal wind equation.…”

“…However, deep moist convection, which occurs overwhelmingly in the presence of low-level convergence and large-scale mean rising motion, was observed by Galileo and Cassini (during its Jupiter flyby) to be restricted to the belts (Gierasch et al 2000;Porco et al 2003), leading Ingersoll et al (2000 to suggest that the belts are actually the seat of net rising motion. This picture is supported by Jupiter's belt-zone ammonia distribution at 1-5 bars (Showman and de Pater 2005). On the other hand, if Saturn had been the only giant planet the Hadley cell analogy might never have been considered, since the albedo-wind shear correlation breaks down there (section 7.3.2).…”

“…Other less dramatic examples are found preferentially in the cyclonic shear regions and at times in the vicinity of the eastward jets, but almost never in regions of anti-cyclonic shear (Del Genio et al 2007a). This suggests that anti-cyclonic shear regions might be analogous to Earth's subtropics, dominated by large-scale subsidence with possibly an inversion layer of stable temperature and dry air at depth that suppresses vertical development of storms (e.g., Del Genio and McGrattan 1990; Showman and de Pater 2005), while the cyclonic shear regions are areas of net large-scale upwelling at depth.…”

“…The deep-seated meridional temperature gradient that drives the baroclinic instability in this picture comes from the moist convection itself (Lian and Showman 2009). Assuming a near-moist adiabatic lapse rate in the cyclonic regions, subsidence along a steeper dry adiabat in the anti-cyclonic regions would suppress deep convection and lead to a warm temperature inversion just above the water condensation level (Showman and de Pater 2005). Temperatures just above cloud base would be lower, but moisture greater, in the convergent cyclonic regions, creating baroclinically unstable conditions between the two.…”