Slantwise Convection on Fluid Planets

Slantwise convection should be ubiquitous in the atmospheres of rapidly rotating fluid planets. Using NASA's Cassini wind observations of Jupiter at the 1-bar level, we first construct toy Jupiter atmospheres and explore potential vorticity as a function of latitude, jet depth and temperature stratification. Richardson number <1 atmospheres are susceptible to transient symmetric instability and ensuing slantwise convection, and the horizontal component of the Coriolis force cannot be neglected in deep atmospheres.

The sole in-situ measurement of a giant planet atmosphere comes from the Galileo probe, which plunged through Jupiter's weather layer at 6.5 degrees N and measured a remarkably stable atmospheric temperature profile. Horizontal winds were observed to substantially increase from 1 to 3 bars, in a region of relatively low static stability. Using geostrophic coordinates developed for terrestrial frontogenesis, we generalize an expression to determine lapse rates along constant angular momentum surfaces for deep atmospheres at any latitude. We show that this high shear region indicates the best possibility of slantwise convection, and suggest that the fluid here is likely adiabatic, in spite of the observed static stability.