ClimaTea Lecture

Speaker: Morgan O'Neill

Title: "Slantwise convection on fluid planets: Implications for Galileo and Juno observations at Jupiter"

Abstract: Slantwise convection should be ubiquitous in the atmospheres of rapidly rotating fluid planets. I will argue that convectively-adjusted lapse rates should be interpreted along constant angular momentum surfaces instead of lines parallel to the local gravity vector. Using NASA's Cassini wind observations of Jupiter and a range of jet depths and plausible lapse rates, we first construct toy atmospheres and explore potential vorticity as a function of latitude and Richardson number. The sole in-situ measurement of a giant planet weather layer available for constraining our toy atmospheres comes from the Galileo probe. The probe plunged through Jupiter's weather layer and measured a remarkably stable atmospheric temperature profile. The stability was a surprise to many and various subsequent explanations invoke complicated local flows. I will show that the measured lapse rate does not accurately reflect the influence of convection, and the weather layer is in fact likely neutrally stable. Using lessons from studies of terrestrial frontogenesis, we provide a modified temperature profile that is measured along angular momentum surfaces instead. This new interpretation, which as a function of latitude is most different in the equatorial region, will significantly improve analysis of the ongoing Jovian microwave measurements by NASA's Juno spacecraft.