Simulations of Deep Jets and Circulation on Giant Planets

(NOTE UNUSUAL DAY AND LOCATION)

Understanding the east-west flows on Jupiter and Saturn has long been a challenge in geophysical fluid dynamics. Jupiter's atmosphere features distinct dynamical regimes: equatorial eastward flows, midlatitude eddy-driven jet streams, and a jet-free turbulent polar region. Saturn shows similar regimes, but lacks evidence for deep midlatitude meridional cells. While both planets have strong equatorial flows, Jupiter's reach ~100 m/s, and Saturn's are three times stronger and twice as wide.

Recent Juno and Cassini gravity measurements revealed that Saturn's zonal jets reach ~9,000 km deep, whereas Jupiter's are ~3,000 km deep. This study presents a new 3D deep anelastic model results, simulating the equatorial and midlatitude jet patterns, consistent with Juno's data. We find that vertical and meridional eddy momentum fluxes are crucial in driving midlatitude circulation. We also explore the parameters affecting the number, extent, strength, and location of midlatitude jets and cells.

At the equator, atmospheric depth is shown to control the strength and latitudinal extent of zonal flows, aligning with observations from Jupiter and Saturn. Our results suggest that atmospheric depth is proportional to the convectively-driven eddy momentum flux, influencing zonal flow strength. These findings offer a mechanistic explanation for the differences between Jupiter's and Saturn's equatorial regions, advancing our understanding of gas giant atmospheres.