Mapping potential-vorticity dynamics on Jupiter. I: Zonal-mean circulation from Cassini and Voyager 1 data

Abstract

SUMMARYMaps of Ertel potential vorticity on isentropic surfaces (IPV) and/or quasi-geostrophic potential vorticity (QGPV) are well established in dynamical meteorology as powerful sources of insight into dynamical processes involving 'balanced' flow. In the present study, we derive maps of zonal-mean IPV and QGPV in Jupiter's upper troposphere and lower stratosphere by making use of a combination of velocity measurements, derived from the tracking of cloud features in images from the Voyager 1 and 2 and Cassini missions, and thermal measurements from the Voyager 1 IRIS and Cassini CIRS instruments. IPV and QGPV are mapped and compared for the entire globe between latitudes ±55 • . Profiles of zonally averaged PV show some evidence for a step-like pattern suggestive of local PV homogenization, separated by strong PV gradients in association with eastward jets, though on differing scales in the northern and southern hemispheres. The northward gradient of PV (IPV or QGPV) is found to change sign in several places in each hemisphere, even when baroclinic contributions are taken into account. The relationship of lateral gradients of IPV and QGPV with the corresponding mean zonal flows indicate that the northern hemisphere may be closer to marginal stability with respect to Arnol'd's second stability theorem than the southern hemisphere.

Brightness power spectral distribution and waves in Jupiter's upper cloud and hazes

“…This value agrees with that estimated by Read et al (2006) from direct measurements of the temperature field. Therefore, these two scales fall within the range of wavenumbers encompassed by our power spectra analysis.…”

Saturn Atmospheric Structure and Dynamics

“…Dowling (1995) presented evidence to suggest that Jupiter's atmosphere approached this state of neutral stability with respect to Arnol'd II quite closely. This was subsequently confirmed using fully stratified PV by Read et al (2006a).…”

“…Dowling andIngersoll 1988, 1989) or quasi-geostrophic forms . Most recently, Read et al (2006aRead et al ( ,b, 2009) have combined cloud-tracked velocities and retrievals of temperature and f p from infrared remote sounding to obtain potential vorticity maps and profiles in the upper tropospheres and stratospheres of both Jupiter and Saturn. This approach uses either the large Richardson number approximation to q E ,…”

Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps

“…This would address one shortcoming of our results: a factor-of-almost-2 difference between Saturn's observed weather-layer deformation radius [1000-1500 km for the first baroclinic mode (Read et al 2009)] and the simulated L D2 that produces qualitatively similar polar behavior, which is in the 1800-2800-km range. A first baroclinic deformation radius L D1 in our model is generally twice L D2 , which would be up to 4 times larger than estimates for Saturn.…”