On the Interaction of Jupiter’s Great Red Spot and Zonal Jet Streams

Abstract

In this paper, Jupiter's Great Red Spot (GRS) is used to determine properties of the Jovian atmosphere that cannot otherwise be found. These properties include the potential vorticity of the GRS and its neighboring jet streams, the shear imposed on the GRS by the jet streams, and the vertical entropy gradient (i.e., Rossby deformation radius). The cloud cover of the GRS, which is often used to define the GRS's area and aspect ratio, is found to differ significantly from the region of the GRS's potential vorticity anomaly. The westward-going jet stream to the north of the GRS and the eastward-going jet stream to its south are each found to have a large potential vorticity "jump." The jumps have opposite signs, and as a consequence of their interaction with the GRS, the shear imposed on the GRS is reduced. The aspect ratio of the GRS's potential vorticity anomaly depends on the ratio of the imposed shear to the strength of the anomaly. The east-west to north-south aspect ratio is found to be ϳ2:1, but without the opposing jumps it would be much greater. The GRS's high-speed collar and quiescent interior require that the potential vorticity in the interior be approximately half that in the collar. No other persistent geophysical vortex has a significant local minimum of potential vorticity in its interior, and laboratory vortices with such a minimum are unstable.

Jupiter's zonal winds: are they bands of homogenized potential vorticity organized as a monotonic staircase?

“…It is this far-field zonal velocity u ∞ (y), shown in figure 1, in which we are interested in determining whether its PV is in nearly uniform bands with sharp interfaces and whether those bands form monotonic steps. Previous researchers [32,34,35] parametrized the influence of deep layers on the Jovian weather layer with the height h b (y) of the rigid bottom topography. However, it is more useful (but equivalent) for us to use the PV q ∞ (y) of the far-field zonal flow u ∞ (y)x.…”

“…Using the one-and-a-half layer quasi-geostrophic approximation, Van Buskirk [42] and Shetty et al [35] showed that the aspect ratio of a vortex embedded in a shearing zonal flow is primarily a function of the ratio of the magnitude of the PV of the vortex to the shear of the local zonal flow. To a first approximation, the aspect ratio of a vortex that is a steady or uniformly translating solution of the one-and-a-half layer quasi-geostrophic equations behaves as it does for a Moore-Saffman vortex, i.e.…”

Changes in Jupiter’s Great Red Spot (1979–2006) and Oval BA (2000–2006)

“…Previous researchers (Dowling and Ingersoll, 1989;Marcus, 1993;Shetty et al, 2007) parameterized the influence of deep layers on the jovian weather layer with the height h b (y) of the rigid bottom topography. However, it is more convenient (but equivalent) to use the PV q 1 (y) of the far-field zonal flow u 1 ðyÞx.…”

“…The reason for so few trials is due to the computational expense of initial-value codes, which usually take tens of thousands of time steps (with wall-clock times on the order of days) to converge to an approximately steady or self-similar solution for a high spatial resolution code. To find the ''best-fit" parameters with only 100 trials requires intuition (or luck), i.e., finding that the results are nearly independent of some parameter combinations and highly sensitive to others (cf., Shetty et al, 2007). In Shetty et al (2007) we applied inverse methods to the GRS using a ''trait-matching" method with velocity fields extracted from Voyager mosaics to solve the inverse problem.…”

“…To find the ''best-fit" parameters with only 100 trials requires intuition (or luck), i.e., finding that the results are nearly independent of some parameter combinations and highly sensitive to others (cf., Shetty et al, 2007). In Shetty et al (2007) we applied inverse methods to the GRS using a ''trait-matching" method with velocity fields extracted from Voyager mosaics to solve the inverse problem. We found that some properties (i.e., ''traits") of the GRS were sensitive to the values of some parameters and nearly independent of others, and defined the model's ''best-fit" values as those the best reproduced the traits.…”