A Dynamical Study of Jupiter's Great Red Spot

Citation

Dowling, Timothy Edward (1989) A Dynamical Study of Jupiter's Great Red Spot. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/whc3-mh91. https://resolver.caltech.edu/CaltechETD:etd-05302007-084208

Abstract

This work is presented in the form of two related papers. In the first paper we investigate layer thickness variations in Jupiter's atmosphere by tracking absolute vorticity (ζ + f) along streamlines of the Great Red Spot (GRS) and White Oval BC. The ratio of absolute vorticity to layer thickness, called the potential vorticity, is conserved following the motion. By observing Lagrangian variations of absolute vorticity, we may infer variations in layer thickness. The data thus obtained are a useful diagnostic that will help differentiate between models of Jovian vortices. We interpret the observed layer thickness variations using a simple "1-1/2" layer model in which a thin upper weather layer, which contains the vortices, overlies a much deeper layer, which is meant to model the deep atmosphere. In this model, layer thickness variations are directly coupled to motions in the deep atmosphere, and we use the data to infer the deep motions. In the first paper we interpret the data, using the quasi-geostrophic equations. In the second paper we reinterpret the data, using the more general shallow water equations. Most current models of the GRS are cast in terms of the 1-1/2 layer model, and they start by prescribing the motions in the deep atmosphere. Here we are able to derive the deep motions using the same 1-1/2 layer model assumptions, up to a constant that depends on the unknown static stability of Jupiter's troposphere. None of the current prescriptions for the deep motions are in qualitative agreement with the observations over the full range of latitudes observed. We study the 1-1/2 layer model numerically, using both the derived deep motions and the prescribed deep motions of current models. Only the present model, based on observations, yields Lagrangian absolute vorticity profiles that agree with those obtained in the first paper. A model run that starts with the observed zonally averaged cloud-top winds and derived deep motions shows instability, which naturally leads to the genesis and maintenance of a large, isolated vortex similar to the GRS.

Thesis Files