Jovian Planetary Waves
J. Harrington (NRC/NASA GSFC), D. Deming (NASA GSFC)
We have found over two dozen discrete, linearly-propagating, periodic features in 5-m m images of Jovian cloud opacities (J. Harrington et al. 1996, Icarus 124, 32-44). Numerous spatially-sinusoidal temperature oscillations also appear in several passbands between 7 and 19 (D. Deming et al. 1997, Icarus 126, 301-312). Both types of Jovian planetary-scale features are zonally-oriented. They have always been detected when sought (1989, '91, '92, '93), and some individual features persist 100 Earth days or longer. These features are superficially consistent with Rossby waves, but they do not follow a simplistic dispersion relation based on cloud-top wind speeds. Planetary wavenumbers are never larger than 15, consistent with predictions based on the Rhines scale for Jupiter.
There are many outstanding phenomenological questions: Where and how are the waves driven? How are waves at different atmospheric levels related? What are their true dispersion properties? How long do they last? We are continuing observations and will conduct a search of the Hubble Space Telescope archive for the 1 meridional cloud-belt deviations expected for Rossby waves. We are in the process of correlating wave detections of various types, times, and wavelengths with each other. Our goal is to constrain atmospheric stratification and vertical energy transport. Because Rossby waves propagate vertically, these features may probe conditions at the interface between the meteorological atmosphere and the planetary interior.
Work supported by NASA Planetary Astronomy RTOP 196-41-54. Work performed while J. H. held a National Research Council - NASA Goddard Space Flight Center Research Associateship.