Interaction between eddies and mean flow in Jupiter's atmosphere: Analysis of Cassini imaging data

Beebe et al. [Beebe, R.F., et al., 1980. Geophys. Res. Lett. 17, 1-4] and Ingersoll et al. [Ingersoll, A.P., et al., 1981. J. Geophys. Res. 86, 8733-8743] used images from Voyagers 1 and 2 to analyze the interaction between zonal winds and eddies in Jupiter's atmosphere. They reported high positive correlation between Jupiter's eddy momentum flux, p (u ' v ') over bar, and the variation of zonal velocity with latitude, d (u) over bar /dy. This correlation a value more than 10% of Jupiter's thermal implied a surprisingly high rate of conversion of energy from eddies to zonal flow: similar to 1.5-3.0 W m(-2), flux emission. However, Sromovsky et al. [Sromovsky, L.A., et al., 1982. J. Atmos. Sci. 39, 1413-1432] argued that possible biases in the analysis could have caused an artificially high correlation. In addition, significant differences in the derived eddy flux between datasets put into question the robustness of any one result. We return to this long-standing puzzle using images of Jupiter from the Cassini flyby of December 2000. Our method is similar to previous analyses, but utilizes an automatic feature tracker instead of the human eye. The number of velocity vectors used in this analysis is over 200,000, compared to the 14,000 vectors used by Ingersoll et al. We also find a positive correlation between (u ' v ') over bar and d (u) over bar /dy and derive a global average power per unit mass, (u ' v ') over bar d (u) over bar /dy, ranging from (7.1-12.3) x 10(-5) W ka(-1). Utilizing Ingersoll et al.'s estimate of the mass per unit area involved in the transport, this would imply a rate of energy conversion of similar to 0.7-1.2 W m(-2). We discuss the implications of this result and employ several tests to demonstrate its robustness. (c) 2006 Elsevier Inc. All rights reserved.