Abstract

Peter Read + Arrate Antunano, John Barbara, Simon Cabanes, Greg Colyer, Teresa del Río Gaztelurrutia, Agustin Sanchez-Lavega & Roland Young Recent analyses of wind measurements from tracking cloud motions in spacecraft images of Jupiter and Saturn indicate that scale to scale transfers of kinetic energy act from small to large scales over a wide range of length scales, much as anticipated for 2D or geostrophic turbulence paradigms. At the smallest resolvable scales, however, there is evidence of a forward (downscale) transfer, at least at low and middle latitudes on Jupiter. Moreover, the upscale transfers at the largest spatial scales are evidently dominated by direct, spectrally non-local eddy-zonal interactions, in contrast to more classical scenarios, associated with the generation of intense zonal jets, alternating in latitude, via the divergence or convergence of horizontal Reynolds stresses. Most analyses to date have emphasised the global mean interactions for both planets, thereby focusing on the spatially homogeneous components of the turbulence. But more recent observations indicate that the dynamics of these atmospheres varies significantly with latitude from the tropics to the polar regions. Here we present some new analyses of spectral energy transfers on both Jupiter and Saturn that resolve variations in latitude. The (preliminary) results indicate significant variability between different locations, with a clear distinction between the tropics, the extratropical middle latitudes and the polar regions. We discuss these in light of other observations and models of gas giant circulation.