General Circulation and Dynamical Transport of the Jovian Stratosphere
Zhang, X. (1), Showman, A. P. (1), and Yung Y. L. (2)
(1) Department of Planetary Sciences and Lunar and Planetary Laboratory, University of
Arizona, USA; (2) Division of Geological and Planetary Sciences, California Institute of
Technology, USA
Recent Cassini measurements during the Jupiter flyby in 2000 have greatly improved our
understanding of the Jovian stratosphere by revealing several key features: (1) large polar
heating due to solar-energy absorption by aggregated particles (Zhang et al., 2013a); (2)
inverse latitudinal trends between short-lived species (C2H2) and long-lived species
(C2H6) in the lower stratosphere (Zhang et al., 2013b); (3) decaying zonal (east-west) jet
structures with altitude in upper troposphere and lower stratosphere (Flaser et al., 2004,
Simon-Miller et al. 2006); (4) Temperature variations such as the Quasi-Quadrennial
Oscillation (QQO) in the lower stratosphere and pronounced wave-like structures in the
upper stratosphere (Zhang et al., 2013b; Greathouse et al., 2012). From those
observations we conclude that a large-scale Brewer-Dobson type meridional circulation
exists in the stratosphere of Jupiter and shapes the tracer transport, and that the
tropospheric waves propagate upward into the stratosphere and could play a significant
role in the eddy-mean flow interaction and vertical and horizontal mixing of the
temperature and tracer distributions. However, the detailed structure of the circulation
pattern and the underlying physical mechanisms of the stratospheric dynamical processes
remain unclear. In this presentation, we investigate this problem from three aspects in
order to elucidate the mechanism: (1) “Diagnostic approach”. We derive the stratospheric
residual mean circulation in the latitude and altitude plane, based on the observed diabatic
heating rate under the Transform Eulerian Mean framework (Andrew et al., 1987). A map
of horizontal eddy diffusivities is obtained from the relative potential vorticity gradient
and eddy potential vorticity flux, by assuming that large-scale, quasi-geostrophic eddies
are primarily responsible for the wave-mean flow interaction and horizontal tracer
transport; (2) “Tracer approach”. We introduce a two-dimensional photochemicaldiffusive-advective model to simulate the distribution of stratospheric hydrocarbons,
under the constraints of the latitudinal distributions of C2H2 and C2H6 (Zhang et al.,
2013b). From that the stratospheric advection and eddy mixing patterns responsible for
the tracer transport are derived. (3) “First Principles approach”. We construct a threedimensional stratospheric general circulation model (SGCM) of Jupiter adapted from the
MITgcm. Our simulations will investigate how the interactions between upward
propagating waves and the zonal-mean flow in the stratosphere lead to meridional
advection and diffusion. We will also investigate the mechanisms by which the waves
help to maintain the zonal-mean circulation; particular problems of interest include the
decay with height of the zonal jets in the lower stratosphere and the temperature
variations in the upper troposphere and lower stratosphere. This project was supported by
the Bisgrove Fellowship in the University of Arizona. YLY was supported by NASA
NNX09AB72G grant to the California Institute of Technology.