**Randomly Forced, 2-D Planetary Turbulence of the Jovian Atmosphere**

**J. Y-K. Cho, A. P. Ingersoll (Caltech), L. M. Polvani (Columbia)**

Recently, it has been demonstrated that the banded appearance and
the zonal winds in the atmospheres of the giant planets can be
well-modeled by idealizing the atmosphere as a shallow layer of
turbulent fluid [Cho & Polvani, *Science* (1996)]. In that
work, robust and steady jets form from random initial conditions
and no forcing, in good qualitative agreement with the observed
winds on all four of the giant planets.

In this work, we re-address the problem of jet morphology with a
simple extension of the above model: random forcing with variable
scale and correlation time. Such forcing can serve as a simple model
of convection or baroclinic instability. Our objective here is to
determine clearly the role of this forcing, which is independent
of the flow, on the jet structures. To this end, we reduce the
model to the non-divergent barotropic vorticity equation in
spherical geometry. Similar systems were previously studied
[see Rhines, *Chaos* (1994) and Cho & Polvani, *Phys.
Fluids* (1996), and references therein]. Here, we extend the
previous works by performing long-time simulations in full spherical
geometry with a much broader exploration of the parameter space.

In our study, we find no region of parameter space that produces steady, robust jets as in the observations. Furthermore, when the forcing is not spatially symmetric, the banding becomes weak. These results strongly indicate that the simple random forcing used here and in many earlier works overwhelms the flow, and a more physical forcing, one that is affected in turn by the generated flow, is needed.