  Observations of brown dwarfs (BDs), free-floating planetary-mass objects, and
directly imaged extrasolar giant planets (EGPs) exhibit rich evidence of
large-scale weather. Cloud radiative feedback has been proposed as a potential
mechanism driving the vigorous atmospheric circulation on BDs and directly
imaged EGPs, and yet it has not been demonstrated in three-dimensional
dynamical models at relevant conditions. Here we present a series of
atmospheric circulation models that self-consistently coupled dynamics with
idealized cloud formation and its radiative effects. We demonstrate that
vigorous atmospheric circulation can be triggered and self-maintained by cloud
radiative feedback. Typical isobaric temperature variation could reach over 100
K and horizontally averaged wind speed could be several hundred m/s. The
circulation is dominated by cloud-forming and clear-sky vortices that evolve
over timescales from several to tens of hours. The typical horizontal
lengthscale of dominant vortices is closed to the Rossby deformation radius,
showing a linear dependence on the inverse of rotation rate. Stronger rotation
tends to weaken the vertical transport of vapor and clouds, leading to overall
thinner clouds. Domain-mean outgoing radiative flux exhibits variability over
timescales of tens of hours due to the statistical evolution of storms.
Different bottom boundary conditions in the models could lead to qualitatively
different circulation near the observable layer. The circulation driven by
cloud radiative feedback represents a robust mechanism generating significant
surface inhomogeneity as well as irregular flux time variability. Our results
have important implications for near-IR colors of dusty BDs and EGPs, including
the scatter in the near-IR color-magnitude diagram and the viewing-geometry
dependent near-IR colors.
