  We present a 3D general circulation model of Pluto and Triton's atmospheres,
which uses radiative-conductive-convective forcing. In both the Pluto and
Triton models, an easterly (prograde) jet is present at the equator with a
maximum magnitude of 10-12 m/s and 4 m/s, respectively. Neither atmosphere
shows any significant overturning circulation in the meridional and vertical
directions. Rather, it is horizontal motions (mean circulation and transient
waves) that transport heat meridionally at a magnitude of 1 and 3 x 10^7 W at
Pluto's autumn equinox and winter solstice, respectively (seasons referenced to
the Northern Hemisphere). The meridional and dayside-nightside temperature
contrast is small (<5 K). We find that the lack of vertical motion can be
explained on Pluto by the strong temperature inversion in the lower atmosphere.
The height of the Voyager 2 plumes on Triton can be explained by the dynamical
properties of the lower atmosphere alone (i.e., strong wind shear) and does not
require a thermally defined troposphere (i.e., temperature decreasing with
height at the surface underlying a region of temperature increasing with
height). The model results are compared with Pluto stellar occultation light
curve data from 1988, 2002, 2006, and 2007 and Triton light curve data from
1997.
