  We present a three dimensional hot Jupiter model, extending from 200 bar to 1
mbar, using the Intermediate General Circulation Model from the University of
Reading. Our horizontal spectral resolution is T31 (equivalent to a grid of
48x96), with 33 logarithmically spaced vertical levels. A simplified
(Newtonian) scheme is employed for the radiative forcing. We adopt a physical
set up nearly identical to the model of HD 209458b by Cooper & Showman
(2005,2006) to facilitate a direct model inter-comparison. Our results are
broadly consistent with theirs but significant differences also emerge. The
atmospheric flow is characterized by a super-rotating equatorial jet, transonic
wind speeds, and eastward advection of heat away from the dayside. We identify
a dynamically-induced temperature inversion ("stratosphere") on the planetary
dayside and find that temperatures at the planetary limb differ systematically
from local radiative equilibrium values, a potential source of bias for transit
spectroscopic interpretations. While our model atmosphere is quasi-identical to
that of Cooper & Showman (2005,2006) and we solve the same meteorological
equations, we use different algorithmic methods, spectral-implicit vs.
grid-explicit, which are known to yield fully consistent results in the Earth
modeling context. The model discrepancies identified here indicate that one or
both numerical methods do not faithfully capture all of the atmospheric
dynamics at work in the hot Jupiter context. We highlight the emergence of a
shock-like feature in our model, much like that reported recently by Showman et
al. (2009), and suggest that improved representations of energy conservation
may be needed in hot Jupiter atmospheric models, as emphasized by Goodman
(2009).

Earth and Planetary Astrophysics