  The atmospheres of ultra hot Jupiters (UHJs) are prime targets for the
detection of molecules and atoms at both low and high spectral resolution. We
study the atmospheres of the UHJs WASP-121b and WASP-189b by performing 3D
general circulation models (GCMs) of these planets using high temperature
correlated-k opacity schemes with ultra-violet (UV) absorbing species included.
The GCM results are then post-processed at low and high spectral resolutions
and compared to available data. The high resolution results are
cross-correlated with molecular and atomic templates to produce mock molecular
detections. Our GCM models produce similar temperature-pressure (T-p) structure
trends to previous 1D radiative-convective equilibrium models of UHJs.
Furthermore, the inclusion of UV opacities greatly shapes the thermal and
dynamical properties of the high-altitude, low-pressure regions of the UHJ
atmospheres, with sharp T-p inversions due to the absorption of UV light. This
suggests that optical wavelength, high-resolution observations probe a
dynamically distinct upper atmospheric region, rather than the deeper jet
forming layers.
