Examining NHD versus QHD in the GCM THOR with non-grey radiative transfer for the hot Jupiter regime

Global circulation models (GCMs) play an important role in contemporary investigations of exoplanet atmospheres. Different GCMs evolve various sets of dynamical equations, which can result in obtaining different atmospheric properties between models. In this study, we investigate the effect of different dynamical equation sets on the atmospheres of hot Jupiter exoplanets. We compare GCM simulations using the quasi-primitive dynamical equations (QHD) and the deep Navier-Stokes equations (NHD) in the GCM THOR. We utilize a two-stream non-grey 'picket-fence' scheme to increase the realism of the radiative transfer calculations. We perform GCM simulations covering a wide parameter range grid of system parameters in the population of exoplanets. Our results show significant differences between simulations with the NHD and QHD equation sets at lower gravity, higher rotation rates, or at higher irradiation temperatures. The chosen parameter range shows the relevance of choosing dynamical equation sets dependent on system and planetary properties. Our results show the climate states of hot Jupiters seem to be very diverse, where exceptions to prograde superrotation can often occur. Overall, our study shows the evolution of different climate states that arise just due to different selections of Navier-Stokes equations and approximations. We show the divergent behaviour of approximations used in GCMs for Earth but applied for non Earth-like planets.

Automated summary

This study compares simulations of the atmospheres of hot Jupiter exoplanets using different dynamical equation sets in global circulation models (GCMs). The results show significant differences between simulations with different equation sets under certain conditions. The study highlights the importance of selecting the appropriate equation set based on system and planetary properties and shows the divergent behavior of approximations used in GCMs for non Earth-like planets.