Abstract
Abstract THOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or solar-system-centric tunings. It solves the general nonhydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building on the work of Mendonça et al. First, while the horizontally explicit and vertically implicit integration scheme is the same as that described in Mendonça et al., we provide a clearer description of the scheme and improve its implementation in the code. The differences in implementation between the hydrostatic shallow, quasi-hydrostatic deep, and nonhydrostatic deep treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and nonhydrostatic simulations are negligible in the Earth case but pronounced in the hot Jupiter case. Finally, the effects of the so-called “sponge layer,” a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR.
Highlights
While that study compared simulations using the primitive equations with the full nonhydrostatic equations, the sole difference between our simulations here is the neglect of the material derivative of the vertical velocity, Dvr/Dt, and the hyperdiffusive term, vr, in the QHD case
We have presented a suite of simulations using the dynamical core (THOR)
We have reproduced the general features of several benchmarks for dynamical cores: a synchronously rotating Earth, a deep hot Jupiter, and wave tests previously presented in Tomita & Satoh (2004)
Summary
With new technology and data analysis techniques, we are entering an era in which 3D models of exoplanet atmospheres can be tested and validated. Numerous theoretical and computational studies have shown that hot Jupiters have large day/night temperature contrasts and equatorial superrotation (Showman & Guillot 2002; Cooper & Showman 2005; Dobbs-Dixon & Lin 2008; Showman et al 2009; Dobbs-Dixon et al 2010; Rauscher & Menou 2010, 2012; Heng et al 2011a, 2011b; Dobbs-Dixon & Agol 2013; Perez-Becker & Showman 2013; Kataria et al 2015; Amundsen et al 2016) These features are broadly consistent across a wide range of models and have been validated by observations (Snellen et al 2010; Knutson et al 2012; Louden & Wheatley 2015). The goals of this paper are to consolidate descriptions of improvements that have been made to the model since Mendonça et al (2016), clarify the model framework, validate the new physics, and compare results from the model using different approximations, with implications for the general circulation of hot Jupiters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
