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The THOR + HELIOS general circulation model: multiwavelength radiative transfer with accurate scattering by clouds/hazes

2022; Oxford University Press; Volume: 512; Issue: 3 Linguagem: Inglês

10.1093/mnras/stac680

1365-2966

Russell Deitrick, Kevin Heng, U. Schroffenegger, Daniel Kitzmann, Simon L. Grimm, Matej Malik, João M. Mendonça, Brett M. Morris,

Stellar, planetary, and galactic studies

ABSTRACT General circulation models (GCMs) provide context for interpreting multiwavelength, multiphase data of the atmospheres of tidally locked exoplanets. In the current study, the non-hydrostatic THOR GCM is coupled with the HELIOS radiative transfer solver for the first time, supported by an equilibrium chemistry solver (FastChem), opacity calculator (HELIOS-K), and Mie scattering code (LX-MIE). To accurately treat the scattering of radiation by medium-sized to large aerosols/condensates, improved two-stream radiative transfer is implemented within a GCM for the first time. Multiple scattering is implemented using a Thomas algorithm formulation of the two-stream flux solutions, which decreases the computational time by about 2 orders of magnitude compared to the iterative method used in past versions of HELIOS. As a case study, we present four GCMs of the hot Jupiter WASP-43b, where we compare the temperature, velocity, entropy, and streamfunction, as well as the synthetic spectra and phase curves, of runs using regular versus improved two-stream radiative transfer and isothermal versus non-isothermal layers. While the global climate is qualitatively robust, the synthetic spectra and phase curves are sensitive to these details. A THOR + HELIOS WASP-43b GCM (horizontal resolution of about 4 deg on the sphere and with 40 radial points) with multiwavelength radiative transfer (30 k-table bins) running for 3000 Earth days (864 000 time-steps) takes about 19–26 d to complete depending on the type of GPU.