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EOS: flexible radiative transfer for rocky exoplanets climate simulations

Presentation #102.299 in the session Poster Session.

Published onJun 20, 2022
EOS: flexible radiative transfer for rocky exoplanets climate simulations

Climate models are fundamental tools to assess the physical conditions in the deep atmosphere or on the surface of exoplanets from the scant available data. Moreover, they allow the community to single out the most interesting targets for future observations. A core component is the vertical radiative transfer (RT) module, which takes care of calculating the outgoing longwave radiation (OLR) and top-of-atmosphere (TOA) albedo for a set of input parameters such as the atmospheric composition and temperature-pressure structure, the instellation spectrum and so on.

Here we present EOS, a new RT procedure for rocky exoplanets of astrobiological interest (Simonetti et al. 2022). This procedure is based on the RT model HELIOS (Malik et al. 2017, 2019) and the opacity calculator HELIOS-K (Grimm & Heng 2015, Grimm et al. 2021), which are publicly available, fast GPU-based codes developed for the study of Jupiter-like planets. As part of our effort, we updated them with state-of-the-art prescriptions tailored for habitability studies. In particular we: (i) added the treatment for the continuum absorption features of H2O (Clough et al. 1989, Mlawer et al. 2012) and CO2 (Gruszka & Borysow 1998, Baranov et al. 2004, Baranov 2018), (ii) expanded the treatment of the sub-Lorentzian line wing profile of CO2 (Perrin & Hartmann 1989, Tonkov et al. 1996) and (iii) considered the effects of non-ideal behaviour of CO2 and H2O on lapse rate in high-pressure, near-condensation conditions (Kasting 1988, 1991). We then tested the numerical robustness of EOS against changes in model variables and performed a comparison with other codes employed in this field of study. We stress that EOS can be applied to a diversity of cases that usually require a variety of custom-built codes.

The results of EOS can be used to fit polynomial relations or to compile lookup tables for OLR and TOA albedo that can then be used in a variety of 2D (like HEXTOR, see Haqq-Misra et al. 2022) and 3D climate simulations. We used it to upgrade the RT treatment of ESTM, an energy balance model with enhanced prescriptions for meridional and vertical transport and surface ice formation (Vladilo et al. 2013, 2015, Biasiotti et al. submitted). The flexibility and efficiency of ESTM coupled with EOS allow for the rapid exploration of the atmospheric and planetary parameter space, calculating quantitative indices of habitability to map circumstellar and circumbinary habitable zones with a higher degree of precision than single-column models.

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