EOS: Atmospheric Radiative Transfer in Habitable Worlds with HELIOS

Matej Malik,Michele Maris,Laura Silva,Stavro L. Ivanovski,Giovanni Vladilo,Paolo Simonetti,Jost von Hardenberg,Lorenzo Biasiotti

doi:10.3847/1538-4357/ac32ca

Abstract

Abstract We present EOS, a procedure for determining the outgoing longwave radiation (OLR) and top-of-atmosphere (TOA) albedo for a wide range of conditions expected to be present in the atmospheres of rocky planets with temperate conditions. EOS is based on HELIOS and HELIOS-K, which are novel and publicly available atmospheric radiative transfer (RT) codes optimized for fast calculations with GPU processors. These codes were originally developed for the study of giant planets. In this paper we present an adaptation for applications to terrestrial-type, habitable planets, adding specific physical recipes for the gas opacity and vertical structure of the atmosphere. To test the reliability of the procedure, we assessed the impact of changing line opacity profile, continuum opacity model, atmospheric lapse rate, and tropopause position prescriptions on the OLR and the TOA albedo. The results obtained with EOS are in line with those of other RT codes running on traditional CPU processors, while being at least one order of magnitude faster. The adoption of OLR and TOA albedo data generated with EOS in a zonal and seasonal climate model correctly reproduces the fluxes of the present-day Earth measured by the CERES spacecraft. The results of this study disclose the possibility to incorporate fast RT calculations in climate models aimed at characterizing the atmospheres of habitable exoplanets.

Highlights

IntroductionMany different climate models have been published
Planetary climate simulations are fundamental tools in the search for Earth-like habitable worlds outside the Solar System because, with a proper parameterization of physical quantities, they allow us to estimate the physical conditions in the deeper atmospheric layers and on planetary surfaces from the limited amount of observational data which are typically available for exoplanets.During the years, many different climate models have been published
EOS is based on HELIOS and HELIOS-K, which are novel and publicly available atmospheric radiative transfer (RT) codes optimized for fast calculations with graphical processing units (GPUs) processors

Summary

Introduction

Many different climate models have been published They can be categorized either as intermediate/high complexity General Circulation Models (GCMs) or as low complexity Energy Balance Models (EBMs). GCMs perform 3-D hydrodynamical calculations of the atmosphere, taking into account the surface geography and tracking a large number of interactions between different components of the climate system (Lin & Rood 1996; Hourdin et al 2006). They allow for state-of-the-art predictions but require a large number of input parameters that are usually not known for exoplanets and are very computationally intensive. EBMs require a relatively small number of input parameters and far less computational resources, which in turn allow for their use in the rapid exploration of the broad parameters space that characterizes exoplanets (Silva et al 2017; Murante et al 2020)

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