Extension of the cloud modeling capabilities of Transit and future applications

The presence of aerosols can dramatically alter the spectrum of a planetary atmosphere either in transmission or emission. It is therefore important for atmospheric parameter retrieval codes to offer a selection of parameterized wavelength-dependent cloud models. Here, we present our additions to the cloud modeling capabilities of Transit, the radiative-transfer code in the Bayesian Atmospheric Radiative Transfer retrieval package: (Cubillos et al. 2016), (Blecic et al. 2016), (Harrington et al. 2016). We implement the four cases of Barstow (2020); Barstow et al. (2017), Tsiaras et al. (2018), Pinhas et al. (2019) and Fisher & Heng (2018). The model outlined in Barstow et al. (2017) features a cloud with variable pressure levels and extinction efficiency proportional to the wavelength raised to the scattering index. Pinhas et al. (2019) employs a similar model with the addition of an opaque grey cloud underneath. Both Fisher & Heng (2018) and Tsiaras et al. (2017) use effectively the same model. An analytical model to capture the functional dependence of cloud extinction on wavelength. However, the latter supports an opaque grey cloud and fixed parameters. These four options will stand to triple the number of cloud models available in BART and increase its flexibility in retrieval. This research was supported by NASA Exoplanets Research Program grant NNX17AB62G.