# A reduced chemical scheme for modelling warm to hot hydrogen-dominated atmospheres

## TL;DR

This paper introduces a simplified chemical scheme with 30 species for 3D atmospheric modeling of warm to hot hydrogen-rich planets and brown dwarfs, enabling faster computations without significant accuracy loss.

## Contribution

A new reduced chemical scheme for 3D atmospheric modeling that balances computational efficiency and accuracy for a wide range of warm planetary atmospheres.

## Key findings

- Accurately reproduces vertical profiles of key observable species.
- Valid for a broad temperature range, excluding hot C-rich atmospheres.
- Applicable in both 1D and 3D models for exoplanets and brown dwarfs.

## Abstract

Three dimensional models that account for chemistry are useful tools to predict the chemical composition of (exo)planet and brown dwarf atmospheres and interpret observations of future telescopes. Recent Juno observations of the NH3 tropospheric distribution in Jupiter also indicate that 3D chemical modelling may be necessary to constrain the deep composition of the giant planets of the Solar System. However, due to the high computational cost of chemistry calculations, 3D chemical modelling has so far been limited. A solution to include chemical kinetics in a 3D model is to use a reduced chemical scheme. In this view, we have developed a reduced scheme containing 30 species and 181 reversible reactions, from the full chemical scheme of Venot et al. 2012. This scheme reproduces accurately the vertical profiles of the observable species (H2O, CH4, CO, CO2, NH3, and HCN) and has a large range of validity. It can be used to study all kind of warm atmospheres, except hot C-rich ones, which contains a high amount of C2H2. It can be used in 1D models, for fast computations, but also in 3D models for hot giant (exo)planet and brown dwarf atmospheres.