HAPI2LIBIS (v1.0): a new tool for flexible high-resolution radiative transfer computations with libRadtran (version 2.0.5)

Abstract. Atmospheric radiative transfer (RT) models are useful tools to increase our understanding of the physical interactions and processes occurring in the atmosphere and surface. In the category of free and open-source models, the library for radiative transfer (libRadtran) is a widely used and versatile package. However, running high-resolution calculations with libRadtran is often tedious since libRadtran does not include all the required information to run line-by-line executions (i.e., resolving individual spectral lines of gases) in a flexible way under specific atmospheric conditions, meaning that external software is required. This poses a problem for a user since generating necessary files for libRadtran requires familiarity with the topic of molecular spectroscopy in addition to knowing how to use the external software, which may not be tailored for producing libRadtran-compatible files. In this paper, we present HAPI2LIBIS, a compact software tool intended to be used in close connection with libRadtran to enable easy high-resolution calculations. HAPI2LIBIS streamlines the generation of high-resolution molecular absorption data for libRadtran by utilizing the latest version of the High-Resolution Transmission Molecular Absorption (HITRAN) database and the HITRAN Application Programming Interface (HAPI) with user-specified spectral ranges and atmospheric profiles. HAPI2LIBIS also stores computed absorption cross-sections in its dynamically constructed lookup table and includes an option for pressure- and temperature-dependent interpolation in order to accelerate subsequent simulations.