Atmospheric Radiative Transfer Generalised for Use on Earth and Other Planets: ARTS 2.2

One of the major differences in radiative-transfer modeling in the atmospheres of Earth and other planets arises from the different composition of the atmospheres. When interested in measuring total abundance or even vertical distribution of atmospheric constituents, knowledge of parameters describing spectrally dependent absorption in dependence of atmospheric state is required. When modeling radiative transfer for different planets, the line shapes are often accounted for by scaling the parameters valid for Earth’s “air” or by building a spectroscopic catalogue specific to the planet in question and its main atmospheric composition. This strongly limits applicability of these models. Based on the ARTS model (www.sat.ltu.se/arts), we have developed a toolbox for microwave atmospheric radiative transfer in solar system planets. As part of this, we developed and implemented a more generalized absorption calculation approach that is able to flexibly handle largely different atmospheric compositions. In order to facilitate this approach, we compiled a spectroscopic catalogue for the 0-3 THz spectral range that reports broadening and shift parameters for individual molecular species. Currently it covers the most abundant species in Earth and its neighboring planets (Venus, Mars, Jupiter). All spectroscopic data has been collected from literature (when available) or adapted from the HITRAN, GEISA, or JPL catalogues. Here, we present the generalized approach, introduce the spectroscopic catalogue in more depth, and show example results of absorption calculations for different planets underlining the relevance of our approach. Based on this experience, we recommend the reporting of broadening/shift parameters of individual species in spectroscopic catalogues like HITRAN in the future.