Chempath 1.0: An open-source pathway analysis program for photochemical models

Abstract. We describe the development of Chempath: an open-source pathway analysis program for photochemical models. This algorithm can help understand the results of complex photochemical models by identifying the most important reaction chains (pathways) for the production and destruction of a species of interest in a reaction system. The algorithm can also quantify the contribution of the pathways to the production and destruction of a species.

We demonstrate how to apply Chempath to a one-dimensional photochemical model, using an example of a reaction system for Earth's present-day atmosphere. We validate that Chempath can identify well-known chemical mechanisms for O₃ production and destruction in this model, suggesting that this algorithm can be applied to understand photochemical models of less well-known atmospheres, like past and exoplanet atmospheres.