PyCHAM: CHemistry with Aerosol Microphysics in Python

Abstract

PyCHAM (CHemistry with Aerosol Microphysics in Python) is an open-access 0-D box model for aerosol chamber studies. Aerosol chambers provide a means for atmospheric scientists to interrogate aerosol processes (Finlayson-Pitts & Pitts, 2000; Hidy, 2019; Schwantes et al., 2017). Allying PyCHAM with chamber measurements allows quantification of unknown parameters, such as branching ratios for oxidation schemes (Chen & Griffin, 2005). Although several box models have already been published (Pierce et al., 2008; Roldin et al., 2019, 2014; Sunol, Charan, & Seinfeld, 2018), PyCHAM is novel in its ease of accessibility and utility. To the best of our knowledge, PyBOX (Topping, Connolly, & Reid, 2018), which formed the basis of PyCHAM, and AtChem (Borońska et al., 2019), are the only other open source box models with graphical user interfaces. However, PyCHAM provides a considerable upgrade to the functionality of both prior models, as AtChem only simulates gas-phase photochemistry and PyBOX has limited particle effects, whilst PyCHAM models significantly more particle microphysics (detailed below) and wall effects, in addition to gas-phase photochemistry. The intention therefore, is that it will be readily employed by research groups undertaking aerosol chamber measurements.