The MESSy chamber DWARF: a box model for simulating chamber experiments (based on MESSy v2.55.2)

Abstract. Numerical simulation of environmental chamber experiments is essential for improving models of atmospheric composition. This task often relies on box models, which are not integral to three-dimensional atmospheric chemical transport models. Here, we present an application of the Modular Earth Submodel System (MESSy) DWARF model for chamber simulation experiments. It was developed as a zero-dimensional chemical box model of atmospheric oxidation. Chamber-specific features—including the injection of trace gases, variable radiation conditions, gas- and aqueous-phase chemistry, wall emissions, and dilution—are represented using existing and adapted MESSy submodels. We describe the multi-phase kinetic framework, the estimation of aerosol liquid water content and a simplified treatment of wall losses. We tested the MESSy chamber DWARF setup with experiments from three environmental chambers: The SAPHIR and SAPHIR-STAR chambers at Forschungszentrum Jülich, and the BATCH chamber at the University of Bayreuth. These chambers cover diverse designs and experimental conditions. The model reproduces observed time series of radicals, nitrogen oxides and ozone during an experiment in SAPHIR in which 2-methyl-3-butene-2-ol was oxidised. In another test the model was used to check the consistency of the experimental boundary conditions in the BATCH chamber. Further chamber DWARF tests also show that the framework can predict organic aerosol mass concentration via kinetic partitioning between the gas phase and deliquescent particles in SAPHIR-STAR. Modeled organic mass concentration during this experiment where α-pinene was oxidised agrees well with observations, supporting the framework’s ability to simulate the chemical evolution in both the gaseous and aqueous phase. The MESSy chamber DWARF provides a useful tool for developing and evaluating kinetic models. Within this framework, we can test new laboratory findings directly for their atmospheric relevance. Thanks to the MESSy framework, we can use the same kinetic model for global simulations.