ERF-SDM Simulations of a Convection Cloud Chamber: Model Development, Benchmark Evaluation, and Aerosol-Cloud-Turbulence Interactions

Abstract. Convection cloud chambers provide a unique platform for investigating aerosol cloud turbulence interactions under well controlled laboratory conditions and for evaluating numerical cloud microphysics models. This study extends the Energy Research and Forecasting model coupled with the Super Droplet Method (ERF-SDM) to simulate statistically stationary cloud chamber experiments through the implementation of Monin Obukhov similarity theory on all chamber walls, continuous aerosol injection, and wall deposition of super droplets. The model is evaluated using the recent Pi Chamber benchmark configuration from the cloud chamber modeling community and laboratory measurements from the Michigan Technological University Pi Chamber. ERF-SDM successfully represents characteristic chamber circulation and qualitative aerosol-dependent microphysical responses under the prescribed boundary conditions. Process-oriented analyses show that increasing aerosol injection strongly reduces mean and root-mean-square supersaturation, with most of the adjustment occurring between injection rates of 1 and 50 cm⁻³ min⁻¹. Higher injection rates also produce smaller cloud droplets and narrower droplet size distributions. However, the spatial standard deviation of supersaturation does not decrease monotonically, indicating that regulation of the mean thermodynamic state is not accompanied by a corresponding reduction in centered spatial variability. The simulations further demonstrate a transition from an aerosol limited regime at low aerosol injection rates to a vapor limited regime at higher aerosol loading, where competition for available water vapor increasingly limits aerosol activation. These results demonstrate that ERF-SDM, with the new cloud chamber capabilities, can effectively simulate laboratory cloud chamber experiments and investigate the coupled interactions among turbulence, supersaturation fluctuations, aerosol activation, and cloud microphysical evolution, providing valuable insights for understanding aerosol and cloud interactions in Earth system models.