In this work we present a report on the GASS microphysics project and the International Cloud Modelling Workshop projects, i.e. the Kinematic Driver – Aerosol (KiD-A) project. This project was motivated by the aforementioned differences between closed and open cell within stratocumulus and the specific aim of this project is to better understand in-cloud aerosol processing as well as investigate how aerosol processing depends on the numerical techniques. In order to achieve this aim, KiD-A uses a publicly available kinematic framework to compare langrangian microphysics schemes, spectral bin microphsyics schemes and bulk microphysics schemes. This is the first time such an intercomparison has taken place. The preliminary results indicated generally good agreement between all models in the absence of sedimentation and collision-coalescence. However, when all processes occur, the models vary substantially, with the more detailed models exhibiting a much larger range in cloud characteristics (e.g., liquid water path) than that of the simpler models. Subsequent work has been performed to elucidate the cause of the large model spread by closely examining the drop size distributions predicted by the different models as well as the representation of collection and sedimentation in the models. In this presentation these new results will be discussed.