Towards a Bulk Approach of Local Interactions of Hydrometeors
Abstract. Growth of small cloud droplets and ice crystals is dominated by diffusion of water vapour. Usually, Maxwell's approach of growth for isolated particles is used in describing this process. However, recent investigations show that local interactions between particles can change diffusion properties of cloud particles. In this study we develop an approach for including these local interactions into a bulk model approach. For this purpose, a simplified framework of local interaction is proposed and governing equations are derived from this setup. The new model is tested against direct simulations and incorporated into a parcel model framework. Using the parcel model, possible implications of the new model approach on clouds are investigated. The results indicate that for specific scenarios the lifetime of cloud droplets in subsaturated air may be longer; these effects might have impact on mixed-phase clouds, e.g. in terms of riming efficiencies.