Microphysical structure of convective snow clouds simulated by an improved version of multi-dimensional bin model

A new version of bin-microphysics model, which uses four dimensions to represent ice-particle properties (ice mass, solute mass, aspect ratio and apparent volume) and two dimensions for liquid-drop properties (water mass and solute mass), is developed to simulate microphysical structure of clouds. As tests, the model is incorporated into an adiabatic parcel model and an idealized one-dimensional model to simulate the developing and mature stages of a convective snow cloud observed over the Sea of Japan. The water content and the size distribution of super-cooled drops, and the prevailing type of ice crystals are well consistent with the observations. The model also reveals that crystals originating from deposition/ condensation-freezing nuclei grow most quickly in the convective snow cloud, and isometric crystals among them would act as embryos of graupels in later stage.