The effects of evolving ice crystal aspect ratio during riming

We have built an ice growth parameterization where axis lengths evolve due to both temperature dependent vapor depositional growth and riming. We use a single particle growth model to compare our growth evolution and fall speed to wind tunnel data. These results show our model can successfully capture the effects of light riming on mass growth and fall speed. We also can capture the transitional growth of ice crystals to graupel. This transitional growth is missing from most traditional microphysical models that rely on autoconversion between snow and graupel categories. We are also developing a bulk version for use in the Weather Research and Forecasting (WRF) model. Initial tests of this parameterization involve using bulk vapor growth and binned riming in a two-dimensional kinematic model. We use a convective flow field and show the resulting precipitation from our model differs from traditional models partly due to using transitional riming growth instead of autoconversion.