Impacts of precipitation type formation on the dynamics and thermodynamics of winter storms

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The different types of precipitation associated with winter storms can cause major inconveniences for our societies. These can be from major power outages to disruption of air and ground transportation. The different types of precipitation commonly observed are on the form of freezing rain, ice pellets and wet snow. Their formation mechanisms are complex because they are associated with temperatures around 0°C meaning that only a small change in temperature can affect dramatically the severity of the storm. This research program aims to better understand their formation mechanisms and the impact on the mesoscale circulation induced by phase changes. Numerical modelling is the key tool to achieve our goal. First, the microphysical processes associated with the formation of different types of precipitation such as partial melting and refreezing of snow will be implemented in a microphysics scheme coupled to a complete atmospheric model. Second, the impact of different types of precipitation on the meteorological conditions of winter storms will be studied. This implies the study of induced mesoscale circulation from phase changes, the distribution of types and rates of precipitation as well as changes in temperature, moisture and wind speed. Third, the sensitivity of the microphysical processes associated with the cloud and precipitation formation on high-resolution long-term weather predictions will be studied. Currently, the weather prediction models are limited in terms of predicting precipitation. The resolution of small-scale meteorological processes is becoming increasingly important with the increasing power of computers. In summary, this research program will contribute to a better understanding of the role of different types of winter precipitation on predicting short-and long-term extreme winter weather events.