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

与冬季风暴相关的不同类型的降水可能会给我们的社会带来重大不便。这些可能是从重大停电到空中和地面交通中断。常见的降水类型有冻雨、冰球和湿雪。它们的形成机制很复杂，因为它们与0摄氏度左右的温度有关，这意味着只有温度的微小变化才能显著影响风暴的严重程度。这项研究计划旨在更好地了解它们的形成机制以及相变对中尺度环流的影响。数值模拟是实现我们目标的关键工具。首先，与不同类型降水的形成有关的微物理过程，如雪的部分融化和重新冻结，将在一个与完整的大气模型相耦合的微物理方案中实施。二是研究不同类型降水对冬季风暴气象条件的影响。这意味着从相变、降水类型和速率的分布以及温度、湿度和风速的变化来研究诱发的中尺度环流。第三，将研究与云和降水形成有关的微物理过程对高分辨率长期天气预报的敏感性。目前，天气预报模式在预报降水方面存在局限性。随着计算机能力的增强，小规模气象过程的分辨率变得越来越重要。总而言之，这项研究计划将有助于更好地了解不同类型的冬季降水在预测短期和长期极端冬季天气事件方面的作用。

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.