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会给我们的社会带来很大的不便。这些可能是从主要的停电到空中和地面运输的中断。通常观测到的降水类型有冻雨、冰球和湿雪。它们的形成机制很复杂，因为它们与0°C左右的温度有关，这意味着温度的微小变化可以显著影响风暴的严重程度。本项目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（如雪的部分融化和再冻结）形成相关的微物理过程将在与完整大气模式耦合的微物理方案中实现。其次，研究不同降水类型对冬季风暴气象条件的影响。这意味着从相位变化、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导的中尺度环流。第三，研究与云和降水形成相关的微物理过程对高分辨率长期天气预报的敏感性。目前，天气预报模型在预测降水方面存在一定的局限性。随着计算机能力的提高，小尺度气象过程的分辨率变得越来越重要。综上所述，本研究项目将有助于更好地了解不同类型冬季降水在预测短期和长期极端冬季天气事件中的作用。

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.