Wind tunnel studies on the melting of ice hydrometeors: the effect of collision and turbulence on melting (HydroCOMET)

强降水事件每年在欧洲和世界范围内造成数十亿欧元的经济损失，并造成数百人受伤和死亡。冰雹、冻雨、极端降雨以及夏季雷暴和冬季冰暴造成的洪水和山体滑坡是我们大陆最危险的天气现象，具有有害的经济、社会和自然影响。因此，对这类对流云和降水系统的形态、强度和位置的短期预报是至关重要的。用于短期天气预报的工具，即数值天气模式和基于雷达的遥感降水设施，受到对混合相云和降水粒子的微物理学知之甚少的影响。特别是，雪，冰雹和霰的融化过程的适当表示是必需的。HydroCOMET项目的目的是提供一套参数化，描述融冰水凝物最重要的物理特性，包括它们不断变化的形状、下落速度和融化过程中的液态水比例。此外，还将研究气流中湍流的影响以及熔融水凝物与过冷液滴的碰撞。实验将在美因茨垂直风洞进行，这是一个世界范围内独一无二的设施，用于研究模拟大气条件下的单云和降水粒子。水文气象学实验提供的融冰水凝物微物理特性的新参数化将在降水模型和雷达反演算法中实施。

Severe precipitation events are responsible for billions of Euros economic loss and cause hundreds of injuries and fatalities every year in Europe and worldwide. Hail, freezing rain, extreme rainfall and the associated floods and landslides from summer time thunderstorms and ice storms in winter are the most hazardous weather phenomena in our continent having harmful economic, societal and natural impacts. Therefore, the short term forecast of the form, intensity and dislocation of such convective cloud and precipitation systems is of crucial importance. The tools used for short term weather prediction, i.e. the numerical weather models and the radar based remote sensing precipitation facilities suffer from the poorly understood microphysics of the mixed phase cloud and precipitation particles. In particular, proper representation of the melting processes of snow, hail and graupel is required. The aim of the HydroCOMET project is to deliver a set of parameterizations describing the most important physical properties of melting ice hydrometeors, including their continuously varying shape, fall velocities, and their liquid water fraction during melting. Furthermore, the effects of turbulence in the air stream and the collision of melting hydrometeors with supercooled droplets will be investigated. The experiments will be carried out at the Mainz vertical wind tunnel which is a world-wide unique facility for investigating single cloud and precipitation particles under simulated atmospheric conditions. New parameterizations of the microphysical properties of melting ice hydrometeors provided by the HydroCOMET experiments will be implemented in precipitation models and radar retrieval algorithms.