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

严重的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和数百人的伤亡。冰雹、冻雨、极端降雨以及与之相关的夏季洪水和山体滑坡、冬季的雷暴和冰暴是本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，对这种对流云和降水系统的形式、强度和错位进行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，由于对混合相云和降水粒子的微观物理了解甚少而受到影响。特别是，需要适当地表示雪、冰雹和冰雹的融化过程。HELCOMET项目的目的是提供一套描述融化冰水流星最重要物理性质的参数，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分数。此外，还将研究气流中的湍流以及融化的水流星与过冷液滴的碰撞。实验将在美因茨垂直风洞进行，这是世界上唯一的在模拟大气条件下研究单一云和降水粒子的设施。将在降水模式和雷达反演算法中实施由HELCOMET实验提供的融化冰水流星微观物理性质的新的参数化。

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.