Observational and Theoretical Investigations Related to Hydrometeor Settling in Turbulent Air

数值天气和气候模式对冰冻降水下降速度的描述很敏感。许多模型仍然使用植根于近50年前的测量结果的计算方法。该奖项将提供有关降水下降速度的最新信息，包括湍流的影响。这项工作将使用一种名为机载粒子成像仪的新仪器来完成，该仪器旨在测量3D速度并对单个粒子进行高分辨率摄影。该奖项的主要更广泛的社会影响将是对数值模式所作假设的确认或改进，这可能会导致天气预报的改善。首席研究人员通过雪花图像提供了重要的公共宣传，新仪器应该会在这些图像的基础上进行改进。该工具还具有潜在的跨学科和技术转让用途。此外，该奖项还将提供教育和培训机会，包括对一名女退伍军人的支持。研究小组计划进行一个观察和理论项目，以提高对湍流大气如何影响降水下降速度的理解。该项目的一个核心方面将是开发机载粒子成像仪(AIP)，这是目前多角度雪花相机(MASC)的更新。AIP将最大限度地减少环境气流干扰，并在MASC现有能力的基础上增加3D速度测量。AIP将在2019-2020年冬季与其他仪器一起部署在复杂的水流星空中运动和图像捕获实验(圣杯)中，以将粒子类型、方向和运动与环境湍流程度相关联。这些观察结果将与数值模型和过去的研究进行比较，以探索粒子沉降速度在低湍流情况下减慢，在高湍流情况下加速，粒子取向与水平偏差增加的假设。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Numerical weather and climate models are sensitive to descriptions of how fast frozen precipitation falls. Many models still use calculations that are rooted in measurements taken nearly 50 years ago. This award will provide up-to-date information on precipitation fall speed, including the impact of turbulence. The work will be accomplished using a new instrument called the Airborne Particle Imager which is designed to measure 3D velocity and take high resolution photography of the individual particles. The main broader societal impact of the award will be the confirmation or improvement upon the assumptions made by numerical models, which will potentially lead to improved weather forecasts. The lead researcher has provided significant public outreach through snowflake imagery, and the new instrument should improve upon those images. The instrument also has potential interdisciplinary and technology transfer uses. In addition, the award will provide education and training opportunities, including support for a female military veteran.The research team plans an observational and theoretical project to improve understanding of how the turbulent atmosphere affects the fall speed of precipitation. A central aspect of the project will be the development of the Airborne Particle Imager (AIP) which is an update to the current Multi-Angle Snowflake Camera (MASC). The AIP will minimize ambient flow disturbance and add 3D velocity measurements to the MASC's existing capabilities. The AIP will be deployed during the 2019-2020 winter in the Complex Hydrometeor Aerial Locomotion and Image Capture Experiment (CHALICE) with other instruments to relate particle type, orientation, and motions to the degree of ambient turbulence. The observations will be compared to numerical models and past studies to explore the hypothesis that particle settling speed is slowed in low turbulence and accelerated in high turbulence situations, with increased deviation of particle orientation from the horizontal.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.