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。许多模型仍然使用基于近50年前测量结果的计算方法。该合同将提供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速度并拍摄单个粒子的高分辨率照片。该奖项的主要更广泛的社会影响将是对数值模型所做假设的确认或改进，这将有可能改善天气预报。首席研究员通过雪花图像提供了重要的公众宣传，新仪器应该在这些图像的基础上进行改进。该工具还具有跨学科和技术转让的潜在用途。此外，该奖项还将提供教育和培训机会，包括为一名女退伍军人提供支持。研究小组计划进行一个观测和理论项目，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机载粒子成像仪（AIP）的开发，这是对当前多角度雪花相机（MASC）的更新。AIP将最大限度地减少环境流动干扰，并在MASC现有功能的基础上增加3D速度测量。AIP将在2019-2020年冬季部署在复杂水流星空中运动和图像捕获实验（CHALICE）中，与其他仪器一起将粒子类型、方向和运动与环境湍流程度联系起来。将观测结果与数值模型和过去的研究进行比较，以探索低湍流情况下颗粒沉降速度减慢而高湍流情况下颗粒沉降速度加快的假设，并增加颗粒方向与水平的偏差。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.