Laboratory and Modeling Studies of the Growth Efficiency of Vapor Grown Ice

卷云存在于极度寒冷的条件下，那里几乎没有水分。 构成卷云和其他冷云的冰粒的生长途径是复杂的，并且在理解这些晶体如何增加大小和质量方面存在差距。 该奖项将重点关注蒸汽生长，这是水蒸气沉积到冰晶上的过程。 研究团队运行一个非常专业的云室，可以在极冷的温度下测试单个晶体的生长。 这项研究的主要好处是提供了一个检查的数值模式，模拟冷云，并提供输入参数，这些模型。 这将对与社会相关的天气预报和气候预测产生影响。 该项目还将有助于培养下一代科学家，并提供有趣的外展机会，以提高公众的科学素养。研究小组将继续研究大气冷云中冰晶的生长。 这项工作的重点是解决一个关键的差距，在非常冷的温度下的沉积系数的理解。 本工作将利用悬浮扩散室和垂直流悬浮室在不同条件下生长冰晶。 实验室数据将与现有的和新的理论模型协同使用，以获得云模型的输入参数。 这项工作的具体目标是确定：1）均匀冷冻液滴的沉积系数比非均匀冷冻液滴覆盖更大的范围是否是稳健的结果，2）从悬浮扩散室提取的特征过饱和度是否遵循在低于-40 ℃的温度下从先前测量估计的值，3）如果生长转变对于均匀冻结的液滴是唯一的，以及是否可以构建该过程的模型，4）动力学的幂律参数化-扩散限制生长可以根据实验室数据的拟合来构建。该奖项反映了NSF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。

Cirrus clouds exist in extremely cold conditions where there is very little moisture. The pathways for the growth of ice particles that make up cirrus and other cold clouds is complex, and there are gaps in the understanding of how these crystals increase in size and mass. This award will focus on vapor growth, which is the process in which water vapor is deposited onto ice crystals. The research team runs a very specialized cloud chamber that allows for the testing of the growth of individual crystals at extremely cold temperatures. The main benefit of this research is to provide a check on numerical models that simulate cold clouds and to provide input parameters to those models. This will have an impact on societally-relevant weather forecasts and climate projections. The project will also help to train the next generation of scientists and provide interesting outreach opportunities to increase public science literacy.The research team will continue their studies into the growth of ice crystals in atmospheric cold clouds. The focus of the work is on addressing a critical gap in the understanding of the deposition coefficient at very cold temperatures. The work will make use of a levitation diffusion chamber and vertical flow levitation chamber to grow ice crystals in different conditions. The lab data will be used synergistically with existing and new theoretical models to derive input parameters for cloud models. The specific objectives of the work are to determine: 1) Whether it is a robust result that the deposition coefficients cover a larger range for homogeneously frozen drops than heterogeneously frozen drops, 2) Whether characteristic supersaturations extracted from the levitation diffusion chamber follow the values estimated from prior measurements at temperatures below -40C, 3) If growth transitions are unique to homogeneously frozen drops and whether a model of the process can be constructed, and 4) Whether a power law parameterization of kinetics-diffusion limited growth can be constructed based on fits to laboratory data.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.