Combined Laboratory and Modeling Studies of Ice Vapor Growth

含冰云可以存在于低层大气中的任何地方。 对流层上部的卷云就是一个常见的例子，它们完全或大部分由冰组成。 低层云可能含有液体和冰，而中层云在大多数纬度都含有一些液体。 冰晶呈现出各种复杂的形状，仅通过蒸汽扩散就可以变大。 冰的存在使云的微观物理学、动力学和辐射之间的联系变得复杂，使得精确的云模拟变得困难。冰从气相生长被证明是这一链条中关键但令人困惑的一环。 以前的实验室测量表明，沉积系数，生长效率的衡量标准，是非常小的冰晶。 此外，现在看来，长宽比预测可能是关键的模拟含冰云，但竞争的假设存在关于质量分布的晶体面在生长过程中。模拟研究表明，模拟的卷云冰浓度和过饱和度，以及混合相云的冰川化率，敏感地依赖于冰的增长率。智力上的优点。 这项综合研究将集中在冰的增长，从汽相的意图，以减少在过去的测量和测试假设的不确定性，关于分子的掺入和纵横比的演变。实验室方法利用电动悬浮将冰颗粒与系统壁隔离，并允许在精确控制的条件下跟踪颗粒生长。 新的测量蒸汽增长率将获得的大小，过饱和度，温度和纵横比的函数。 这些数据将被用来测试竞争的增长假设和约束云模型中的参数化。 冰晶生长理论和数值模型将为实验室工作提供指导，帮助解释实验结果，并为将实验室结果扩展到云系统提供框架。 这项实验室模拟研究所提供的协同作用将为目前限制我们准确预测云演变的能力的知之甚少的冰过程提供新的启示。 这项研究对大气科学和社会具有潜在的广泛影响。 在所有的模拟尺度上，含冰云的模拟都存在很大的不确定性，这表明改进模型中冰蒸气生长参数化的后果可能在科学上具有深远的影响。 这项研究将培养研究生，并让高年级本科生接触现代研究。 该研究和实验室也可以向不同的观众展示，包括K-12学生。

Ice-containing clouds can exist anywhere within the lower atmosphere. Cirrus clouds in the upper troposphere are a common example, being composed entirely or mostly of ice. Low-level clouds may contain both liquid and ice while mid-level clouds contain some liquid at most latitudes. Ice crystals take on a variety of complex shapes and can grow large by vapor diffusion alone. The presence of ice complicates the links between cloud microphysics, dynamics, and radiation, making accurate cloud simulations difficult. Ice growth from the vapor phase proves to be a key but perplexing link in this chain. Previous laboratory measurements suggest that the deposition coefficient, a measure of growth efficiency, is very small for small ice crystals. In addition, it now appears that aspect ratio prediction may be critical for the simulation of ice-containing clouds; however competing hypotheses exist regarding mass distribution on the crystal faces during growth. Modeling studies show that simulated ice concentrations and supersaturation in cirrus clouds, as well as the rates of glaciation of mixed-phase clouds, depend sensitively on ice growth rates. Intellectual merit. This integrated study will focus on ice growth from the vapor phase with the intention to reduce uncertainties in past measurements and to test hypotheses regarding molecular incorporation and aspect ratio evolution. The laboratory methods make use of electrodynamic levitation to isolate ice particles from system walls and permit particle growth to be followed under precisely controlled conditions. New measurements of vapor growth rates will be obtained as functions of size, supersaturation, temperature, and aspect ratio. These data will be used to test competing growth hypotheses and constrain the parameterizations in cloud models. Ice crystal growth theories and numerical models will provide guidance to the laboratory work, help interpret experimental findings, and provide a framework for extending lab results to cloud systems. The synergism afforded by this laboratory-modeling study will shed new light on poorly understood ice processes that are currently limiting our ability to accurately predict cloud evolution.Broader Impacts. This research has potentially broad impacts on the atmospheric sciences and society. Large uncertainties exist in simulations of ice-containing clouds at all modeling scales indicating that the consequences of improving ice vapor growth parameterizations in models could be scientifically far-reaching. The research will train graduate students and give advanced undergraduate students exposure to modern research. The research and laboratory can also be demonstrated to diverse audiences, including K-12 students.