Combined Laboratory and Modeling Studies of Ice Vapor Growth at Low Temperatures

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。 最近的实验室测量表明，沉积系数，生长效率的措施，是小冰晶，它取决于过饱和度小。模拟研究表明，模拟的卷云中的冰浓度和过饱和度，以及混合相云的冰川化率，敏感地依赖于冰的增长率。本文的工作旨在促进对冷大气中冰蒸气增长的理解。智力价值：这项综合研究将产生实验室和模拟研究之间的协同作用。这项工作将集中在冰从气相生长的目的是减少在过去的测量的沉积系数的不确定性。 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，温度和压力的函数。这些数据可用于探索沉积系数对类似于大气中冰晶经历的环境条件的依赖性。 此外，这些数据也可以用来批评新的和常用的蒸汽增长方法，并限制云模型中使用的参数化。 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。这项实验室建模研究所提供的协同作用将有助于为人们对冰过程知之甚少的问题提供新的线索，这些过程目前限制了我们准确预测云演变的能力。更广泛的影响：这项研究可能对大气科学和社会产生广泛的影响。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。 这项工作也可以展示给不同的观众，包括K-12学生。 此外，还计划利用学院资源继续开发包裹微物理模型，作为课堂教学工具。

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. Recent laboratory measurements suggest that the deposition coefficient, a measure of growth efficiency, is small for small ice crystals and that it depends on the supersaturation. Modeling studies show that simulated ice concentrations and supersaturations in cirrus clouds, as well as the rates of glaciation of mixed-phase clouds, depend sensitively on ice growth rates. The work herein seeks to advance understanding of ice vapor growth in cold atmospheric clouds.Intellectual merit:This integrated study will produce a synergy between laboratory and modeling research. The work will focus on ice grown from the vapor phase with the intention being to reduce uncertainties in past measurements of the deposition coefficient. 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 pressure. These data can be used to explore the dependence of the deposition coefficient on environmental conditions similar to those ice crystals experience in the atmosphere. Moreover, these data can also be used to critique new and commonly used vapor growth methods, and constrain the parameterizations used 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 help 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 work can also be demonstrated to diverse audiences including K-12 students. Moreover, continue development of parcel microphysical models as classroom teaching tools using College resources is planned.