Turbulence--Cloud Interactions: Laboratory and Field Studies

我们对云的物理学的大多数处理的一个基本的潜在假设是，水滴在亚网格尺度上以完全随机的方式分布在空间中。一段时间以来，人们已经认识到，在云边缘夹带发生的地方，这一假设显然是违反的，但湍流对云内部液滴空间分布的影响，从而对我们理解云的物理过程，最近才受到严格审查。从理论和模拟研究的建议，湍流应该“集群”滴已被证明是难以确认的云观测，主要是因为采样问题与现场设备。由主要研究人员进行的风洞实验似乎为该环境中的集群提供了一些支持。该补助金支持继续进行实验室研究，以调查湍流对特征良好的条件下液滴空间分布的影响，特别强调如何将其应用于碰撞合并过程。主要研究人员将使用高空间分辨率，高数字分辨率，短曝光电荷耦合器件（CCD）相机，使测量的三维空间分布的液滴使用内联全息在实验室湍流室。湍流室将更大，使得内部的湍流雷诺数将更接近大气中的湍流雷诺数，并且能量耗散率将类似于大气中的湍流雷诺数。室内的流动将采用粒子图像测速仪进行表征。液滴的空间分布以及湍流特征允许研究聚集对液滴尺寸和湍流强度的依赖性。从德国马克斯·普朗克动力学和自组织研究所借来的高速数码相机的进一步增加将允许测量液滴相对速度分布，从而关闭评估广义收集内核所需的测量。实验室的结果将进行评估，并扩展到高湍流雷诺数制度，在自然云中使用相同的内联holographic system.Broader影响：这项工作具有广泛的潜在影响，因为它跨越了大气科学和工程多相流领域。主要研究者与工程多相流社区的人们有很强的合作关系，因此受益于多相流中更大的工程专业知识的大气科学社区，并充当管道。这项实验工作是对一个理论和建模工作已经超过我们观测能力的领域的重要贡献。主要研究者有一个良好的记录与本科生，他希望继续与此补助金，并将支持一个研究生和一个博士后学生工作。

A basic underlying assumption for most of our treatment of the physics of clouds is that drops are distributed in space in a perfectly random manner at sub-grid scales. It has been recognized for some time now that this assumption is clearly violated at cloud edges where entrainment takes place, but the impact of turbulence on drop spatial distributions in cloud interiors, and hence on our understanding of cloud physical processes, has only recently come under intensive scrutiny. The suggestion from theoretical and modeling studies that turbulence should "cluster" drops has proven difficult to confirm from in-cloud observations, mostly because of sampling problems with in situ devices. Wind tunnel experiments performed by the principle investigator seem to provide some support for clustering in that environment. This grant supports continued laboratory studies to investigate the impact of turbulence on drop spatial distributions in well-characterized conditions, with particular emphasis on how this applies to the collision-coalescence process. The principle investigator will use high spatial resolution, high digital resolution, and short exposure Charge Coupled Device (CCD) cameras to make measurements of the three-dimensional spatial distribution of drops using inline holography in a laboratory turbulence chamber. The turbulence chamber will be larger such that the turbulence Reynolds number inside will be closer to and the energy dissipation rates similar to those found in the atmosphere. The flow inside the chamber will be characterized with particle image velocimetry. The spatial distribution of drops, together with the turbulence characterization, allows for investigations of the dependence of clustering on drop size and turbulent intensity. A further addition of a high speed digital camera, loaned from the Max Planck Institute for Dynamics and Self Organization in Germany, will allow measurement of the drop relative velocity distribution, thus closing the measurements needed to evaluate the generalized collection kernel. The laboratory results will be evaluated, and extended to high turbulence Reynolds number regimes, in natural clouds using the same inline holographic system.Broader Impacts: This work has broad potential impact as it spans the fields of atmospheric sciences and engineering multiphase flows. The principle investigator has strong collaborative ties with people in the engineering multiphase flow community, and thus benefits from and acts as a conduit to the atmospheric sciences community of the greater engineering expertise in multiphase flows. This experimental work is a critical contribution to a field where theoretical and modeling work has outpaced our observational abilities. The principle investigator has a well-established track record working with undergraduate students, which he hopes to continue with this grant, and will also support one graduate and one post-doctoral student.