Laboratory Studies of Ice Initiation Mechanisms in Cumulus Clouds

蒸发冰核（EIN）的有效性将在实验室模拟中研究云滴的形成、充电、蒸发和再夹带在积云中通过冻结水平发展。由于云滴中的有机和无机物质，这种核可能是有效的冰核。云顶电荷积累是电冻结冰核增强的一个来源。对于提议的核连续流实验，云滴将使用实验室混合和云室和伊利诺伊州水调查连续流扩散室系统从云凝结核（CCN）中获得，并从超声波雾化大声水中获得。云滴将使用电晕装置充电，并通过与干燥空气混合而蒸发。结果核的激活（阈值）温度将在冷凝、过冷液滴的存在下测量，这些液滴作为冷凝冻结核作为温度的函数。EIN电冻结模式将通过在几个电荷水平上的测量来评估，并且EIN蒸发冻结模式将从使用比冷冻更温暖和更冷的EIN粒子的测量中推断出来。为了区分接触冻结和冷凝冻结，我们将在冷冻室内利用蒸发云进行一组单独的核活性测量，从而通过电泳增强核的接触，抑制冷凝冻结。一套完整的实验计划使用在研究飞行中收集的雾化云水。另一套完整的实验将使用CCN上形成的云水，使用连续流扩散系统进行相应的化学分析。原子核实验和扩散系统将是可移动的，以便将来可以在不同的地点进行测量。

K. Beard/Abstract 9505298 The effectiveness of evaporation ice nuclei (EIN) will bestudied in laboratory simulations of cloud drop formation, charging, evaporation and reentrainment in cumulus clouds developing through the freezing level. Such nuclei are potentially effective ice nuclei because of organic and inorganic materials in cloud drops. Charge accumulation at cloud top is a source of ice nucleus enhancement by electrofreezing. For the proposed nuclei continuous-flow experiment, cloud drops will be obtained from cloud condensation nuclei (CCN) using laboratory mixing and cloud chambers and the Illinois State Water Survey continuous flow diffusion-chamber system, and from ultrasonic nebulization of aloud water. Cloud drops will be charged using a corona device and evaporated by mixing with dry air. The activation (threshold) temperature of the resultant nuclei will be measured in the presence of condensing, supercooled drops that act as condensation freezing nuclei as a function of temperature. The EIN electrofreezing mode will be evaluated by measurements at several charge levels, and the EIN evaporation-freezing mode will be deduced from measurements using EIN particle generated both warmer and colder than freezing. A separate set of nuclei activity measurements will be made to distinguish contact-freezing from condensation-freezing by using an evaporating cloud in the freezing chamber, so that contact of nuclei is enhanced by phoresis and condensation-freezing is suppressed. A complete set of experiments is planned using nebulized cloud water that has been collected during research flights. Another complete set of experiments will be conducted with cloud-water formed on CCN using the continuous flow diffusion system with corresponding chemical analysis. The nuclei experiment and the diffusion system will be transportable so that measurements can be made at various locations in the future.