Laboratory Studies of Ice Initiation Mechanisms in Cumulus Clouds

K.Beard/摘要9505298蒸发冰核(EIN)的有效性将在实验室模拟通过冰层发展的积云中的云滴形成、充电、蒸发和再卷吸中进行。由于云滴中的有机和无机物质，这样的原子核可能是有效的冰核。云顶的电荷积累是电冻强化冰核的一个来源。对于拟议的核连续流实验，云滴将从云凝结核(CCN)中使用实验室混合和云室和伊利诺伊州立大学水调查连续流扩散室系统，以及从高声水的超声波雾化获得。云滴将使用电晕装置充电，并与干燥的空气混合蒸发。作为温度函数的凝结过冷液滴的存在，将测量生成的原子核的激活(阈值)温度。EIN电冷冻模式将通过在几个电荷水平上的测量来评估，而EIN蒸发-冷冻模式将通过使用产生的比冻结更热和更冷的EIN粒子的测量来推断。另一套核活度测量将通过在冷冻室中使用蒸发云来区分接触冻结和凝结冻结，从而通过电泳法加强原子核的接触，抑制凝结冻结。一套完整的实验计划使用在研究飞行中收集的雾化云水进行。另一套完整的实验将使用连续流扩散系统和相应的化学分析对CCN上形成的云水进行。原子核实验和扩散系统将是可运输的，这样将来就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.