Aircraft Study of the Structure and Evolution of Supercooled and Mixed- Phase Clouds

该补助金支持Hallett博士和其他研究人员参与AIRS II项目（联盟结冰研究），这是美国，加拿大和欧洲机构和机构的合作，旨在解决飞机结冰的重要实际问题。 AIRS实地计划定于2003-04年冬季进行，中心设在加拿大蒙特利尔北部的米拉贝尔机场，那里将设有地面观测网络和地面遥感设备。 Hallett博士和他的同事将负责在俄亥俄州克利夫兰的NSF C-130飞机上进行云微物理观测。 主要的科学目标是解释过冷云区域形成并继续存在的环境，尽管冰晶也可能存在。 C-130将配备用于测量云的含水量和冰含量的仪器;冰晶的浓度，大小，习性和密度;冰形成核的浓度;云凝结核（CCN）的活动谱;以及项目区域内和流入感兴趣的云的上游空气中的气溶胶颗粒的浓度和特性。 由于对过冷云的结构和演化知之甚少，这种方法在很大程度上是探索性的。 实验将被设计来回答以下问题：在过冷区域冰核稀缺吗？ 入流空气中的云凝结核与云粒子的大小和浓度是否一致？ 气溶胶的测量结果是否可以合成用于数值云模式，从而进一步了解过冷云的持久性？ 过冷云持续存在的气象条件是什么？ 如何预测此类事件？ 对这些问题的回答不仅有助于理解过冷云的微观物理，而且有助于提高航空安全。

This grant supports the participation of Dr. Hallett and other researchers in the AIRS II project (Alliance Icing Research Study), a collaboration of American, Canadian, and European agencies and institutions motivated by the important practical problem of aircraft icing. The AIRS field program is scheduled for the winter of 2003-04 and centered at Mirabel Airport, north of Montreal, Canada, where a surface observing network and ground-based remote-sensing equipment will be located. Dr. Hallett and his colleagues will be responsible for cloud microphysical observations aboard the NSF C-130 aircraft operating out of Cleveland, Ohio. The main scientific objective is to explain the circumstances by which regions of supercooled cloud can form and continue to exist though ice crystals may also be present. The C-130 will be equipped with instruments for measuring the water content and ice content of clouds; the concentration, size, habit, and density of ice crystals; the concentration of ice-forming nuclei; the activity spectrum of cloud condensation nuclei (CCN); and the concentration and characteristics of aerosol particles both within the project area and in the air upstream that flows into the clouds of interest. Because little is known of the structure and evolution of supercooled clouds, the approach is largely exploratory. Experiments will be designed to answer the following questions: Are ice nuclei scarce in the supercooled regions? Are the CCN in the inflowing air consistent with cloud particle sizes and concentrations? Can the aerosol measurements be synthesized for use in numerical cloud models that may give further insight on the persistence of supercooled clouds? What are the meteorological conditions under which supercooled clouds persist? How might such events be predicted? Answers to these questions contribute not only to the understanding of the microphysics of supercooled clouds but also to the advancement of aviation safety.