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

这项拨款支持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，受到飞机结冰这一重要实际问题的推动。AIRS实地项目计划在2003- 2004年冬季进行，并以加拿大蒙特利尔北部的Mirabel机场为中心，在那里将部署地面观测网络和地面遥感设备。哈雷特博士和他的同事们将在俄亥俄州克利夫兰的国家科学基金会C-130飞机上负责云的微物理观测。主要的科学目标是解释在冰晶可能存在的情况下，过冷云区域能够形成并继续存在的环境。C-130将配备测量云层含水量和冰含量的仪器；冰晶：冰晶的浓度、大小、习性和密度；造冰核的浓度；云凝结核（CCN）的活动谱；以及项目区域内和上游空气中气溶胶颗粒的浓度和特征流入感兴趣的云层。由于人们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：冰核在过冷区域稀缺吗？流入空气中的CCN是否与云颗粒的大小和浓度一致？能否将气溶胶测量结果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？如何预测这些事件呢？这些问题的答案不仅有助于理解过冷云的微观物理学，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.