Droplet Nuclei and Condensed Water Content in Mixed-Phase Clouds

这笔赠款支持Twohy博士参与AIRS II项目(第二联盟结冰研究)，这是一个由美国、加拿大和欧洲的机构和机构合作的项目，其动机是飞机结冰这一重要的实际问题。AIRS实地方案计划于2003-2004年冬季进行，总部设在加拿大蒙特利尔北部的米拉贝尔机场，地面观测网络和地面遥感设备将设在那里。Twohy博士和她的同事将在俄亥俄州克利夫兰起飞的NSF C-130飞机上负责云微物理观测。主要的科学目标是解释在什么情况下过冷滴区域可以形成并继续存在于也可能含有冰晶的云层中。C-130将装备用于测量云的水分和冰含量；冰晶的浓度、大小、习性和密度；形成冰的核的浓度；云凝结核(CCN)的活动谱；以及项目区内和感兴趣的云形成的上游空气中的气溶胶粒子的浓度和特征。Twohy博士将负责两台仪器，一台逆流虚拟冲击器(CVI)和一台云光谱仪和冲击器(CSI)。CVI是一台安装在机身上的仪器，它对直径约8至50微米的云滴和冰晶进行采样和大小调整，并蒸发水，留下可以分析的残留颗粒，以确定液滴和冰晶形成的核的大小和组成。CSI是一种安装在机翼上的新型仪器，可以测量单位体积云的凝结水质量、液滴大小分布和颗粒残留物。这些仪器提供的数据与刚刚在云外测量的气溶胶和CCN相比，将表明哪些气溶胶参与了云的形成，它们混合到云中的程度，以及理论能够在多大程度上根据CCN活动谱预测液滴大小分布。将特别注意大的过冷滴，因为它们是飞机结冰的主要原因。这一研究不仅有助于从根本上理解过冷云的微观物理结构，而且有助于提高航空安全水平。

This grant supports the participation of Dr. Twohy in the AIRS II project (second 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 2003-2004 and based at Mirabel Airport, north of Montreal, Canada, where a surface observing network and ground-based remote-sensing equipment will be located. Dr. Twohy and her 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 drops can form and continue to exist in clouds that may also contain ice crystals. The C-130 will be equipped 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 of where the clouds of interest form. Dr. Twohy will be in charge of two instruments, a counterflow virtual impactor (CVI) and a cloud spectrometer and impactor (CSI). The CVI is a fuselage-mounted instrument that samples and sizes cloud droplets and ice crystals between about 8 and 50 micrometers in diameter and evaporates the water, leaving residual particles that can be analyzed to determine the size and composition of the nuclei on which the droplets and crystals formed. The CSI is a new, wing-mounted instrument that measures the mass of condensed water per unit volume of cloud, the droplet-size distribution, and the particle residue. The data provided by these instruments, when compared with the aerosols and CCN measured just outside the cloud, will indicate which of the aerosols participated in cloud formation, the extent to which they were mixed into the cloud, and the degree to which theory enables the prediction of the drop-size distribution on the basis of the CCN activity spectrum. Special attention will be given to large supercooled drops, because these are a major cause of aircraft icing. The research contributes not only to the fundamental understanding of the microphysical structure of supercooled clouds but also to the advancement of aviation safety.