Supercooled Large Drop Formation by Ultragiant Particles in Wintertime Stratiform Clouds during the Second Alliance Icing Research Study (AIRS II)

AIRSII期间冬季层状云中由超巨型粒子形成的过冷大液滴该基金支持Lasher-Trapp博士参与AIRS II项目（第二次联盟结冰研究），该项目是由美国、加拿大和欧洲的机构和研究所合作完成的，其目的是解决飞机结冰这一重要的实际问题。 AIRS的实地方案定于2003-04年冬季在加拿大蒙特利尔北部的米拉贝尔机场进行，那里将设有地面观测网络和地面遥感设备。 Lasher-Trapp博士和她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;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;以及项目区域内和感兴趣的云形成的上游空气中气溶胶颗粒的浓度和特性。 Lasher-Trapp博士将与各种光学和撞击颗粒传感器合作，以确定“超巨型”颗粒（UGP）的浓度，尺寸和成分（固体或液体）-那些等效球形直径大于约10微米的颗粒。 已知这些粒子有时会在太温暖而不含冰的云中通过凝结-聚合过程形成雨，但它们尚未被系统地研究，甚至在含有冰晶或过冷水的云中观察到。 已经证实，UGP可以解释最近报道的冬季云层中大于50微米的过冷水滴的观测结果-水滴大到足以成为飞机结冰的主要原因。 AIRS II计划进行测量，将提供从小于10微米到0.6毫米的颗粒信息。将对数据进行分析，以确定云外测量的UGP浓度与云内大型过冷液滴浓度之间是否存在对应关系。 如果是这样的话，UGP的存在可以解释过冷液滴如何能够生长到大尺寸，即使在过冷温度下，它们可能会冻结，或者如果冰晶也存在，随着晶体通过从蒸汽中扩散而生长而蒸发。 该研究不仅有助于对过冷云微物理结构的基本认识，而且有助于提高航空安全。

AbstractATM-0312439Lasher-Trapp, SoniaPurdue UniversityTitle: Supercooled Large Drop Formation by Ultragiant Particles in Wintertime Stratiform Clouds During AIRS IIThis grant supports the participation of Dr. Lasher-Trapp 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 2003-04 and based at Mirabel Airport, north of Montreal, Canada, where a surface observing network and ground-based remote-sensing equipment will be located. Dr. Lasher-Trapp 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 cloud can form and continue to exist though ice crystals may also be present. 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. Lasher-Trapp will work with various optical and impaction particle sensors to determine the concentration, sizes, and composition (solid or liquid) of "ultragiant" particles (UGP) - those with equivalent spherical diameters greater than about 10 micrometers. Such particles are known sometimes to play a part in the formation of rain by the condensation-coalescence process in clouds that are too warm to contain ice, but they have not been systematically studied or even observed in clouds containing ice crystals or supercooled water. It has been conjectured that UGP may account for recently reported observations of supercooled drops larger than 50 micrometers in wintertime clouds - drops large enough to be a major cause of aircraft icing. Measurements are planned in AIRS II that will provide information on particles ranging from smaller than 10 micrometers up to 0.6 mm. The data will be analyzed to determine if there is a correspondence between the concentration of UGP measured outside of the cloud and the concentration of large supercooled drops within. If so, the presence of UGP may explain how supercooled drops can grow to large size even at the supercooled temperatures where they might be expected to freeze or, if ice crystals are also present, to evaporate as the crystals grow by diffusion from the vapor. The research contributes not only to the fundamental understanding of the microphysical structure of supercooled clouds but also to the advancement of aviation safety.