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

普渡大学ATM-0312439 Lasher-TRapp项目题目：AIRS期间冬季层状云中超巨型粒子形成的过冷大液滴IIT这笔赠款支持Lasher-TRapp博士参与AIRS II项目(第二联盟结冰研究)，该项目是美国、加拿大和欧洲机构的合作项目，动机是飞机结冰这一重要的实际问题。AIRS实地计划计划于2003-04年冬季在加拿大蒙特利尔北部的米拉贝尔机场进行，地面观测网络和地面遥感设备将设在那里。拉舍尔-特拉普博士和她的同事们将负责在俄亥俄州克利夫兰运行的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可以形成并继续存在的情况，尽管也可能存在冰晶。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。Lasher-TRapp博士将与各种光学和撞击粒子传感器合作，以确定“超巨型”粒子(UGP)的浓度、大小和组成(固体或液体)--那些等效球径大于约10微米的粒子。众所周知，这种粒子有时会通过云层中的凝聚-合并过程在雨的形成中发挥作用，这些云层太热，不足以容纳冰，但人们还没有对它们进行系统的研究，甚至还没有在含有冰晶或过冷水的云层中观察到它们。据推测，UGP可能解释了最近报道的冬季云层中超过50微米的过冷水滴--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，它将提供从小于10微米到0.6毫米的颗粒物信息。将对数据进行分析，以确定在云外测量的UGP浓度与云内大型过冷滴浓度之间是否存在对应关系。如果是这样的话，UGP的存在可能解释了为什么过冷的水滴即使在过冷的温度下也能长得很大，在过冷的温度下，它们可能会冻结，或者，如果冰晶也存在，随着晶体从蒸汽中扩散长大，它们会蒸发。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。

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.