Ice Nuclei and Ice Initiation in Mid-latitude Clouds in Springtime: Background and Dust-Affected

这个项目的重点是推进对冰核的理解，冰核是导致降水和影响冷云辐射特性的最基本过程之一。由于对云中冰的形成过程了解不足，在模拟降水产生的能力方面存在很大的不确定性。此外，最不为人所知的气溶胶对气候的假设影响之一是对冷云特性的改变，即“冰间接效应”。由于缺乏与对流层中高层有关的条件下能够引发冰形成的粒子浓度的观测资料，妨碍了对这种影响的量化。近年来使用连续流动扩散室在各种环境下收集的冰成核数据有助于阐明冰的间接效应。这些数据表明矿物粉尘作为非均质冰核（IN）的一个重要但高度可变的来源的重要性。通过这项研究，将扩大相对未受扰动的背景对流层IN数据库，并将量化在含尘气团中尘埃颗粒浓度、IN浓度以及对冷云形成和微物理的影响之间的关系。具体来说，IN测量将与两个基于飞机的测量项目联合进行，其目标包括调查波浪云、中层云、孤立积云和卷云中的冰起。这些实验是Ice - l（冰在云实验-层云）和PACDEX（太平洋尘埃实验）。在该研究小组以前研究中开发的方法的基础上，将在飞行计划的背景下使用特定的采样程序来调查冰的形成过程，并将in测量与云中的冰晶浓度联系起来。此外，将测量冰成核粒子的组成，并利用全球气溶胶输送模式的辅助测量和指导，将浓度和组成与气溶胶源联系起来。这两项实地研究都特别强调评估对春季从亚洲到美国的远程尘埃输送的云形成和特性的影响。研究结果有望为混合云和冰相云的数值模式模拟提供信息和改进。该项目的智力价值在于预期的对气溶胶重要亚群的理解的改进，这些气溶胶直接影响冷云特性，间接影响气候。参与实地研究提供了一个前所未有的机会，以确认和增强对云中冰的形成以及与自然或人为来源的气溶胶颗粒的联系的理解。这项工作将通过促进研究生教育和培训，加强研究基础设施，在新的机载平台上测试新的测量能力，并通过与数值建模者的合作，将结果应用于全球气候变化问题，产生更广泛的影响。一名研究生和博士后研究员将参与实地实验，这将涉及来自多所大学和一个国家研究中心的不同学科的科学家之间的合作。最后，这些数据对于解决全球变化和人类活动对气候影响的未解决问题至关重要。预计这项研究的研究将在人类活动对云形成的影响的全球研究以及云解析和全球模式中改进的参数化的发展中找到广泛的应用。

This project focuses on advancing understanding of ice nucleation, one of the most basic processes leading to precipitation and impacting the radiative properties of cold clouds. Poor understanding of ice initiation processes in clouds results in large uncertainties in the ability to model precipitation production. Furthermore, one of the least understood postulated climate effects of aerosols is the modification of cold-cloud properties, the "ice indirect effect". Quantification of this effect is hampered by the lack of observational data on concentrations of particles capable of initiating ice formation at conditions relevant to the mid-to-upper troposphere. Data on ice nucleation collected using continuous flow diffusion chambers in a variety of settings in recent years have contributed to elucidation of the ice indirect effect. These data have indicated the importance of mineral dust as a significant, but highly variable, source of heterogeneous ice nuclei (IN). Through this research, the database on relatively unperturbed background tropospheric IN will be expanded and, in dust-laden air masses, relationships between dust particle concentrations, IN concentrations, and impacts on cold cloud formation and microphysics will be quantified. Specifically, IN measurements will be made in association with two aircraft-based measurement programs having objectives that include the investigation of ice initiation in wave clouds, mid-level layer clouds, isolated cumuli and cirrus clouds. These experiments are ICE-L (Ice in Clouds Experiment - Layer clouds) and PACDEX (PACific Dust Experiment). Building on methodologies developed in previous studies by this research group, specific sampling procedures will be used within the context of flight plans to investigate ice formation processes and to relate IN measurements to ice crystal concentrations in clouds. Further, the compositions of ice nucleating particles will be measured and both concentrations and compositions will be related to aerosol sources, using supporting measurements and guidance from global aerosol transport models. Both field studies have a particular emphasis on evaluating the impact on cloud formation and properties of long-range dust transport from Asia to the U.S. in Spring. Results are expected to inform and improve numerical model simulations of mixed- and ice-phase clouds. The intellectual merit of the project lies in the expected improvement in understanding the important sub-population of aerosols that affect cold cloud properties directly and climate indirectly. Participation in the field studies offers an unprecedented opportunity to confirm and augment understanding of ice initiation in clouds and links to aerosol particles of natural or manmade origin. This work will have broader impacts through promoting graduate education and training, enhancing research infrastructure, testing new measurement capabilities on a new airborne platform, and through collaboration with numerical modelers, application of results toward global climate change issues. A graduate student and post-doctoral researcher will participate in the field experiments, which will involve collaborations amongst scientists in different disciplines from multiple universities and from a national research center. Finally, these data are of critical importance to unresolved issues in global change and climate impacts of anthropogenic activities. It is expected that the research of this research will find broad applications as diverse as global studies of the effects of human activities on cloud formation and development of improved parameterizations in cloud resolving and global models.