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

春季中纬度云中的冰核和冰起始：背景和沙尘影响

• 批准号: 0611936
• 负责人: Paul DeMott
• 金额: --
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-11-01 至 2010-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0611936&HistoricalAwards=false
• 关键词: Ice; Nuclei; Initiation; Mid; latitude

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.

该项目的重点是推进对冰核的理解，这是导致降水和影响冷云的辐射特性的最基本过程之一。对云中冰开始过程的了解不足，导致建模降水产生的能力大大不确定性。此外，气溶胶的理解最低的气候效应之一是修饰冷云特性，即“冰间接效应”。缺乏对能够在与中次对流层相关的条件下启动冰形成的颗粒的浓度的观察数据，从而阻碍了这种效果的量化。近年来，在各种环境中使用连续流动扩散室收集的冰核数据有助于阐明冰的间接效应。这些数据表明，矿物灰尘是异质冰核的重要但高度可变的来源（IN）的重要性。通过这项研究，将扩展相对不受干扰的对流层的数据库，并在尘埃空气质量中扩展，将灰尘浓度，浓度之间的关系以及对冷云形成和微物理学的影响。具体而言，在测量中将与两个基于飞机的测量程序相关，其中包括对波云中的冰开始，中层层云，孤立的库利和卷心云进行研究。这些实验是ICE -L（云实验中的冰 - 层云）和PACDEX（Pacific Dust实验）。在该研究小组先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抽样程序，以研究冰层形成过程并与云中的冰晶体浓度进行测量。此外，将使用全球气溶胶传输模型的支撑测量和指导来测量冰核颗粒的组成，并将浓度和组成与气溶胶源相关。两项现场研究都特别强调评估对春季从亚洲到美国的云形成的影响和远程尘埃运输的影响。结果有望为混合和冰相云的数值模型仿真提供信息和改善。该项目的智力优点在于预期的改善在理解直接和间接影响寒冷云特性的气溶胶的重要亚群中。参与现场研究提供了一个前所未有的机会，可以确认和增强对云中的冰开始以及与天然或人为起源的气溶胶颗粒的联系。这项工作将通过促进研究生教育和培训，增强研究基础设施，在新的空降平台上测试新的测量能力以及与数字建模者的合作，将结果应用于全球气候变化问题，从而产生更广泛的影响。研究生和博士后研究人员将参加现场实验，这将涉及来自多个大学和国家研究中心不同学科的科学家之间的合作。最后，这些数据对于在全球变化和人为活动的气候影响中未解决的问题至关重要。预计这项研究的研究将发现与全球活动对人类活动对云形成的影响以及改进云解决和全球模型中参数化的开发的多样化一样多样化。