Collaborative Research: Laboratory and Ground-Based Studies Addressing Unresolved Aspects of Atmospheric Ice Nucleation

合作研究：实验室和地面研究解决大气冰核形成的未解决问题

• 批准号: 0841602
• 负责人: Paul DeMott
• 金额: $ 78.24万
• 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: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0841602&HistoricalAwards=false
• 关键词: Collaborative; Research; Laboratory; Ground; Based

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project focuses on advancing understanding of critical issues in atmospheric ice nucleation, one of the most basic processes affecting precipitation and impacting the radiative properties of cold clouds. Incomplete understanding of ice initiation processes in clouds results in large uncertainties in the ability to model clouds and precipitation. Under prior support, the Principal Investigators (PIs) have made advancements in the area of real-time measurement of heterogeneous ice nuclei (IN) and in understanding the role of different aerosol particle types capable of initiating ice formation in the atmosphere. These measurements highlight significant remaining questions. For example, atmospheric studies have emphasized the importance of mineral dust as a significant IN source, but laboratory studies of natural dust particles up to 1 micron in size have shown no evidence for IN activity warmer than about -15 degrees Celsius. The second most prevalent IN composition that has been identified in the atmosphere are carbonaceous particles, but their sources are unresolved. Biological aerosols represent potential sources for primarily carbonaceous IN, but their number concentrations are poorly observed by existing measurement methods. Finally, apparent degradation of IN efficiency in polluted air has been observed but there is little fundamental basis for understanding the impacts of atmospheric processing on IN activation. The Principal Investigators will use laboratory studies to investigate ice formation by natural dusts at sizes up to 5 microns to quantify the relation between IN activation temperature and mineral dust particle size for different mineralogical types. They also will quantify the changes in IN activation properties after exposure to realistic degrees of atmospheric processing. Examinations of supermicron-sized particles as ice nuclei in the PIs' continuous flow ice nuclei instrument is made possible by application of a new particle phase-discrimination detector (PPD) that identifies ice crystals and aerosol particles by their spatial scattering patterns rather than optical size alone. Use of the PPD will permit exploration of the impact of evaporation of IN containing droplets on ice nucleation, of interest due to inferences that this process spawns primary or secondary ice nucleation. The PIs will investigate the number concentrations of biological ice nuclei through studies that utilize a real-time IN detector and application of real-time mass spectrometric or post-application of microbiological methods (DNA analyses) on activated and collected IN. Using this approach, IN-active bacteria are identified at specific temperature and humidity conditions, enabling an assessment of their role across the full temperature regime of tropospheric clouds. After refining procedures through laboratory studies, The PIs will apply these methods to quantify the proportion of ambient IN, as a function of temperature, that are of biological origin. The opportunity also exists to identify heretofore unrecognized biological IN. The intellectual merit of the project lies in the opportunity to confirm and augment present understanding and quantification of ice initiation in clouds and its relation to the specific properties of key atmospheric source populations of ice nuclei. The PIs will quantify ice formation by IN across their atmospherically-relevant size and temperature range, apply advanced techniques for detecting IN composition, determine the impacts of atmospheric processing on IN activation, and explore ice formation mechanisms. Nucleation parameterization development for numerical modeling studies may be advanced using results from this research. This work will have broader impacts through promoting graduate education and training, enhancing research infrastructure, development and testing of new instrumentation and methods, application of results toward global climate change issues through associated numerical modeling studies, and fostering cross-disciplinary research between the atmospheric and biological sciences. The PIs will encourage application of results through related modeling studies, collaboration with other researchers, and participation in working groups. Graduate students and a postdoctoral scientist will participate and the work will involve collaborations across multiple disciplines and universities. Results will be disseminated via a project web site, publications, and participation in conferences. Finally, these data are of critical importance to unresolved impact of aerosols on ice clouds and global climate.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目侧重于推进对大气冰成核关键问题的理解，这是影响降水和影响冷云辐射特性的最基本过程之一。对云中冰的形成过程的不完全理解导致了云和降水模拟能力的很大不确定性。 在先前的支持下，主要研究人员（PI）在实时测量异质冰核（IN）和了解能够在大气中引发冰形成的不同气溶胶颗粒类型的作用方面取得了进展。这些测量突出了重大的遗留问题。 例如，大气研究强调了矿物粉尘作为重要IN来源的重要性，但对尺寸达1微米的天然粉尘颗粒的实验室研究显示，没有证据表明IN活动温度高于约-15摄氏度。大气中第二种最普遍的IN成分是碳质颗粒，但其来源尚未解决。 生物气溶胶主要是碳质IN的潜在来源，但现有的测量方法观察到的数量浓度很差。 最后，已观察到污染空气中IN效率的明显下降，但了解大气处理对IN活化的影响几乎没有基本依据。主要研究人员将使用实验室研究来研究大小不超过5微米的天然粉尘的冰形成，以量化不同矿物类型的IN活化温度和矿物粉尘粒度之间的关系。 他们还将量化暴露于现实程度的大气处理后IN活化特性的变化。 在PI的连续流冰核仪器中检查作为冰核的超微米级颗粒是通过应用新的颗粒相位鉴别检测器（PPD）来实现的，该检测器通过空间散射图案而不是仅仅通过光学尺寸来识别冰晶和气溶胶颗粒。PPD的使用将允许探索含IN液滴的蒸发对冰成核的影响，由于推断该过程产生初级或次级冰成核，因此感兴趣。 PI将通过利用实时IN检测器和应用实时质谱法或对激活和收集的IN应用后微生物方法（DNA分析）的研究来调查生物冰核的数量浓度。 使用这种方法，在特定的温度和湿度条件下识别IN活性细菌，从而能够评估它们在对流层云的整个温度状态中的作用。 在通过实验室研究完善程序后，PI将应用这些方法来量化环境IN的比例，作为温度的函数，生物来源。还存在鉴定迄今未被认识的生物IN的机会。该项目的智力价值在于有机会确认和增强目前对云中冰的形成及其与关键大气源冰核种群的具体性质的关系的理解和量化。PI将量化冰的形成，通过在其大气相关的大小和温度范围内，应用先进的技术来检测IN成分，确定大气处理对IN激活的影响，并探索冰的形成机制。 核参数化的发展，数值模拟研究可能会提前使用本研究的结果。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，开发和测试新的仪器和方法，通过相关的数值模拟研究将结果应用于全球气候变化问题，以及促进大气和生物科学之间的跨学科研究，产生更广泛的影响。 PI将通过相关的建模研究，与其他研究人员的合作以及参与工作组来鼓励结果的应用。 研究生和博士后科学家将参与，工作将涉及多个学科和大学的合作。将通过项目网站、出版物和参加会议传播成果。最后，这些数据对于解决气溶胶对冰云和全球气候的影响至关重要。