CAREER: The Role of Ice-Nucleating Particles and Their Feedback on Clouds in Warming Arctic Climate

_________________________________________________________________________________________________________________________北极正在迅速变暖--比世界其他地区更快。已经为这种所谓的北极极地放大提出了一些过程。虽然众所周知，海冰在反射太阳辐射和改变地球表面温度方面发挥了重要作用，但其他过程的作用很难量化。特别是，北极地区与冰核粒子(INP；低于-20°C的百万个气溶胶粒子中只有几个)和涉及冰的云有关的大气机制的贡献仍然不确定。该项目旨在通过调查北极大西洋地区INP的来源(天然/人工)、大气丰度/预算、化学成分和物理性质来填补这一空白。此外，在数值浓度、化学成分和INP来源方面的测量不确定度很大，这对模拟真实生活现象是有问题的。这项研究的目标是将测量的不确定性降至最低，并通过一系列研究解决这一关键缺陷，这些研究涉及直接收集冰核颗粒及其残留物。为了表征北极冰核粒子的特性，将使用一种新型的便携式冰核实验室和冷台支撑的液滴冻结实验来获得空气中粒子样品的冻结温度谱。一种新的惯性冰粒分离技术将用于收集与北极冰云相关的冰晶残留物。随后对冰晶残留物和周围气溶胶颗粒进行的离线显微光谱表征将揭示气溶胶物理化学性质在冰核形成过程中对颗粒大小的相对重要性。最终，这项研究的INP和冰晶残留物的测量将被参数化并转化为描述作为温度、其组成、水活度参数和其他物理化学性质的函数的颗粒的时间分辨冻结能力。最后，研究和教育的融合是这个项目最重要的目标。该项目将有两名研究生和几名本科生参与研究、课程开发和推广，因为这些是有助于他们专业发展的学习经验。该项目还将开发与拟议研究相结合的实践课程单元，向公众讲授环境和气候科学，促进大学课程和培训未来的科学家。目前，北极实地数据中关于气温在-15℃以上的大气成冰粒子的丰度和组成的严重不足。来自北极大西洋地区的高温INP的最新表示将促进大气模型界对冰核形成过程及其在地球能量平衡中的形成的了解。该项目还旨在提供可靠的、具有良好特点的INP测量，这些测量将被存档在公开可用的大学数据库中。该项目的测量结果将与现有的跨国北极研究界合作，提高对气溶胶性质的理解，而代表纽奥勒索德站点的INP参数化将极大地提高对冰形成过程的理解，而目前在气候模型中表现得很差。此外，这项研究活动直接与美国国家科学基金会的10个优先研究领域之一“航行新北极”相一致。这一奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

_____________________________________________________________________________________________________________________________The Arctic is warming rapidly – faster than the rest of the world. A number of processes have been proposed for this so-called Arctic polar amplification. While sea ice is known to play an important role on reflecting solar radiation and altering the Earth’s surface temperature, the roles of other processes are difficult to quantify. Especially, contributions from atmospheric mechanisms associated with ice-nucleating particles (INP; a few in a million aerosol particles below -20 °C) and ice-involved clouds remain uncertain in the Arctic. This project aims to fill the gap by investigating the sources (natural/manmade), atmospheric abundance/budget, chemical composition and physical properties of INPs in the Atlantic sector of the Arctic. Moreover, the large measurement uncertainties in number concentrations, chemical composition and sources of INPs are problematic for modeling real-life phenomena. This research targets minimizing the measurement uncertainties and addresses this critical deficiency through a series of studies that involve direct collection of ice-nucleating particles and their residuals. To characterize Arctic ice-nucleating particles, a novel portable ice nucleation experiment chamber and a cold stage-supported droplet freezing assay will be used to obtain freezing temperature spectra of airborne particle samples. A new inertial ice particle separation technique will be used to collect ice crystal residuals relevant to the Arctic ice-involved clouds. The subsequent offline microspectroscopic characterization of ice crystal residuals and ambient aerosol particles will reveal the relative importance of aerosol physicochemical properties to particle size in ice nucleation. Ultimately, the measurements of INPs and ice crystal residuals from this research will be parameterized and translated to describe the time-resolved freezing ability of the particles as a function of temperature, their composition, water activity parameters and other physicochemical properties. Finally, an integration of research and education is the most important target of this project. This project will involve two graduate and several undergraduate students in research, curriculum development and outreach, as these are learning experiences that can aid in their professional development. This project will also develop hands-on curricular modules integrated with the proposed research to teach environmental and climate science to the general public, promote college courses and train future scientists.Currently, there is a critical deficiency in Arctic field data regarding the abundance and composition of atmospheric ice-nucleating particles at temperatures above -15 °C. This project will fill this gap by experimentally elucidating abundance and physicochemical properties of ice-nucleating particles. State-of-the-art representations of high-temperature INPs from the Atlantic sector of the Arctic will advance the atmospheric modeling community’s knowledge of the ice nucleation processes and its formulation in the Earth’s energy balance. The project also aims to provide robust and well-characterized INP measurements that will be archived in the publicly available university database. The measurements from this project, in collaboration with the existing transnational Arctic research community, will improve the understanding of the nature of aerosols, and the INP parameterizations representative of the Ny-Ålesund site will dramatically improve the understanding of ice formation processes that are currently very poorly represented in climate models. In addition, this research activity directly aligns with one of the NSF’s 10 priority research areas, “Navigating the New Arctic”.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.