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。对于这种所谓的北极极地放大，已经提出了一些过程。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着重要作用，但其他过程的作用难以量化。特别是，与冰成核粒子（INP;低于-20 °C的百万分之几的气溶胶粒子）和冰云相关的大气机制在北极的贡献仍然不确定。该项目旨在通过调查北极大西洋部分的国际非颗粒物的来源（自然/人为）、大气丰度/预算、化学组成和物理性质来填补差距。此外，在数浓度，化学成分和来源的INPs的大测量不确定性是建模现实生活中的现象的问题。这项研究的目标是最大限度地减少测量的不确定性，并通过一系列涉及直接收集冰成核颗粒及其残留物的研究来解决这一关键缺陷。为了表征北极冰成核颗粒，一种新型的便携式冰成核实验室和冷台支持的液滴冻结试验将被用来获得空气中颗粒样品的冻结温度谱。一种新的惯性冰粒分离技术将用于收集与北极冰云有关的冰晶残留物。随后的离线显微光谱表征的冰晶残留物和周围的气溶胶颗粒将揭示气溶胶的物理化学性质的相对重要性，在冰成核的颗粒大小。最终，本研究中INPs和冰晶残留物的测量结果将被参数化和翻译，以描述颗粒的时间分辨冻结能力，作为温度，其组成，水活度参数和其他物理化学性质的函数。最后，研究与教育的整合是本项目的最重要目标。该项目将涉及两名研究生和几名本科生的研究，课程开发和推广，因为这些都是学习经验，可以帮助他们的专业发展。该项目还将开发与拟议的研究相结合的实践课程模块，向公众教授环境和气候科学，促进大学课程和培训未来的科学家，目前，北极实地数据严重缺乏关于温度高于-15 °C时大气冰成核颗粒的丰度和组成的数据。该项目将通过实验阐明冰成核颗粒的丰度和物理化学性质来填补这一空白。来自北极大西洋部分的高温INPs的最先进的表示将推进大气模拟界对冰成核过程及其在地球能量平衡中的形成的认识。该项目还旨在提供稳健和特征良好的INP测量结果，这些测量结果将存档在公开的大学数据库中。与现有的跨国北极研究团体合作，该项目的测量结果将提高对气溶胶性质的理解，而代表Ny-此外，该研究活动直接与NSF的10个优先研究领域之一“导航新北极”保持一致。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.