Collaborative Research: CHemistry in the Arctic-Clouds, Halogens, and Aerosols (CHACHA)

该项目旨在提高对大气化学的理解，在快速变化的北极背景下，大气化学会影响臭氧、颗粒物和云的化学成分。大气将污染物转化为可溶于水的产物，这些产物通过降水（雨或雪）或沉积在地球表面而被清除。这种污染的化学转化是通过被称为氧化的阳光驱动的（光化学）过程发生的。关于这些大气过程的大部分已知信息来自于在北极沿海环境的表面进行的测量。CHACHA小组计划使用两架仪器飞机在楚科奇海、波弗特海和阿拉斯加北坡地区进行空中测量。他们计划瞄准快速变化的特征——海冰“引线”（海冰覆盖海域的开放水域）的上下风向，以及燃烧衍生污染物来源的下风向。研究人员还将利用收集到的数据开发大气模型，这些模型将公开供更广泛的科学界使用。该团队由美国六所大学（阿拉斯加州、印第安纳州、密歇根州、宾夕法尼亚州和纽约州）的研究人员组成，并将指导一群不同的学生和博士后学者。研究人员还将参与几项额外的教育和推广活动，包括“飞机开放日”和在AK Utqiaġvik举行的为期三天的年度科学博览会。总的来说，这个项目将使美国能够更好地了解北极的快速变化如何影响大气的化学成分，并将所学到的知识转化为其他地区-包括世界海洋上方的大气和地球上层大气。此外，该项目由北极自然科学和大气化学项目共同资助。该项目将提高对大气中气体、气溶胶和云水相中的卤素化学的理解，重点关注北极海冰损失和化石燃料开采对化学的影响。CHACHA小组计划在卤素化学最活跃的北极春季进行为期八周的观测，使用两架飞机：怀俄明大学的King Air和普渡大学大气研究机载实验室（ALAR）。飞机将对上游和下游的铅（海冰断裂）、积雪覆盖的苔原和阿拉斯加油田北坡的顺风进行补充采样。采样将发生在不同的高度，从近地表穿过边界层进入自由对流层。该团队将优先测量各种温室气体（包括O3、CO2、CH4、H2O）、活性微量气体（包括NO2、SO2、N2O5、HO2NO2、含溴和含氯气体）、气溶胶大小分布和组成、云残留颗粒组成、云粒径分布以及大气数据。这些观测结果将部分使用0-D和1-D光化学模型以及云包模型进行解释，以评估和推进对北极大气卤素化学的多相反应和垂直和水平传播的理解。该数据集将提高对快速变化的北极对卤素化学和大气成分影响的理解，并提供可通过模型在全球应用的卤素化学基础知识。该团队将指导学生、博士后，并开展一系列独特的推广和教育活动。该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。

This project aims to improve understanding of atmospheric chemistry that impacts ozone, particulate matter, and cloud chemical composition in the context of a rapidly changing Arctic. The atmosphere converts pollutants by processing them into water-soluble products that are removed through precipitation (rain or snow) or by deposition onto Earth’s surface. This chemical conversion of pollution happens through a sunlight-driven (photochemical) process known as oxidation. Most of what is known about these atmospheric processes comes from measurements made at the surface in Arctic coastal environments. The CHACHA team plans to use two instrumented aircraft to conduct airborne measurements around the Chukchi Sea, the Beaufort Sea, and the Alaska North Slope region. They plan to target features that are rapidly changing - above and downwind of sea ice "leads" (areas of open water in otherwise sea-ice-covered ocean regions), and downwind of sources of combustion-derived pollutants. Researchers will also use collected data to develop atmospheric models that will be openly available for use by the broader scientific community. The team is composed of researchers at six United States universities (in Alaska, Indiana, Michigan, Pennsylvania, and New York) and will mentor a diverse group of students and postdoctoral scholars. Researchers will also engage in several additional education and outreach activities, including an “aircraft open house” and an annual three-day Science Fair in Utqiaġvik, AK. Overall, this project will enable the United States to better understand how rapid change in the Arctic impacts the chemical composition of the atmosphere and to translate what was learned to other regions - including the atmosphere above the world's oceans and in Earth's upper atmosphere. In addition, this project is co-funded by the Arctic Natural Sciences and Atmospheric Chemistry programs.This project will improve understanding of atmospheric halogen chemistry in the gas, aerosol, and cloud water phases, with a focus on how that chemistry is impacted by Arctic sea ice loss and fossil fuel extraction. The CHACHA team plans to conduct eight weeks of observations during the Arctic spring, when halogen chemistry is most active, using two aircraft: the University of Wyoming King Air and the Purdue University Airborne Laboratory for Atmospheric Research (ALAR). Aircraft will conduct complementary sampling upwind and downwind of leads (sea ice fractures), over snow-covered tundra, and downwind of the North Slope of Alaska oilfields. Sampling will occur at various altitudes from the near-surface through the boundary layer and into the free troposphere. The team will prioritize measurement of various greenhouse gases (including O3, CO2, CH4, H2O), reactive trace gases (including NO2, SO2, N2O5, HO2NO2, bromine- and chlorine-containing gases), aerosol size distributions and composition, cloud residual particle composition, and cloud particle size distributions, as well as atmospheric data. These observations will be interpreted in part using 0-D and 1-D photochemical models and a cloud parcel model, to evaluate and advance understanding of multi-phase reactions and the vertical and horizontal propagation of atmospheric halogen chemistry in the Arctic. This dataset will improve understanding of the impact of the rapidly changing Arctic on halogen chemistry and atmospheric composition, as well as to provide fundamental knowledge of halogen chemistry that can be applied globally through models. The team will mentor students, postdocs, and conduct an array of unique outreach and educational activities.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.