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，在北极快速变化的背景下影响臭氧，颗粒物和云的化学成分。大气将污染物转化为水溶性产品，这些产品通过降水（雨或雪）或沉积到地球表面而被去除。这种污染的化学转化是通过阳光驱动的（光化学）过程发生的，称为氧化。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表面进行的测量。CHACHA小组计划使用两架装有仪器的飞机在楚科奇海、博福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”（否则海冰覆盖的海洋区域的开放水域）的上方和顺风，以及燃烧衍生污染物来源的顺风。研究人员还将利用收集到的数据开发大气模型，供更广泛的科学界公开使用。该小组由美国六所大学（阿拉斯加、印第安纳州、密歇根、宾夕法尼亚和纽约）的研究人员组成，将指导一批不同的学生和博士后学者。研究人员还将参与一些额外的教育和推广活动，包括“飞机开放日”和在AK州Utqiagivik举行的为期三天的年度科学博览会。总的来说，该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，并将所学到的知识应用于其他地区，包括世界海洋上方的大气和地球的高层大气。此外，该项目由北极自然科学和大气化学项目共同资助。该项目将提高对气体，气溶胶和云水相大气卤素化学的理解，重点关注北极海冰损失和化石燃料开采对化学的影响。CHACHA团队计划在北极春季进行为期八周的观测，当时卤素化学最活跃，使用两架飞机：怀俄明州国王航空大学和普渡大学空中大气研究实验室（ALAR）。飞机将进行补充采样的上风和下风的线索（海冰裂缝），超过积雪覆盖的苔原，和顺风的北坡阿拉斯加油田。采样将在从近地表通过边界层进入自由对流层的不同高度进行。该团队将优先测量各种温室气体（包括O3，CO2，CH 4，H2O），反应性痕量气体（包括NO2，SO2，N2 O 5，HO 2NO 2，含溴和氯的气体），气溶胶尺寸分布和组成，云残余颗粒组成和云颗粒尺寸分布以及大气数据。这些观测结果将使用0-D和1-D光化学模型和云块模型进行部分解释，以评估和促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的影响的理解，并提供可通过模型在全球应用的卤素化学的基础知识。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。

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.