A Global Survey of Helium in the Troposphere: Advancing the Application of Helium as a Tracer of Natural Gas Usage and Stratosphere-Troposphere Exchange

该项目旨在根据先前开发的测量技术对惰性气体氦建筑进行全球调查。氦是一种难以测量的气体，可以用作大气示踪剂，这意味着新的测量可以帮助我们更好地了解广泛的过程，包括南北半球之间的大规模大气传输，以及释放氦的小规模过程，如天然气开采。该项目将收集的独特的氦测量将为各种大气传输现象提供新的见解，并将增加我们对氦和可能的其他惰性气体的来源和可变性的了解。早期职业科学家和一名研究生将在整个项目过程中得到支持，收集到的数据将与更广泛的科学界共享。在该项目期间，将通过一种新的质谱测量技术，通过使用双捕获系统和低温浓缩入口的新质谱学测量技术，测量气体氦(He)和氮(N2)(He/N2)之间的比率。在这项拟议的工作中提出了四个研究问题：(1)最丰富的氦同位素4He的年际变化是什么？(2)氦/氮的空间梯度是什么，特别是在南北半球之间？(3)氦/氮的季节变化有多大？(4)通过研究高频氦的变化可以得到什么？这项拟议的工作将使用三个测量来源：从以前的工作中收集的历史烧瓶样本，显示出过去50年来大气氦水平的上升趋势；持续收集的烧瓶样本，由斯克里普斯氧气计划定期收集，斯克里普斯氧气计划是一个分布在太平洋各地的能够解析全球尺度信号的地面烧瓶站网络；以及在加利福尼亚州拉霍亚的斯克里普斯码头采集的准连续环境样本。该奖项反映了NSF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。

This project seeks to conduct a global survey of the noble gas helium building upon a previously developed measurement technique. Helium, which is a difficult gas to measure, can be used as an atmospheric tracer, meaning that new measurements could help us better understand a wide range of processes including large-scale atmospheric transport between the northern and southern hemispheres as well as small-scale processes that emit helium such natural gas extraction. The unique measurements of helium to be collected in this project will provide new insight into a variety of atmospheric transport phenomena and will increase our understanding of the sources and variability of helium and potentially other noble gases. Early career scientists and a graduate student will be supported throughout the course of this project, and the data collected will be shared with the wider scientific community.The new observations to be made during this project will be of the ratio between the gases helium (He) and nitrogen (N2) (He/N2) via a new mass spectrometric measurement technique using a dual-trapping system and cryo-enrichment inlets developed under a previous NSF-funded project. There are four research questions being asked in this proposed work: (1) what is the interannual variability of the most abundant helium isotope 4He?; (2) what are the He/N2 spatial gradients, particularly between the northern and southern hemispheres?; (3) what is the magnitude of seasonal He/N2 variations?; and (4) what can be learned by examining high frequency He variability? This proposed work will use three sources of measurement: historic flask samples collected from previous work that has demonstrated an increasing trend in atmospheric He levels over the last 50 years, the ongoing collection of flask samples collected routinely by the Scripps oxygen program, which is a network of 10 surface flask stations spread out around the Pacific Ocean capable of resolving global-scale signals, and quasi-continuous ambient samples taken at the Scripps Pier in La Jolla, California.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.