Measurement of Atmospheric He/N2 (Helium to Nitrogen) Ratio as a Tracer of Stratospheric-Tropospheric Exchange

该项目支持开发新的仪器，以非常精确地测量大气中氦（He）与氮（N2）的浓度之比。对这一比率的测量将用于评估平流层（对流层上方的大气层）和对流层（最接近地球表面的大气层的最低部分）之间的大气成分交换。更好地了解平流层-对流层交换（STE）对于增加关于大气的一般知识和改进预测天气和气候的模式非常重要。新开发的仪器将用于：(1)测量斯克里普斯海洋研究所高压气瓶档案中记录的He/N2的长期趋势，该档案可追溯到20世纪70年代；(2)在La Jolla进行为期一年的He/N2实时测量，在那里预计与Santa Anna风事件相关的平流层影响；(3)测试新方法，以允许在烧瓶样品中测量He/N2比率。模拟研究将用于评估预期的平流层对He/N2比率的影响。该项目预计将首次提供He/N2比值的季节和天气变化估计。这一努力还将提高测量Ar/N2的能力，以限制海洋变暖。这项新技术将用于增进对平流层环流的了解及其对对流层化学的影响，并最终通过评估这些化合物的来源来更好地了解人类活动对大气的影响。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 supports the development of new instrumentation to measure very precisely the ratio of the concentration of helium (He) to nitrogen (N2) in the atmosphere. Measurements of this ratio will be used to evaluate the exchange of atmospheric constituents between the stratosphere (the layer of the atmosphere just above the troposphere) and the troposphere, the lowest portion of the atmosphere closest to the Earth's surface. Better understanding of stratospheric-tropospheric exchange (STE) is important for increasing general knowledge about the atmosphere and improving models that predict weather and climate.The newly developed instrumentation will be used to: (1) measure long-term trends in He/N2 as recorded in the Scripps Institute of Oceanography archive of high pressure gas cylinders of air that extends back to the 1970s; (2) conduct real-time measurements of He/N2 for a period spanning one year at La Jolla, where stratospheric influences are expected in association with Santa Anna wind events; and (3) test new methods to allow He/N2 ratios to be measured in flask samples. Modeling studies will be used to assess the expected stratospheric influences on the He/N2 ratio. This project is expected to provide the first estimates of seasonal and synoptic variations in the He/N2 ratio. This effort will also improve the ability of Ar/N2 measurements to serve as a constraint on ocean warming. The new technique will be used to advance the understanding of stratospheric circulation and the resulting implications for tropospheric chemistry, and ultimately, by assessing the sources of these compounds, to attain a better understanding of the effects of human activities on the atmosphere.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.