Abstract. We have developed in situ and flask sampling systems for airborne measurements of variations in the O₂/N₂ ratio at the part per million level. We have deployed these instruments on a series of aircraft campaigns to measure the distribution of atmospheric O₂ from 0–14 km and 87° N to 85° S throughout the seasonal cycle. The NCAR airborne oxygen instrument (AO2) uses a vacuum ultraviolet (VUV) absorption detector for O₂ and also includes an infrared CO₂ sensor. The VUV detector has a precision in 5 seconds of ±1.25 per meg (1σ) δ(O₂/N₂), but thermal fractionation and motion effects increase this to ±2.5–4.0 per meg when sampling ambient air in flight. The NCAR/Scripps airborne flask sampler (Medusa) collects 32 cryogenically dried air samples per flight under actively controlled flow and pressure conditions. For in situ or flask O₂ measurements, fractionation and surface effects can be important at the required high levels of relative precision. We describe our sampling and measurement techniques, and efforts to reduce potential biases. We also present a selection of observational results highlighting the individual and combined instrument performance. These include vertical profiles, O₂ : CO₂ correlations, and latitudinal cross sections reflecting the distinct influences of terrestrial photosynthesis, air-sea gas exchange, burning of various fuels, and stratospheric dynamics. When present, we have corrected the flask δ(O₂/N₂) measurements for fractionation during sampling or analysis, with the use of the concurrent δ(Ar/N₂) measurements. We have also corrected the in situ δ(O₂/N₂) measurements for inlet fractionation and humidity effects by comparison to the corrected flask values. A comparison of Ar/N₂-corrected Medusa flask δ(O₂/N₂) measurements to regional Scripps O₂ Network station observations shows no systematic biases over 10 recent campaigns (+0.2 ± 8.2 per meg, mean and standard deviation, n = 86). For AO2, after resolving sample drying and inlet fractionation biases previously on the order of 10–100 per meg, independent AO2 δ(O₂/N₂) measurements over 6 more recent campaigns differ from coincident Medusa flask measurements by −0.3 ± 7.2 per meg (mean and standard deviation, n = 1361), with campaign-specific means ranging from −5 to +5 per meg.

中文翻译：

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机载测量从地表到低空平流层以及极与极之间的氧气浓度

摘要。我们已经开发了就地和烧瓶采样系统，用于空中测量O ₂ / N ₂比值（百万分之一）的变化。我们在一系列飞机战役中部署了这些仪器，以测量整个季节周期中从0–14 km和从87°N到85°S的大气O ₂分布。NCAR机载氧气仪器（AO2）使用用于O ₂的真空紫外线（VUV）吸收检测器，还包括一个红外CO ₂传感器。VUV检测器在5秒内的精度为每兆（1σ）δ（O ₂ / N ₂每±1.25）），但在对飞行中的环境空气进行采样时，热分馏和运动效应会将其提高到每兆±2.5–4.0。NCAR / Scripps机载烧瓶采样器（Medusa）在主动控制的流量和压力条件下，每次飞行收集32个低温干燥的空气样本。对于原位或烧瓶O ₂测量，在要求的较高相对精度水平下，分馏和表面效果可能很重要。我们描述了我们的采样和测量技术，以及为减少潜在偏差所做的努力。我们还提供了一些观察结果，以突出单个和组合仪器的性能。这些包括垂直轮廓，O ₂  ：CO ₂相关性和纬度横截面反映了陆地光合作用，海气交换，各种燃料燃烧和平流层动力学的独特影响。当存在时，我们已使用并发δ（Ar / N ₂）测量值校正了烧瓶δ（O ₂ / N ₂）测量值在采样或分析过程中的分离度。通过与校正后的烧瓶值进行比较，我们还校正了入口分馏和湿度影响的原位δ（O ₂ / N ₂）测量值。Ar / N ₂校正的美杜莎烧瓶δ（O ₂ / N ₂）测量值与区域Scripps O _2的比较网络站的观测结果显示，在最近的10次运动中没有系统的偏差（每兆+0.2±8.2，均值和标准差，n = 86）。对于AO2，在解决样品干燥和入口分馏偏差先前约为10–100每兆克之后，最近6次运动中独立的AO2δ（O ₂ / N ₂）测量结果与同时进行的美杜莎烧瓶测量结果的差为-0.3±7.2梅格（均值和标准差，n = 1361），特定于战役的均值范围为每梅特-5至+5。