Observed NO/NO2 Ratios in the Upper Troposphere Imply Errors in NO‐NO2‐O3 Cycling Kinetics or an Unaccounted NOx Reservoir
Observed NO/NO2 Ratios in the Upper Troposphere Imply Errors in NO‐NO2‐O3 Cycling Kinetics or an Unaccounted NOx Reservoir
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DOI：
10.1029/2018gl077728
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发表时间：
2018-05
影响因子：
5.2
通讯作者：
R. Silvern;D. Jacob;K. Travis;T. Sherwen;M. Evans;R. Cohen;J. Laughner;S. Hall;K. Ullmann;J. Crounse;P. Wennberg;Je;Peischl;I. Pollack
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作者：
R. Silvern;D. Jacob;K. Travis;T. Sherwen;M. Evans;R. Cohen;J. Laughner;S. Hall;K. Ullmann;J. Crounse;P. Wennberg;Je;Peischl;I. Pollack
2013 年 8 月至 9 月 SEAC4RS 飞机在美国东南部上空进行的观测显示，对流层上层的 NO/NO2 浓度比约为喷气推进实验室 (JPL) 动力学数据计算出的光化学平衡值的一半。一种可能的解释是存在不稳定的氮氧化物储存物种（可能是有机物），在仪器中热分解为二氧化氮。 NO2 仪器可纠正已知不稳定 HNO4 和 CH3O2NO2 NOx 储层中的这种伪影。为了弥合测量和模拟 NO2 之间的差距，在 SEAC4RS 条件下，额外的未计算的不稳定 NOx 储存物种的平均浓度必须约为 40 ppt（相比之下，NOx 为 197 ppt）。另一种解释是 NO + O3 反应的低温速率常数存在误差（JPL 在 240 K 时的 1-σ 不确定性为 30%）和/或 NO2 光解的光谱数据（20% 1-σ 不确定性）。解决这一差异对于了解对流层氧化剂的全球预算和解释对流层 NO2 柱的卫星观测结果非常重要。
Observations from the SEAC4RS aircraft campaign over the southeast United States in August–September 2013 show NO/NO2 concentration ratios in the upper troposphere that are approximately half of photochemical equilibrium values computed from Jet Propulsion Laboratory (JPL) kinetic data. One possible explanation is the presence of labile NOx reservoir species, presumably organic, decomposing thermally to NO2 in the instrument. The NO2 instrument corrects for this artifact from known labile HNO4 and CH3O2NO2 NOx reservoirs. To bridge the gap between measured and simulated NO2, additional unaccounted labile NOx reservoir species would have to be present at a mean concentration of ~40 ppt for the SEAC4RS conditions (compared with 197 ppt for NOx). An alternative explanation is error in the low‐temperature rate constant for the NO + O3 reaction (30% 1‐σ uncertainty in JPL at 240 K) and/or in the spectroscopic data for NO2 photolysis (20% 1‐σ uncertainty). Resolving this discrepancy is important for understanding global budgets of tropospheric oxidants and for interpreting satellite observations of tropospheric NO2 columns.