The diurnal variability of atmospheric nitrogen oxides (NO and NO 2 ) above the Antarctic Plateau driven by atmospheric stability and snow emissions
The diurnal variability of atmospheric nitrogen oxides (NO and NO 2 ) above the Antarctic Plateau driven by atmospheric stability and snow emissions
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由大气稳定性和雪排放驱动的南极高原上空大气氮氧化物（NO 和 NO 2 ）的日变化
DOI：
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发表时间：
2012
期刊：
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通讯作者：
J. Savarino
中科院分区：
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作者：
M. Frey;N. Brough;P. Anderson;O. Traullé;M. King;A. Jones;E. Wolff;J. Savarino
抽象的。2009年12月10日至2010年1月28日，在东南极洲Dome C（75.1° S，123.3° E，3233 m）对大气氮氧化物（NO和NO2）进行了为期50天的观测。首次在东南极高原测得的1.0 m处NO和NO2的平均（±1σ）混合比分别为111（±89）pptv和98（±89）pptv。大气混合比平均相当于以前在南极观察到的，但相比之下，表现出强烈的日变化：当地中午附近的最小值和傍晚的最大值与对流边界层的发展和崩溃相吻合。的不对称的昼夜循环的NOx浓度和可能的任何其他化学示踪剂与光解表面源驱动的湍流扩散率和高度的大气边界层，与前者控制的垂直通量的大小和后者的体积的大小，其中雪排放被运输。特别是，从大气浓度梯度估算的2009年12月22日至2010年1月28日的平均（±1σ）NOx排放通量，为8.2（±7.4）× 10 12分子m −2 s −1属于迄今为止在极地地区测得的最大值，并解释了3-傍晚时分，当边界层变得非常浅时，混合比增加一倍。冰穹C可能并不代表整个东南极高原，但说明了在大气化学模型中需要准确描述雪上方的边界层。一个简单的硝酸盐光解模型在白天与观测到的平均日氮氧化物通量相匹配，但在夜间具有显着的低偏差。考虑到通量观测的总随机误差和雪中NO3 −浓度的变化以及NO2 −光解的潜在贡献所导致的模型不确定性，差异是显着的。这突出了在自然积雪中的光解氮氧化物源的参数化的不确定性，如硝酸盐光解的量子产率约束不佳。稳态分析的NO 2：NO的比例表明，过氧（HO 2 + RO 2）或其他自由基的浓度在边界层的圆顶C要么高于其他地方测量的极地地区或其他过程导致增强NO 2必须调用。这些结果证实了存在一个强氧化的树冠包围东南极高原在夏季。
Abstract. Atmospheric nitrogen oxides (NO and NO 2 ) were observed at Dome C, East Antarctica (75.1° S, 123.3° E, 3233 m), for a total of 50 days, from 10 December 2009 to 28 January 2010. Average (±1σ) mixing ratios at 1.0 m of NO and NO 2 , the latter measured for the first time on the East Antarctic Plateau, were 111 (±89) and 98 (±89) pptv, respectively. Atmospheric mixing ratios are on average comparable to those observed previously at South Pole, but in contrast show strong diurnal variability: a minimum around local noon and a maximum in the early evening coincide with the development and collapse of a convective boundary layer. The asymmetric diurnal cycle of NO x concentrations and likely any other chemical tracer with a photolytic surface source is driven by the turbulent diffusivity and height of the atmospheric boundary layer, with the former controlling the magnitude of the vertical flux and the latter the size of the volume into which snow emissions are transported. In particular, the average (±1σ) NO x emission flux from 22 December 2009 to 28 January 2010, estimated from atmospheric concentration gradients, was 8.2 (±7.4) × 10 12 molecule m −2 s −1 belongs to the largest values measured so far in the polar regions and explains the 3-fold increase in mixing ratios in the early evening when the boundary layer becomes very shallow. Dome C is likely not representative for the entire East Antarctic Plateau but illustrates the need of an accurate description of the boundary layer above snow in atmospheric chemistry models. A simple nitrate photolysis model matches the observed median diurnal NO x flux during the day but has significant low bias during the night. The difference is significant taking into account the total random error in flux observations and model uncertainties due to the variability of NO 3 − concentrations in snow and potential contributions from NO 2 − photolysis. This highlights uncertainties in the parameterization of the photolytic NO x source in natural snowpacks, such as the poorly constrained quantum yield of nitrate photolysis. A steady-state analysis of the NO 2 : NO ratios indicates that peroxy (HO 2 + RO 2 ) or other radical concentrations in the boundary layer of Dome C are either higher than measured elsewhere in the polar regions or other processes leading to enhanced NO 2 have to be invoked. These results confirm the existence of a strongly oxidising canopy enveloping the East Antarctic Plateau in summer.