A Monte Carlo study of upper tropospheric reactive nitrogen during the Pacific Exploratory Mission in the Western Pacific Ocean (PEM‐West B)
A Monte Carlo study of upper tropospheric reactive nitrogen during the Pacific Exploratory Mission in the Western Pacific Ocean (PEM‐West B)
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西太平洋太平洋探索任务期间对流层上层活性氮的蒙特卡罗研究（PEM-West B）
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发表时间：
1997
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通讯作者：
Y. Kondo
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作者：
A. Thompson;H. Singh;R. Stewart;T. Kucsera;Y. Kondo
本文分析了1994年3月西太平洋探测使命（PEM-西B）资料的一个子集，用来代表对流层上部（UT）中纬度条件，以回答下列问题：（1）PEM-西B期间在该区域测得的总活性氮（NOy）是否存在短缺？(2)如果是这样，那么像HCN或其他活性氮物质这样的干扰成分可能有哪些贡献？对于问题1，我们的分析表明，UT中测得的总活性氮的87%由NOx + HNO 3 + PAN构成（类似于Kondo等人[本期（a，B）]、塔尔博特等人[本期]和Singh等人[1997 a，B]）。对于问题2，我们发现小于20 pptv（<平均NOy的5%）可能是HCN。一个一维模型，模拟平均混合比的PEM西B数据与蒙特卡洛方法来探索其他候选人的未测氮物种和NOy分区。使用具有不同速率系数的标准气相反应[Thompson和Stewart，1991; Stewart和Thompson，1996]，发现平均NOx + HNO 3 + PAN = 399 pptv（观察到的平均值等于432±97 pptv）。总活性氮（HNO 1 = NOx + HNO 3 + PAN + HNO 4 + CH 3 O2 NO2+硝酸烷基酯+C2 H5 O2 NO2）的更完整的存量为494±91 pptv，其中19%由HNO 4 + CH 3 O2 NO2+硝酸烷基酯组成。因此，无论是否存在未测量形式的活性氮，在PEM西B期间在中纬度UT测量的总活性氮都在测量不确定度内。最大的动力学不确定性是HNO 4、PAN和CH 3 O2 NO2的热膨胀损失（Stewart和Thompson [1996]的方法为120-150%）。尽管如此，与PEM-West B数据的比较表明小组推荐的动力学表达式[Demore等人，1994年]可以解释活性氮的观测，而不调用极端率或异质过程。总之，未测得的活性氮物种的大浓度并不普遍，在中纬度UT PEM西B采样，虽然观察到的短缺（13%）可以解释为硝酸+烷基硝酸盐+CH 3 O2 NO2。理论和观测之间的一致性也可能反映了测量活性氮的仪器能力的提高。
A subset of Pacific Exploratory Mission in the Western Pacific Ocean (PEM-West B) data (northwestern Pacific, March 1994), selected to represent upper troposphere (UT) midlatitude conditions, is analyzed to answer the following questions: (1) Is there a shortfall in total reactive nitrogen (NOy) as measured during PEM-West B in this region? (2) If so, what are the likely contributions of interfering constituents like HCN or of other reactive nitrogen species? For question 1 our analyses show that 87% of total reactive nitrogen measured in the UT is accounted for by NOx + HNO3 + PAN (similar to Kondo et al. [this issue (a, b)], Talbot et al. [this issue], and Singh et al. [1997a, b]). For question 2 we find that less than 20 pptv (<5% of mean NOy) is possibly HCN. A one-dimensional model that simulates mean mixing ratios of this PEM-West B data is used with a Monte Carlo approach to explore other candidates for unmeasured nitrogen species and NOy partitioning. Using standard gas-phase reactions with varying rate coefficients [Thompson and Stewart, 1991; Stewart and Thompson, 1996], it is found, on average, that NOx + HNO3 + PAN = 399 pptv (observed mean equal to 432±97 pptv). A more complete inventory for total reactive nitrogen (Σ NOi = NOx + HNO3 + PAN + HNO4 + CH3O2NO2 + alkyl nitrates + C2H5O2NO2) is 494±91 pptv, with 19% consisting of HNO4 + CH3O2NO2 + alkyl nitrates. Thus, whether unmeasured forms of reactive nitrogen are present or not, total reactive nitrogen as measured at midlatitude UT during PEM-West B is accounted for within the measurement uncertainty. The greatest kinetics uncertainties are in thermolytic losses for HNO4, PAN, and CH3O2NO2 (120–150% by the method of Stewart and Thompson [1996]). Nonetheless, comparison with PEM-West B data shows that panel-recommended kinetics expressions [Demore et al., 1994] can explain reactive nitrogen observations without invoking extreme rates or heterogeneous processes. In summary, large concentrations of unmeasured reactive nitrogen species were not prevalent during midlatitude UT PEM-West B sampling although the observed shortfall (13%) can be explained by HNO4 + alkyl nitrates + CH3O2NO2. Agreement between theory and observations may also reflect improved instrument capabilities for measuring reactive nitrogen.