The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O₃ and CH₄ (O₃, CH₄, CO, H₂O, HCHO, H₂O₂, CH₃OOH, C₂H₆, higher alkanes, alkenes, aromatics, NO_x, HNO₃, HNO₄, peroxyacetyl nitrate, other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O₃ and CH₄ photochemical tendencies from this modeling data stream for ATom 1. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. In other words, accurate simulation of the least reactive 50 % of the troposphere is unimportant for global budgets. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find excellent agreement with the loss of O₃ and CH₄ but sharp disagreement with production of O₃. The models sharply underestimate O₃ production below 4 km in both Pacific and Atlantic basins, and this can be traced to lower NO_x levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation.

中文翻译：

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飞机测量定义的远程对流层的异质性和化学反应性

美国宇航局大气层析成像 (ATom) 任务基于美国宇航局 DC-8 飞机沿着客观规划的剖面横断面穿过太平洋和大西洋中部的原位测量，建立了气团的光化学气候学。在本文中，我们提出并分析了 10 秒（2 公里）的数据集，这些数据集对驱动 O ₃和 CH ₄ （O ₃、CH ₄、CO、H ₂ O , HCHO, H ₂ O ₂ , CH ₃ OOH, C ₂ H ₆ , 高级烷烃, 烯烃, 芳烃, NO _x , HNO ₃ , HNO ₄、过氧乙酰硝酸盐、其他有机硝酸盐），由来自 ATom 部署 1 到 4 的 146 494 个不同的空气包裹组成。六个模型根据ATom 1 的建模数据流计算了 O ₃和 CH ₄光化学趋势。我们发现 80 %–90总反应性的 % 位于前 50% 的地块中，25%–35% 位于前 10% 的地块中，支持之前的模型研究，即对流层化学是由一小部分空气驱动的。换句话说，对对流层反应最小的 50% 的准确模拟对于全球预算来说并不重要。令人惊讶的是，物种的概率密度和模型尺度（100 公里）上的平均反应性与 2 公里 ATom 数据仅略有不同，这表明对流层化学的大部分异质性可以用当前的全球化学模型捕获。将热带海洋上的原子反应活性与来自六个全球化学模型的气候统计数据进行比较，我们发现与 O ₃和 CH ₄的损失非常吻合，但与 O _{3 的}产生明显不同。这些模型严重低估了太平洋和大西洋盆地 4 公里以下的O ₃产量，这可以追溯到降低 NO _x比观察到的水平。将光化学反应性附加到化学物质的测量中，可以为模型评估提供更丰富但更受限制的指标集。