Abstract. We present the first global glyoxal (CHOCHO) tropospheric column product derived from the TROPOspheric Monitoring Instrument (TROPOMI) on board of the Sentinel-5 Precursor satellite. Atmospheric glyoxal results from the oxidation of other non-methane volatile organic compounds (NMVOCs) and from direct emissions caused by combustion processes. Therefore, this product is a useful indicator of VOC emissions. It is generated with an improved version of the BIRA-IASB scientific retrieval algorithm relying on the Differential Optical Absorption Spectroscopy (DOAS) approach. Among the algorithmic updates, the DOAS fit now includes corrections to mitigate the impact of spectral misfits caused by scene brightness inhomogeneity and strong NO₂ absorption. The product comes along with a full error characterization, which allows providing random and systematic error estimates for every observation. Systematic errors are typically in the range of 1–3 × 10¹⁴ molec/cm² (~30–70 % in emission regimes). Random errors are larger (> 6 × 10¹⁴ molec/cm²) but can be reduced by averaging observations in space and/or time. Benefiting from a high signal-to-noise ratio and a large number of small-size observations, TROPOMI provides glyoxal tropospheric column fields with an unprecedented level of details. Using the same retrieval algorithmic baseline, glyoxal column data sets are also generated from the Ozone Monitoring Instrument (OMI) on Aura and from the Global Ozone Monitoring Experiment-2 (GOME-2) on board of Metop-A and Metop-B. Those four data sets are intercompared over large-scale regions worldwide and show a high level of consistency. The satellite glyoxal columns are also compared to glyoxal columns retrieved from ground-based Multi-Axis (MAX-) DOAS instruments at nine stations in Asia and Europe. In general, the satellite and MAX-DOAS instruments provide consistent glyoxal columns both in terms of absolute values and variability. Correlation coefficients between TROPOMI and MAX-DOAS glyoxal columns range between 0.61 and 0.87. The correlation is only poorer at one mid-latitude station, where satellite data appears low biased during wintertime. The mean absolute glyoxal columns from satellite and MAX-DOAS generally agree well for low/moderate columns with differences less than 1 × 10¹⁴ molec/cm². A larger bias is identified at two sites where the MAX-DOAS columns are very large. Despite this systematic bias, the consistency of the satellite and MAX-DOAS glyoxal seasonal variability is excellent.

中文翻译：

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来自 TROPOMI 的乙二醛对流层柱反演、多卫星比对和地面验证

摘要。我们展示了来自 Sentinel-5 Precursor 卫星上的对流层监测仪器 (TROPOMI) 的第一个全球乙二醛 (CHOCHO) 对流层柱产品。大气中的乙二醛来自其他非甲烷挥发性有机化合物 (NMVOC) 的氧化以及燃烧过程引起的直接排放。因此，该产品是VOC排放的有用指标。它是使用基于差分光吸收光谱 (DOAS) 方法的 BIRA-IASB 科学检索算法的改进版本生成的。在算法更新中，DOAS 拟合现在包括修正，以减轻由场景亮度不均匀和强 NO ₂引起的光谱失配的影响吸收。该产品带有完整的误差特征，允许为每次观察提供随机和系统的误差估计。系统误差通常在 1–3 × 10 ¹⁴  molec/cm ²范围内（在排放范围内约为 30–70 %）。随机误差较大（> 6 × 10 ¹⁴  molec/cm ²) 但可以通过对空间和/或时间中的观察进行平均来减少。得益于高信噪比和大量小尺寸观测，TROPOMI 提供了具有前所未有的细节水平的乙二醛对流层柱场。使用相同的检索算法基线，乙二醛列数据集也从 Aura 上的臭氧监测仪器 (OMI) 和 Metop-A 和 Metop-B 上的全球臭氧监测实验 2 (GOME-2) 生成。这四个数据集在全球范围内的大范围区域进行了比较，并显示出高度的一致性。还将卫星乙二醛柱与从亚洲和欧洲九个站点的地面多轴 (MAX-) DOAS 仪器中提取的乙二醛柱进行比较。一般来说，卫星和 MAX-DOAS 仪器在绝对值和变异性方面提供一致的乙二醛柱。TROPOMI 和 MAX-DOAS 乙二醛柱之间的相关系数介于 0.61 和 0.87 之间。仅在一个中纬度站的相关性较差，那里的卫星数据在冬季出现低偏差。来自卫星和 MAX-DOAS 的平均绝对乙二醛柱对于低/中柱普遍一致，差异小于 1 × 10¹⁴ 摩尔/厘米²。在 MAX-DOAS 列非常大的两个站点上发现了更大的偏差。尽管存在这种系统偏差，但卫星和 MAX-DOAS 乙二醛季节性变化的一致性非常好。