We have analyzed TROPOspheric Monitoring Instrument (TROPOMI) carbon monoxide (CO) data acquired between November 2017 and March 2019 with respect to other satellite (MOPITT, Measurement Of Pollution In The Troposphere) and airborne (ATom, Atmospheric Tomography mission) datasets to better understand TROPOMI's contribution to the global tropospheric CO record (2000 to present). MOPITT and TROPOMI are two of only a few satellite instruments to ever derive CO from solar-reflected radiances. Therefore, it is particularly important to understand how these two datasets compare. Our results indicate that TROPOMI CO retrievals over land show excellent agreement with respect to MOPITT: relative biases and their SD (i.e., accuracy and precision) are on average $-\mathrm{3.73}\mathrm{\%}\pm \mathrm{11.51}\mathrm{\%}$, $-\mathrm{2.24}\mathrm{\%}\pm \mathrm{12.38}\mathrm{\%}$, and $-\mathrm{3.22}\mathrm{\%}\pm \mathrm{11.13}\mathrm{\%}$ compared to the MOPITT TIR (thermal infrared), NIR (near infrared), and TIR + NIR (multispectral) products, respectively. TROPOMI and MOPITT data also show good agreement in terms of temporal and spatial patterns. Despite depending on solar-reflected radiances for its measurements, TROPOMI can also retrieve CO over bodies of water if clouds are present by approximating partial columns under cloud tops using scaled, model-based reference CO profiles. We quantify the bias of TROPOMI total column retrievals over bodies of water with respect to colocated in situ ATom CO profiles after smoothing the latter with the TROPOMI column averaging kernels (AKs), which account for signal attenuation under clouds (relative bias and its SD $=\mathrm{3.25}\mathrm{\%}\pm \mathrm{11.46}$ %). In addition, we quantify e_null (the null-space error), which accounts for differences between the shape of the TROPOMI reference profile and that of the ATom true profile ($e_{\text{null}}=\mathrm{2.16}\mathrm{\%}\pm \mathrm{2.23}$ %). For comparisons of TROPOMI and MOPITT retrievals over open water we compare TROPOMI total CO columns to their colocated MOPITT TIR counterparts. Relative bias and its SD are 2.98 %±15.71 % on average. We investigate the impact of discrepancies between the a priori and reference CO profiles (used by MOPITT and TROPOMI, respectively) on CO retrieval biases by applying a null-space adjustment (based on the MOPITT a priori) to the TROPOMI total column values. The effect of this adjustment on MOPITT and TROPOMI biases is minor, typically 1–2 percentage points.

中文翻译：

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TROPOMI CO测量1.5年：与MOPITT和ATom的比较

我们已经分析了2017年11月至2019年3月之间获取的对流层大气监测仪（TROPOMI）一氧化碳（CO）数据，以了解其他卫星（MOPITT，对流层污染测量）和机载（ATom，大气层析成像任务）数据集，以更好地理解TROPOMI对全球对流层CO记录的贡献（2000年至今）。MOPITT和TROPOMI是从太阳反射的辐射中提取CO的仅有的几种卫星仪器中的两个。因此，了解这两个数据集如何进行比较尤为重要。我们的结果表明，TROPOMI CO在陆地上的取回与MOPITT表现出极好的一致性：相对偏差及其SD（即准确度和精确度）是平均水平$--\mathrm{3.73}\mathrm{％}\pm \mathrm{11.51}\mathrm{％}$， $--\mathrm{2.24}\mathrm{％}\pm \mathrm{12.38}\mathrm{％}$和 $--\mathrm{3.22}\mathrm{％}\pm \mathrm{11.13}\mathrm{％}$与MOPITT TIR（热红外），NIR（近红外）和TIR  +  NIR（多光谱）产品相比。TROPOMI和MOPITT数据在时间和空间模式方面也显示出良好的一致性。尽管要依靠太阳反射的辐射进行测量，但是如果存在云，则TROPOMI还可以通过使用缩放的，基于模型的参考CO轮廓来近似云顶下的部分圆柱，从而在水体上获取CO。我们使用TROPOMI列平均核（AKs）平滑后，量化了相对于共处原位ATom CO轮廓在水体上TROPOMI总色谱柱取回的偏差，这可解释云下的信号衰减（相对偏差及其SD $=\mathrm{3.25}\mathrm{％}\pm \mathrm{11.46}$ ％）。此外，我们量化了e _null （零空间误差），它解释了TROPOMI参考轮廓和ATom true轮廓的形状之间的差异（${Ë}_{\text{空值}}=\mathrm{2.16}\mathrm{％}\pm \mathrm{2.23}$ ％）。为了比较TROPOMI和MOPITT在开放水域上的取水量，我们将TROPOMI总CO色谱柱与其共置的MOPITT TIR对应物进行了比较。相对偏差及其标准偏差平均为 2.98％±15.71  ％。我们通过对TROPOMI总列值应用零空间调整（基于MOPITT a先验）来研究先验和参考CO轮廓（分别由MOPITT和TROPOMI使用）之间的差异对CO检索偏差的影响。这种调整对MOPITT和TROPOMI偏差的影响很小，通常为1-2个百分点。