Abstract. We evaluate vertical profile retrievals of CO₂ from 0.02 cm⁻¹ resolution ground-based near-infrared solar absorption spectra with the GFIT2 algorithm, using improved spectroscopic linelists and line shapes. With these improvements, CO₂ profiles were obtained from sequential retrievals in five spectral windows with different vertical sensitivities. A sensitivity study using synthetic spectra shows that the leading source of uncertainty in the retrieved CO₂ profiles is the error in the a priori temperature profile, even with 3-hourly reanalysis a priori profiles. A 2 °C error in the temperature profile in the lower troposphere between 0.6 and 0.85 atm causes deviations in the retrieved CO₂ profiles that are larger than the typical vertical variations of CO₂. To distinguish the effect of errors in the a priori meteorology and trace gas concentration profiles from those in the instrument alignment and spectroscopic parameters, we retrieve CO₂ profiles from atmospheric spectra while using an a priori built from coincident AirCore, radiosonde, and surface in situ measurements at the Lamont, Oklahoma (USA) Total Carbon Column Observing Network station. In those cases, the deviations in retrieved CO₂ profiles are also larger than typical vertical variations of CO₂, suggesting that remaining errors in the forward model limit the accuracy of the retrieved profiles. Implementing a temperature retrieval or correction, and quantifying and modeling an imperfect instrument alignment, are critical to improve CO₂ profile retrievals. Without significant advances in modeling imperfect instrument alignment, and improvements in the accuracy of the temperature profile, the CO₂ profile retrieval with GFIT2 presents no clear advantage over scaling retrievals for the purpose of ascertaining the total column.

中文翻译：

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从地基近红外光谱中提取大气CO ₂垂直剖面

摘要。我们使用改进的光谱线列表和线形，使用GFIT2算法，从0.02 cm ^-1分辨率的地面近红外太阳吸收光谱评估了CO _2的垂直剖面检索。通过这些改进，从五个具有不同垂直灵敏度的光谱窗口中的顺序检索获得了CO ₂剖面。使用合成光谱进行的敏感性研究表明，即使先后进行了3小时的重新分析，先验温度曲线中的误差也是所获取的CO ₂曲线不确定性的主要来源。对流层下部温度曲线的2°C误差在0.6至0.85 atm之间会导致所获取的CO ₂发生偏差轮廓大于典型的CO ₂垂直变化。为了区分先验气象学和痕量气体浓度剖面中的误差与仪器校准和光谱参数中的误差影响，我们使用从空芯，探空仪和地面重合而来的先验来从大气光谱中检索CO ₂剖面在美国俄克拉荷马州拉蒙特市的总碳柱观测网络站进行测量。在那些情况下，所获得的CO ₂剖面的偏差也大于典型的CO ₂垂直变化，表明前向模型中的剩余错误会限制检索到的配置文件的准确性。实施温度检索或校正以及对不完善的仪器对准进行量化和建模，对于改善CO ₂剖面检索至关重要。如果在建模不完善的仪器对准方面没有重大进展，并且温度分布图的准确性没有提高，那么使用GFIT2进行CO ₂分布图检索就无法确定定标总色谱柱，而与按比例缩小检索值相比并没有明显优势。