An accurate determination of atmospheric transmittance relies greatly on the quality of both absorption line parameters and continuum absorption model. A line‐by‐line radiative transfer model has been used to determine the magnitude of the changes in atmospheric transmittance due to recent updates of HITRAN (HIgh‐resolution TRANsmission) line parameters and differences in water vapour continuum formulation. The radiative transfer calculations were carried out at two narrow near‐infrared carbon dioxide bands near 4,854 cm⁻¹ (2.06 μm) and 6,211 cm⁻¹ (1.61 μm), which are currently used by satellite‐based instruments for retrieval of atmospheric CO₂ concentrations. Transmittance calculations using line parameters from the last three HITRAN editions (2008, 2012 and 2016) show that HITRAN2016 is more similar to HITRAN2012 than HITRAN2008. However, differences of up to about 5% were obtained between transmittances computed using HITRAN2016 and HITRAN2012. Considering the fact that some groups still use HITRAN2012 in forward models for very high (sub percent) accuracy retrievals of CO₂ from satellite measurements, these differences are significant and should be accounted for in the uncertainty budget. Transmittances calculated using the semi‐empirical MT_CKD 2.5 (Mlawer–Tobin–Clough–Kneizys–Davies) and the laboratory‐measured CAVIAR (Continuum Absorption at Visible and Infrared Wavelengths and its Atmospheric Relevance) water vapour continuum models differ by up to about 5–6%. The impact of the continuum formulation adopted for near‐infrared transmittance calculations needs to be quantitatively assessed, most especially as the strength of the water vapour continuum in this spectral region is still contested.

中文翻译：

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用于遥感应用的近红外透射率计算对光谱信息最近变化的敏感性

大气透射率的准确确定在很大程度上取决于吸收线参数和连续吸收模型的质量。由于最近更新了HITRAN（高分辨率TRANsmission）线参数和水蒸气连续体配方的差异，使用了逐线辐射传递模型来确定大气透射率变化的幅度。辐射传递计算是在两个狭窄的近红外二氧化碳带（分别为4,854 cm ^-1（2.06μm）和6,211 cm ^-1（1.61μm ））附近进行的，目前基于卫星的仪器已将其用于大气CO _2的获取。浓度。使用最后三个HITRAN版本（2008、2012和2016）中的线参数进行的透射率计算显示，HITRAN2016与HITRAN2012的相似性高于HITRAN2008。但是，使用HITRAN2016和HITRAN2012计算的透射率之间的差异高达5％。考虑到以下事实，即某些小组仍在正模型中使用HITRAN2012进行非常高（低于百分比）的CO ₂准确度检索从卫星测量结果来看，这些差异非常明显，应在不确定性预算中予以考虑。使用半经验MT_CKD 2.5（Mlawer-Tobin-Clough-Kneizys-Davies）和实验室测量的CAVIAR（可见光和红外波长下的连续吸收及其大气相关性）计算的透光率相差最多约5– 6％。需要定量评估近红外透射率计算所采用的连续谱公式的影响，尤其是在该光谱区域中水蒸气连续谱的强度仍存在争议的情况下。