Abstract. Atmospheric radiative transfer models are extensively used in Earth observation to simulate radiative processes occurring in the atmosphere and to provide both upwelling and downwelling synthetic brightness temperatures for ground-based, airborne, and satellite radiometric sensors. For a meaningful comparison between simulated and observed radiances, it is crucial to characterize the uncertainty in such models. The purpose of this work is to quantify the uncertainty in radiative transfer models due to uncertainty in the associated spectroscopic parameters and to compute simulated brightness temperature uncertainties for millimeter- and submillimeter-wave channels of downward-looking satellite radiometric sensors (MicroWave Imager, MWI; Ice Cloud Imager, ICI; MicroWave Sounder, MWS; and Advanced Technology Microwave Sounder, ATMS) as well as upward-looking airborne radiometers (International Submillimetre Airborne Radiometer, ISMAR, and Microwave Airborne Radiometer Scanning System, MARSS). The approach adopted here is firstly to study the sensitivity of brightness temperature calculations to each spectroscopic parameter separately, then to identify the dominant parameters and investigate their uncertainty covariance, and finally to compute the total brightness temperature uncertainty due to the full uncertainty covariance matrix for the identified set of relevant spectroscopic parameters. The approach is applied to a recent version of the Millimeter-wave Propagation Model, taking into account water vapor, oxygen, and ozone spectroscopic parameters, though the approach is general and can be applied to any radiative transfer code. A set of 135 spectroscopic parameters were identified as dominant for the uncertainty in simulated brightness temperatures (26 for water vapor, 109 for oxygen, none for ozone). The uncertainty in simulated brightness temperatures is computed for six climatology conditions (ranging from sub-Arctic winter to tropical) and all instrument channels. Uncertainty is found to be up to few kelvins [K] in the millimeter-wave range, whereas it is considerably lower in the submillimeter-wave range (less than 1 K).

中文翻译：

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由于对厘米波至亚毫米波范围内的大气气体光谱参数的敏感性，模拟亮温存在不确定性


摘要。大气辐射传输模型广泛用于地球观测，以模拟大气中发生的辐射过程，并为地面、机载和卫星辐射传感器提供上升流和下降流合成亮度温度。为了对模拟和观测的辐射进行有意义的比较，表征此类模型中的不确定性至关重要。这项工作的目的是量化由于相关光谱参数的不确定性而导致的辐射传输模型的不确定性，并计算下视卫星辐射传感器（MicroWave Imager，MWI；冰云成像仪，ICI；微波探测仪，MWS；先进技术微波探测仪，ATMS）以及上视机载辐射计（国际亚毫米机载辐射计，ISMAR，和微波机载辐射计扫描系统，MARSS）。这里采用的方法是首先分别研究亮温计算对每个光谱参数的敏感性，然后识别主导参数并研究其不确定性协方差，最后计算由于全不确定性协方差矩阵而产生的总亮温不确定性。确定了一组相关的光谱参数。该方法应用于最新版本的毫米波传播模型，考虑了水蒸气、氧气和臭氧光谱参数，尽管该方法是通用的并且可以应用于任何辐射传输代码。 一组 135 个光谱参数被确定为模拟亮度温度不确定性的主要参数（26 个用于水蒸气，109 个用于氧气，没有一个用于臭氧）。模拟亮度温度的不确定性是针对六种气候条件（从亚北极冬季到热带）和所有仪器通道计算的。研究发现，毫米波范围内的不确定性高达几个开尔文 [K]，而亚毫米波范围内的不确定性要低得多（小于 1 K）。