Methane (CH) is the second-largest greenhouse gas contributing to global warming, surpassed only by CO, has a large difference in its vertical concentration distribution, and closely affects the global environment and climate change. The variations in the vertical concentrations of CH need to be monitored. Ground-based infrared hyperspectrometers can measure the fine variations of the CH concentrations in the vertical distribution within the planetary boundary layer (PBL). However, different detection channels are easily affected by instrumental noise and other environmental factors, leading to differences in the channel spectral characteristics and thereby affecting the accuracy of the CH profile retrieval. In this study, an information-weighted channel selection method is proposed for the CH profile retrieval using the Atmospheric Sounder Spectrometer by Infrared Spectral Technology (ASSIST) to address the differences in the channel characteristics from the different interference factors. This method leverages the information content of CH and its environmental interference factors in each channel to derive the weighting factors, and a comprehensive weighting approach is subsequently applied to ascertain the effective information content of CH. The method then establishes the threshold for the effective CH information content, considering the influence of noise, to select the optimal channels. We employ this method in our study, and 22 channels are selected as the optimal channels for the CH profile retrieval. We also evaluate the retrieval capability of the CH profile and the anti-interference ability of the selected channels using simulated spectra under clear-sky conditions. When retrieving the CH profile using the 1200–1390 cm band (394 channels in total), the CH profile is mainly affected by temperature, water vapor, aerosol optical depth (AOD) and NO. In addition, the mean absolute error (MAE) and the root mean square error (RMSE) for the CH profile retrieval using the selected channels are substantially reduced.

中文翻译：

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使用红外光谱技术的大气探测光谱仪进行 CH4 剖面检索的通道选择方法


甲烷（CH）是仅次于CO的第二大温室气体，其垂直浓度分布差异较大，密切影响全球环境和气候变化。需要监测 CH 垂直浓度的变化。地基红外高光谱仪可以测量行星边界层（PBL）内垂直分布的CH浓度的细微变化。然而不同的探测通道容易受到仪器噪声等环境因素的影响，导致通道光谱特性存在差异，从而影响CH剖面反演的准确性。在本研究中，提出了一种利用红外光谱技术（ASSIST）大气探测光谱仪进行CH剖面反演的信息加权信道选择方法，以解决不同干扰因素导致的信道特性差异。该方法利用CH的信息内容及其在每个信道中的环境干扰因素来推导加权因子，然后采用综合加权方法来确定CH的有效信息内容。该方法然后建立有效CH信息内容的阈值，考虑噪声的影响，以选择最佳信道。我们在研究中采用了这种方法，并选择 22 个通道作为 CH 剖面检索的最佳通道。我们还使用晴空条件下的模拟光谱来评估CH剖面的反演能力和所选通道的抗干扰能力。 使用1200~1390 cm波段（共394个通道）反演CH剖面时，CH剖面主要受温度、水蒸气、气溶胶光学深度（AOD）和NO的影响。此外，使用所选通道进行 CH 剖面检索的平均绝对误差 (MAE) 和均方根误差 (RMSE) 显着降低。