Quality Optimization Method for Ambient CO2 Inversion of High Resolution Fourier Transform Infrared Spectrum
TIAN Yuan1, SUN You-wen1*, XIE Pin-hua1，2, LIU Cheng2, LIU Wen-qing1，2, LIU Jian-guo1，2, LI Ang1, HU Ren-zhi1, WANG Wei1, ZENG Yi1
1. Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China 2. College of Environmental Optics & Technology, University of Science and Technology of China, Hefei 230031, China
Abstract：CO2 retrievals with high quality facilitate resolving the sources and sinks of CO2 are helpful in predicting the trend in climate change and understanding the global carbon cycle. Based on a nonlinear least squares spectral fitting algorithm, we investigate the optimization method for CO2 products derived from ground-based high resolution Fourier transform infrared spectra. The CO2 vertical column densities (VCDs) are converted into column-averaged dry air mole fraction XCO2 by using the fitted O2 VCDs, and thus the system errors (e. g. pointing errors, ILS errors, zero-level offset) are corrected greatly. The virtual daily variation which is related to air mass factor is corrected with an empirical model. The spectra screening rule proposed in this paper can greatly improve the XCO2 quality. The CO2 retrievals before and after the optimized method are compared using a typical CO2 daily time series. After using the optimized method, the fitting error is reduced by 60%, and the two-hours-averaged precision is ~0.071% (equals to ~0.28 ppm), which is perfectly in line with the TCCON (the total carbon column observing network) threshold, i. e., less than 0.1%.
田 园1，孙友文1*，谢品华1，2，刘 诚2，刘文清1，2，刘建国1，2，李 昂1，胡仁志1，王 薇1，曾 议1 . 高分辨率傅里叶变换红外光谱反演环境大气中CO2浓度的质量优化方法 [J]. 光谱学与光谱分析, 2017, 37(01): 48-53.
TIAN Yuan1, SUN You-wen1*, XIE Pin-hua1，2, LIU Cheng2, LIU Wen-qing1，2, LIU Jian-guo1，2, LI Ang1, HU Ren-zhi1, WANG Wei1, ZENG Yi1. Quality Optimization Method for Ambient CO2 Inversion of High Resolution Fourier Transform Infrared Spectrum. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2017, 37(01): 48-53.
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