基于高分辨率激光外差光谱反演大气CO2柱浓度及系统测量误差评估方法

Atmospheric CO2 column concentration retrieval based on high resolution laser heterodyne spectra and evaluation method of system measuring error

利用实验室研制的近红外激光外差光谱仪,开展了基于最优估计算法的温室气体柱浓度反演和系统测量误差的近似评估等相关工作.首先,通过光谱数据库、参考正向模型计算结果与傅里叶变换红外光谱技术探测结果筛选出了探测窗口,并以此为依据选择了相应的激光器和探测器;其次,建立了基于参考正向模型最优估计浓度反演算法,采用Levenberg-Marquardt(LM)迭代方法,实现了整层大气CO2柱浓度及垂直分布廓线的反演,并开展了长期观测对比实验,验证了反演算法的可行性;最后,通过模拟所选探测窗口波段在不同白噪声条件下的正向大气透过率谱,获得了系统SNR与柱浓度测量误差之间的近似对应关系.该研究是探测系统不可或缺的理论计算部分,将有助于完善激光外差技术在大气探测中的应用.

In this paper,a near-infrared laser heterodyne spectrometer developed by the laboratory is used to investigate the inversion of greenhouse gas column concentration and approximately evaluate the system measurement errors based on the optimal estimation algorithm.Firstly,the spectral database and the calculation results from the reference forward model are compared with the ground-based FTIR results,thereby selecting the detection window,the corresponding laser and detector.Secondly,the optimal estimation concentration inversion algorithm based on the reference forward model is established,and the Levenberg-Marquardt(LM)iterative method is adopted to realize the inversion of the concentration and vertical distribution profile of atmospheric CO2 column in the whole layer,and the long-term observation comparative experiment is carried out to verify the feasibility of this algorithm.Finally,by simulating the selected detection window spectrum in different white noise,the approximate corresponding relationship between the system signal-noise-ratio(SNR)and CO2 column concentration measuring error is eventually obtained.This research is an indispensable theoretical calculation part of the detection system and will conduce to improving the application of laser heterodyne technology in atmospheric observations.