基于比值法的大气CO_(2)反演与地表反射率分析

Atmospheric Carbon Dioxide Inversion and Surface Reflectance Analysis Based on Ratio Method

二氧化碳(CO_(2))是造成温室效应的气体之一,其浓度的空间分布对气候预测和人类生产、生活的影响不可忽视,实现CO_(2)浓度的准确反演有利于掌控全球CO_(2)时空分布。但是在近红外波段,地表反射率的不确定对CO_(2)浓度反演存在影响。引入比值法对卫星对地辐射光谱进行处理,验证吸收波段辐亮度比值与CO_(2)浓度之间存在某种关系,该关系反演CO_(2)浓度具有可行性。以MODTRAN4仿真的辐亮度光谱为数据源,选取4个特征吸收峰的光谱辐亮度比值与CO_(2)浓度进行分析。结果显示,光谱辐亮度比值与CO_(2)浓度存在近似线性关系,而且在6310 cm^(-1)处的线性关系更为明显,误差仅有1.15%。然后通过设置不同的大气模式和气溶胶模式,进一步对辐亮度比值与浓度之比进行剖析,结果表明,在0.1~0.9反射率区间,两者呈高度相关,相关系数高达0.98,平均误差不超过2%。最后对实测数据进行相同处理,与仿真数据进行了对比。在4个波段的拟合中,6334 cm;处拟合效果最好,线性关系达到了0.99,从另一方面说明了光谱辐亮度比值与CO_(2)浓度存在线性关系,这种关系可以很好地应用于CO_(2)浓度的反演,近似消除地表反射率影响。

One of the gases responsible for the greenhouse effect is carbon dioxide(CO_(2)).For climate prediction,human production,and human life,the spatial distribution of CO_(2)concentrations must be considered.Controlling the spatial and temporal distribution of CO_(2)worldwide requires an accurate inversion of CO_(2)concentrations.However,in the near-infrared band,surface reflectance uncertainty affects the inversion of CO_(2)concentration.The ratio method is introduced to process the satellite ground-to-ground radiation spectrum,and it is verified that the absorption band radiance ratio and CO_(2)concentration are related;moreover,inverting the CO_(2)concentration using the relationship is feasible.The data source was the MODTRAN4-simulated radiation spectrum,and the four absorption peaks’spectral radiance ratio and CO_(2)concentrations were selected for analysis.The results show that the spectral radiance ratio and CO_(2)concentration have an approximately linear relationship,and the linear relationship is evident at 6310 cm^(-1),with an error of only 1.15%.The ratio of radiance ratio to concentration is further investigated using various atmospheric and aerosol models.The results show the radiance ratio and concentration are highly correlated in the range of 0.1-0.9 reflectivities,the correlation coefficient is up to 0.98,and the average error is less than 2%.The measured data is subjected to the same processing as the simulation data,and the results are compared with simulated data.The linear relationship at 6334 cm;is the best among the four bands,and the linear relationship reaches 0.99.It shows that the spectral radiance ratio and CO_(2)concentrations have a linear relationship,and this relationship can be effectively applied to the inversion of CO_(2)concentration,effectively eliminating surface reflectance.