地表反照率对短波红外探测大气CO2的影响

Effects of the surface albedo on short-wave infrared detection of atmospheric CO_2

在卫星短波红外遥感二氧化碳的过程中,表征地表特征的地表反照率是影响探测精度的重要参数之一.针对温室气体二氧化碳高精度探测的需求,本文研究了地表反照率对正演模拟光谱和反演近地面二氧化碳平均柱浓度XCO_2的影响.模拟计算结果显示,地表反照率数值增大时,观察的光谱强度也相应增大,并且在O_2-A波段造成的光谱差异比1.6μm波段高出一个数量级,即地表反照率在O_2-A波段的影响比较大.选取了两个不同地表类型的实际观测光谱,仅改变O_2-A波段和1.6μm波段地表反照率数值,得出草地点在O_2-A波段地表反照率达到0._25的误差时,会给XCO_2的反演结果造成大于1%的相对误差,而1.6μm波段的地表反照率变化对XCO_2的反演结果造成的误差可以忽略不计,说明了地表反照率在反演XCO_2过程中的重要性主要来自对O_2-A波段的影响.此研究表明了地表反照率在卫星遥感温室气体过程中的重要性,为提高遥感探测二氧化碳的精度提供了重要的理论依据和指导.

The greenhouse gas carbon dioxide,for which short-wave infrared remote sensing detection is carried out by using satellite sensors to measure the Earth’s atmosphere scattering solar radiation,and makes use of the inversion algorithm to achieve measurements.Most of the solar radiation enter the satellite sensors after surface reflection,so the surface albedo which reflects the surface features is one of the important parameters which affect the accuracy of the detection.Aiming at the great demands of high precision carbon dioxide for greenhouse gas,this study first investigate the effects of the Earth’s surface albedo on the observed spectra.Simulation results show that the increase in the surface albedo will enhance the observed spectral intensity,especially larger in the O2-A band than in the 1.6 μm band.In other words,the surface albedo has a greater impact on O2-A ban.In the actual satellite inversio,the surface types of actual observation pointare uncertain,which will result in the error of surface albedo.Effect of surface albedo on the inverted XCO2 is analyzed when the surface albedo is changed by changing the type of surfac.Two observation cases are analyzed in detail.One is on April 23,2009 for the desert surface,and another on May 21,2013 for the grass surfac.Results show that when the O2-A band surface albedo approximates to the real surface albedo valu,the relative error of the inverted XCO2 is the smaller.If the relative changes of the O2-A band surface albedo exceed 0.25 in the grass surfac or 0.35 in the desert surface,the relative error of the inverted XCO2 will be greater than 1%,not satisfying the design requirement of the inversion system.In contrast,the changesin 1.6 μm band surface albedo have negligible effect on the inverted XCO2.This study shows the importance of surface albedo in the process of satellite remote sensin,and provides an important theoretical basis and guidance for improving the accuracy of remote sensing detectio.All these are significantly contributed to the hyperspectral satellite observation of the greenhouse gas,the investigation of global CO2 distributions,and the prediction and monitoring of the climate change.