采用加权函数修正的差分光学吸收光谱反演环境大气中的CO2垂直柱浓度

采用加权函数修正的差分光学吸收光谱技术(weighting function modified differential optical absorption spectroscopy, WFM-DOAS)测量环境大气中的CO₂垂直柱浓度. 以直射太阳光测量光谱为例, 演示了WFM-DOAS算法的实现过程. 将环境大气分为50层, 借助辐射传输模拟软件SCIATRAN对各个测量光谱进行了模拟计算, 获得了最小二乘法拟合所需的目标气体CO₂及干扰气体H₂O、CH₄ 的柱权重函数和太阳归一化光谱常量. 采用WFM-DOAS方法对一整天的直射太阳光测量光谱进行了反演, 得到的反演误差均小于3%. 最后比较了两种不同DOAS算法对同一条测量光谱的反演结果, 验证了WFM-DOAS算法在红外被动气体遥感的优越性.关键词：环境污染监测光学测量技术红外光谱温室气体

Measurement of atmospheric CO2 vertical column density using weighting function modified differential optical absorption spectroscopy

In this paper, we demonstrate a method of atmospheric CO₂ vertical column density (VCD) retrieval by using weighting function modified differential optical absorption spectroscopy (WFM-DOAS). Direct sun measurement serves as an example for WFM-DOAS fitting. The atmosphere is divided into 50 layers in the process of WFM-DOAS retrieval, while the simulated sun-normalized radiance and the total weighting functions (CO₂, H₂O and CH₄) for each measurement are computed in terms of the radiative transfer model (RTM) SCIATRAN by using the HITRAN data base and the solar spectrum from Livingston and Wallace (1991). The CO₂ vertical column density time series were obtained by utilizing WFM-DOAS fitting method to all direct sun measurement spectra. Fitting errors are all less than 3%. Fitting results for two different DOAS algorithms are compared with each other. It is indicated that the WFM-DOAS technique has the potential of being applied in passive gas remote sensing in the infrared region.
Keywords：environmental pollution Measurementsoptical measurement techniquesinfrared spectrumgreenhouse gas