Development of a measuring system of column-averaged mixing ratio of greenhouse gases with an optical spectrum analyzer operated in near infrared region

我们新研制了一套二氧化碳和甲烷的柱平均混合比测量系统，该系统带有工作在近红外区域的光谱分析仪。我们对波长分辨率、灵敏度等仪器参数进行了评估，发现如果使用边缘有狭缝的光纤，则估计的分辨率达到了预期值。接下来，我们开发了一个程序，可以从观察到的光谱中检索柱平均混合比。仿真结果表明，从信噪比为500的频谱中提取混合比的精度不超过1%。我们将我们的系统得到的混合比与高分辨率FTIR系统进行了比较，发现我们的系统获得的强度波动约为3%，没有达到预期值。为了解决这一问题，我们将改进光纤和缝隙系统的安装机构。

We have newly developed a measuring system of column-averaged mixing ratio of carbon dioxide and methane with an optical spectrum analyzer operated in near infrared region. We made an evaluation of the instrumental parameters such as a resolution in wavelength and sensitivity, and have found that the estimated resolution was achieved to an expected value if we used an optical fiber with a slit at the edge. Next, we developed a program to retrieve a column-averaged mixing ratio from an observed spectrum. Simulation results showed that we can retrieve the mixing ratio within an accuracy of 1% from the spectrum whose signal-to-noise ratio is 500. We had made a comparison between the mixing ratio obtained with our system and a high-resolution FTIR system, and have found that fluctuation of the intensity obtained with our system was estimated to be about 3%, which is not achieved to the expected value. We will improve a mount mechanism of the fiber and slit system to resolve this problem.