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

本文研制了一种利用近红外光谱分析仪测量二氧化碳和甲烷柱平均混合比的新系统。我们对波长分辨率和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，估计分辨率达到了期望值。接下来，我们开发了一个程序来检索柱平均混合比从观测光谱。仿真结果表明，从信噪比为500的频谱中可以获得精度在1%以内的混合比。我们将系统获得的混合比与高分辨率FTIR系统进行了比较，发现我们系统获得的强度波动估计在3%左右，没有达到期望值。我们将改进光纤和狭缝系统的挂载机制来解决这个问题。

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.