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

本文介绍了一种用近红外光谱分析仪测量CO_2和CH_4柱平均混合比的系统。我们做了评估的仪器参数，如波长和灵敏度的分辨率，并已发现，估计的分辨率达到预期值，如果我们使用的光纤与狭缝的边缘。接下来，我们开发了一个程序，从观测到的光谱中检索列平均混合比。仿真结果表明，我们可以从信噪比为500的频谱中恢复出精度为1%的混合比。我们已经与高分辨率FTIR系统得到的混合比进行了比较，发现我们的系统得到的强度的波动估计为约3%，这是没有达到预期的值。我们将改进光纤和狭缝系统的安装机构来解决这个问题。

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.