High-time resolution measurements of atmospheric methane by use of cavity enhanced absorption spectroscopy

采用腔增强吸收光谱（CEAS）技术，研制了一种基于激光的大气甲烷精确测量仪器。开发的仪器的检测限达到1 ppb / 1秒的信号平均，足以实时检测大气中的甲烷。利用该仪器在日本滋贺县的一片日本柏林中，研究了林冠上和林冠内甲烷的时空变化规律。利用自动室内测量系统与激光仪器相结合，计算了叶片、树干和森林土壤与大气之间的甲烷交换通量。以15分钟的时间分辨率获得腔室通量。

A laser-based instrument using a technique of cavity enhanced absorption spectroscopy (CEAS) was developed to measure atmospheric methane accurately and precisely. The limit-of-detection of the developed instrument achieved 1 ppb for 1 second signal averaging, which is enough high to detect atmospheric methane on a real-time basis. The instrument was utilized in a Japanese cypress forest in Shiga prefecture, Japan, to investigate the spatio-temporal behavior of methane above and within the forest canopy. An automated chamber measurement system was coupled to the laser-based instrument developed in this study, thereby methane exchange fluxes between the foliage, trunk, and forest soils and the atmosphere were calculated. The chamber fluxes were obtained with 15-min time resolution.