研究目的
Investigating the feasibility of a remote, multi-path system using Chirped Laser Dispersion Spectroscopy (CLaDS) for quantification of atmospheric methane concentrations over extended areas.
研究成果
The study demonstrated the feasibility of a CM-CLaDS system for open-path sensing of atmospheric methane over multiple sampling paths covering a large area footprint. Despite challenges, the system was able to investigate larger-scale methane trends such as diurnal cycles, the influence of wind dynamics and transport, as well as emissions from different sample paths of various plant species.
研究不足
The system experienced relatively larger temperature swings than planned, which affected the calibration signal and the precision of the sample channel. The main source of drift in long-term measurements was a parasitic fringe between the photodetector window and the telescope body.
1：Experimental Design and Method Selection:
The study utilized Chirped Laser Dispersion Spectroscopy (CLaDS) for remote sensing of atmospheric methane. The system was designed to operate in a multi-path configuration to cover extended areas.
2：Sample Selection and Data Sources:
The field test was conducted at Sallie’s Fen Environmental Station (SFES), a site monitored for methane emissions. Six retro-reflectors were mounted in a star-like configuration ~20 m away from the sensor cabinet.
3：List of Experimental Equipment and Materials:
The system included a weatherized, temperature-controlled cabinet, a gimbal mounted mirror system, retroreflectors, and a weather station (Davis Vantage Pro2).
4：2). Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Each optical path was probed for two minutes, after which the gimbal position was changed to target the next reflector in the cycle. An active alignment procedure with raster-scanning algorithms was developed to realign the system.
5：Data Analysis Methods:
The data was corrected for temperature dependence of the molecular transition and for temperature induced pressure changes within the sealed gas cell.
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