Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH4 and CO2
Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH4 and CO2
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DOI：
10.5194/amt-6-1095-2013
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发表时间：
2013-01-01
影响因子：
3.8
通讯作者：
Perciyal, C. J.
中科院分区：
文献类型：
--
作者：
O'Shea, S. J.;Bauguitte, S. J. -B.;Perciyal, C. J.
高分辨率的CH4和CO2测量是在FAAM BAe-146英国（机载大气测量设施，英国航空航天-146）大气研究飞机上进行的。该系统基于红外光谱仪，采用腔增强吸收光谱技术。通过实验室实验推导了将光谱反演的摩尔分数转换为干空气摩尔分数的修正函数，并在3个月的时间内显示出良好的稳定性。使用WMO（世界气象办公室）可追踪的校准气体监测系统的长期性能。在第一年的运行（29次飞行）中，对系统的飞行校准分析表明，其CH4的测量精度为1.28 ppb (1 Hz下的1 σ可重复性= 2.48 ppb)， CO2的测量精度为0.17 ppm （1 Hz下的1 σ可重复性= 0.66 ppm）。该系统被发现是稳健的，没有主要的运动或高度依赖可以在测量中检测到。通过空腔衰荡光谱分析飞行后的CH4和CO2全空气样本的相互比较表明，两种技术的CH4和CO2的平均差异分别为-2.4 ppb （l sigma = 2.3 ppb）和-0.22 ppm （l sigma = 0.45 ppm）。2012年9月，作为SAMBBA项目（南美生物质燃烧分析）的一部分，该系统被用于对巴西的生物质燃烧羽流进行采样。从这些和同步的CO测量中，计算了大草原火灾的排放因子。CH4和CO2分别为2.2 +/- 0.2 g （kg干物质）（-1）和1710 +/- 171 g （kg干物质）（-1），这与文献中先前的估计非常吻合。
High-resolution CH4 and CO2 measurements were made on board the FAAM BAe-146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity-enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry-air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO (World Meteorological Office) traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to 1.28 ppb (l sigma repeatability at 1 Hz = 2.48 ppb) for CH4 and 0.17 ppm (l sigma repeatability at 1 Hz = 0.66 ppm) for CO2. The system was found to be robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole-air samples that were analysed post-flight for CH4 and CO2 by cavity ring-down spectroscopy showed a mean difference between the two techniques of -2.4 ppb (l sigma = 2.3 ppb) for CH4 and -0.22 ppm (l sigma = 0.45 ppm) for CO2. In September 2012, the system was used to sample biomass-burning plumes in Brazil as part of the SAMBBA project (South AMerican Biomass Burning Analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2 +/- 0.2 g (kg dry matter)(-1) for CH4 and 1710 +/- 171 g (kg dry matter)(-1) for CO2, which are in excellent agreement with previous estimates in the literature.